Contact Tracing and Outbreak Response

Contact TracingCopy Link!

What is Contact Tracing?Copy Link!

Updated: February 1, 2021

Definition: Contact tracing is a process through which we can break chains of COVID-19 transmission, connect people to care, and identify clusters or outbreaks.

A comprehensive contact tracing program includes: conducting case investigation, identifying known exposed contacts, providing support for both positive cases and exposed individuals to safely isolate or quarantine until no longer infectious, and connecting unvaccinated individuals with vaccination resources.

Each person who is newly diagnosed with COVID-19 as a “case” is interviewed to enumerate their close contacts, e.g. those who have been within six feet for 15+ minutes over a 24-hour period. Those people who are identified as close contacts are notified and entered into a care management system, so that they can:

  1. Stay in safe quarantine according to CDC guidelines, supported by resources to protect themselves and their families
  2. Be tested for COVID
  3. Be monitored for symptoms

This process is the prospective component of contact tracing. Another important aspect of case investigation is called “source investigation”, or understanding where the person may have been infected with COVID-19. This is also called retrospective tracing. It is an important part of identifying clusters and is discussed further in Outbreak Response.

Contact tracing is not new for Departments of Public Health in the US. Local health departments have historically conducted contact tracing for other diseases, such as tuberculosis and sexually transmitted infections, but additional support is essential to manage the volume of cases and contacts associated with the novel threat of COVID-19. COVID-19 is also rapidly transmissible and can cause large outbreaks and move through communities quickly, introducing a higher degree of time pressure to testing and tracing than with some other conditions.

Contact tracing is a core public health tool used to respond to infectious disease outbreaks. It was identified early on as a way to combat COVID 19. Contact tracing, supplemented with community protection strategies, widespread testing, supported isolation and quarantine, and vaccination are the essential components of an effective pandemic response and of the broader public health toolkit for epidemic control and care delivery.

Previous contact tracing efforts:

  • Contact tracing helped prevent Ebola from spreading in other West African countries during the 2014-2016 outbreak. Studies describe the importance of contact tracing in also identifying gaps that can be addressed for future response.
  • Contact tracing was one of several interventions that helped control the SARS epidemic in 2003.
  • Contact tracing was a core component of smallpox eradication and is frequently used for HIV, STIs, and tuberculosis.

Contact Tracing in COVID-19Copy Link!

Since people can transmit COVID before or without symptoms, contact tracing combined with quarantine is most effective.

Evidence supporting contact tracing in COVID-19 includes:

Contact tracing is not only a purely epidemiological exercise to stop the spread of COVID-19, but also a care exercise that connects cases and contacts to social and material support. Given the potential logistical, emotional, and financial difficulties of quarantining or isolating for several days, effective contact tracing programs must also be able to connect cases and contacts to food, housing, medicine or other needs that arise over the quarantine and isolation period, like diapers or rent. Without contact tracing programs that can provide social support, people will have to choose between quarantining to stop the spread or continuing with their daily lives, thus perpetuating the pandemic. The inability to quarantine or isolate without direct support disproportionately affects poorer people and communities of color. Incorporating social support mechanisms into contact tracing programs also introduces the possibility of connecting cases and contacts to longer term support programs. This could include long-term enrollment in benefits programs for food, rental assistance or housing, or other resources in their community.

Core ElementsCopy Link!

Effective contact tracing programs are guided by four core elements:

  1. Technical expertise: Effective contact tracing programs that successfully reach cases and contacts require epidemiological knowledge, logistical capacity, clinical support guidelines, robust training and mentorship programs, and program management expertise. Programs should be set up by or in conjunction with public health departments.
  2. Adequate Staffing: Without adequate staffing and flexibility, contact tracing programs will be unable to flex up and down as the course of the disease changes. A nimble, trained workforce is necessary to create an effective contact tracing program.
  3. Leadership: In order to implement a contact tracing program at the state or local level, effective government leadership is necessary to champion and manage the program, combat misinformation, build community buy-in, and properly finance tracing efforts.
  4. Equity agenda: Equity must be built into any COVID-19 contact tracing program to combat the systemic racism that puts Black, Latinx, and Native American populations at a higher risk of contracting the virus and suffering poor outcomes including death; these populations also have higher needs for social support in order to safely quarantine or isolate. Contact tracing programs must address these needs.

Governance and PartnershipsCopy Link!

  • Building a robust COVID-19 contact tracing program requires high-level political support and significant resources.
  • COVID-19 contact tracing programs should be integrated within or in close partnership with public health departments who know the context of a region and have been doing this work for years. Contact tracing programs should amplify the existing work of local public health departments rather than centering themselves as the primary source of knowledge.
  • Strong leadership and buy-in at both the senior policymaker and programmatic levels is necessary to a successful contact tracing program. Without buy-in and political will at the highest level, contact tracing programs will often fail to achieve public buy-in or meet funding needs. Strong technical and operational leadership at the program level is needed to guide rapid decision-making about the evolving demands on CT programs.
  • Contact tracing programs should be well integrated within a state or local jurisdiction’s larger public health response to COVID-19, with strong operational integration and strategic alignment with testing, mitigation policy, supported isolation/quarantine and vaccine rollout efforts.
  • Clear definition of roles, responsibilities and decision rights are essential within complex partnership structures supporting contact tracing; a regular review and adaptation of governance arrangements is essential to keep up with rapidly evolving epidemic dynamics and partner ecosystems.

Roles and WorkflowsCopy Link!

An overview of the contract tracing process can be found here.

Key ComponentsCopy Link!

Effective contact tracing programs include 6 pillars. Some programs include all pillars within a central program, others rely on close partnership with separate workstreams:

  • Testing – Testing should be widespread and decentralized. A successful and timely contact tracing program relies on tight coordination with testing in order to quickly contact anyone who has tested positive for COVID-19 and to refer contacts for testing.
  • Case Investigation is the first step in the process after an individual is diagnosed with COVID-19, Case investigation involves interviewing a newly diagnosed person with COVID-19 to enumerate their contacts, ask about exposure details, monitor their symptoms over time, and ensure ability to safely isolate throughout their illness and provide connections to social support.
  • Contact Tracing – After cases identify their contacts, contact tracing involves contacting and interviewing those people identified as exposed contacts through case investigation, and monitoring their symptoms, recommending testing, ensuring their ability to safely isolate throughout quarantine and provide connections to social support.Contacts of positive cases should all be referred to testing.
  • Safe Isolation/Quarantine and Care Coordination – In order to successfully isolate/quarantine, CT programs need a coordinated approach to care and social support. Cases and contacts should be screened for social needs during case investigation and contact tracing. Some will require support to safely isolate or quarantine, and programs should mobilize or refer to different social resources including food, housing, transportation, economic support, and mental health and addiction resources.
  • Outbreak Investigation – As case investigators uncover sources of exposure through source investigation, contact tracing programs are often the first source of information that a cluster may exist. This can trigger further investigation of the cluster and the outbreak response.
  • Vaccination Resources -- COVID-19 identifies pockets of unvaccinated individuals, spreading more easily through unvaccinated populations than those that are vaccinated. By coupling contact tracing with vaccination resources, individualized education is provided to unvaccinated cases and contacts, followed by their connection to vaccination resources if willing. This also helps to prevent future outbreaks and severe disease.

Workforce considerations are described below.

Contact Tracer RolesCopy Link!

Contact tracers and case investigators are expected to provide a number of services to cases and contacts, including health education on COVID-19; collection of demographic, clinical and exposure information; isolation and quarantine advising; and resource assessment.

  • Education – What is COVID-19? How is it spread? What are the symptoms? How can I keep myself and my community safe and healthy? ​
  • Epidemiological Data Collection – Demographic information; clinical information (symptoms, hospitalizations, etc.); exposure information (to identify clusters/multiple exposures); contacts; resource assessment ​
  • Advising on Isolation/Quarantine – Importance of isolation for positive cases; importance of testing/quarantine for contacts; regular follow up and monitoring of symptoms; eventual clearing of people from isolation/quarantine​
  • Assessment for and Connection to Social Needs – Resource assessment during initial intake; continued assessment during follow up calls; liaising with community partners/care resource coordinators to arrange for resource delivery​

WorkflowsCopy Link!

Contact tracing includes definitive workflows between all pillars of the COVID response, including testing, treatment, and social support. This contact tracing workflow (page 13) can serve as a model for contact tracing programs creating their own workflows.

Care Resource CoordinationCopy Link!

Care resource coordination (CRC) is the process of identifying the needs and providing the social, material, and other supports needed to allow cases and contacts to safely isolate or quarantine. Social determinants of health and disparities in health outcomes are exacerbated by the fragmented social support landscape in the U.S. and care resource coordination is a must-have to address this problem. Many cases and contacts cannot isolate or quarantine without support.

CRC work is needed because:

  • Isolation (cases) and quarantine (contacts) break the chain of COVID-19 transmission.
  • For cases and contacts to isolate and quarantine for 7-14+ days, support systems need to be in place to allow for everyone to quarantine and isolate safely and effectively. Without ensuring that everyone can quarantine and isolate safely, people may be forced to choose between meeting basic needs and quarantining, thereby perpetuating the pandemic.
  • CRC work is essential to address health-related social needs and social determinants of health that directly impact individual health outcomes and population health.

Integrating with Contact TracingCopy Link!

Tool: PIH guide on the Components of CRC Programs

  • Case investigators and contact tracers should complete an initial needs identification for all cases and contacts.
  • Anyone with support needs should be referred to a care resource coordinator and a more detailed needs assessment is conducted.
  • CRCs then refer to or provide resources, using warm handoffs and ensuring linkage, in order to support cases or contacts to isolate/quarantine safely. CRCs also help connect individuals to those who can link them to long term benefits if needed.
  • Regular follow-up is required to assure additional resources are provided when necessary and symptoms are monitored.

Best PracticesCopy Link!

  • Screening for social support should be done early and often. Screening should start at testing sites and support should be offered throughout quarantine and isolation at regular intervals. All contact tracing staff should be trained to ask these questions in a non-threatening and culturally appropriate way as well as understand the variety of the types of support people may need.
  • CRCs should have local experience and work closely with local partners in order to properly connect cases and contacts with the necessary resources. Diverse language abilities are necessary to reach everyone who may be infected.
  • Establish clear referral protocols and lists of social support resources. Incorporate screening questions into contact tracing scripts. Ensure contact tracers and case investigators are trained on requirements for isolation/quarantine, common social needs, specific needs assessment scripts, and how to refer patients to a CRC.
  • The overarching goal of care resource coordination is linkage to care, but linkage assumes supply. Creative solutions are required to ensure sufficient referral pathways, including adaptive systems to facilitate referrals between CRCs and community based organizations and updated resource databases organized geographically and thematically.
  • Flag potential clusters for outbreak investigations. These clusters often identify pockets of unvaccinated individuals, who can then be connected with education, testing, and vaccination resources.

Workforce and TrainingCopy Link!

Key Roles and ManagementCopy Link!

There are three primary roles within a contact tracing program: case investigators, contact tracers, and care resource coordinators.

  • Case investigators engage with newly diagnosed COVID-19 patients, explain diagnosis and facilitate safe isolation; offer assistance; identify people they may have exposed to the virus (contacts); collect key information about the person; identify where the person may have been exposed and if they could be part of a cluster.
  • Contact tracers engage with the contacts of people diagnosed with COVID-19; explain their risk of infection and of transmitting the disease; assess symptoms; explain and facilitate safe quarantine; assess support needs; collect key information about the person.
  • Care resource coordinators engage with COVID-19 patients and their contacts to understand their resource needs to safely quarantine and isolate; connect them to essential material, financial, and social supports.

Programs should strive to combine the case investigator and contact tracer roles into one cross-trained role. This is for two major reasons: (1) to build a nimble workforce that can withstand large fluctuations in cases and contacts as the pandemic ebbs and flows and (2) to prepare employees for inevitable household transmission that requires them to speak to cases and contacts in the same phone call.

Support structures are necessary to manage the workforce of case investigators, contact tracers, and care resource coordinators, promoting productivity and wellbeing as well as improving program metrics and design.

  • Management and Leadership Team: Responsible for oversight and accountability of the program, as well as troubleshooting. Consists of program leadership, responsible for implementation & design, data, strategy, policy, communications, HR, clinical, and coordination with the government and DPH. Should continuously track program metrics to improve program efficacy.
  • For a contact tracing program to properly respond to an evolving pandemic and manage ongoing programmatic issues, a strong workforce management team must lead the program.
  • Training Team: Responsible for training all new CIs/CTs/CRCs and offering continued education for all employees. Training programs should be nimble and tightly connected to implementation updates.
  • Mentors and Peer Support: Given the numerous changing protocols needed in an adaptive CT program, mentors should be continuously available for questions and training of all employees. Peer support programs should be created to offer emotional assistance to employees given the taxing nature of the work.

Adapting to Evolving EpidemicsCopy Link!

Workforce quantification

  • A nimble workforce that can fluctuate in size depending on the course of the pandemic is necessary for a program to be effective. The number of contact tracers and case investigators needed will vary, depending on:
  • The number of new positive tests (cases)
  • The number of contacts per case
  • The average duration for each initial case investigation and contact tracing call
  • The number of follow up calls per case and contact, and their average duration
  • The responsibilities for outbreak investigation and response and linking with businesses or other places where larger exposures may have occurred
  • Workforce estimation tools can be useful to estimate how many CTs/CIs/CRCs are needed at a given time
  • Partners In Health and the Analysis Group created a workforce quantification tool to model the exact number of contact tracers and case investigators needed based on the epidemiological curve of the disease
RecruitingCopy Link!
  • Engage and reinforce existing community health workforce members and cadres, including Community Health Workers, and engage FQHCs as key staffing partners where possible.
  • Prioritize hiring from hardest-hit and most vulnerable communities; ensure recruiting and workforce partners have clear accountability for equity and diversity in hiring.
  • Prioritize hiring of staff with diverse language capacities to address the diverse language needs of your constituency.
  • For call center-based contact tracing programs, recruiting contact tracers with basic to moderate tech skills will increase the speed of training.
  • The program should clearly communicate to recruits the evolving nature of the program based on the spread of the infectious disease and the resulting contract length -- a need for flexibility should be a key component of recruiting.
Surge StaffingCopy Link!
  • Essential to rapidly respond to hotspots and outbreaks
  • Depending on local financing and governance (home-rules vs. more centralized approach to public health), options for how to ramp up surge staffing vary; approaches include:
  • Hire a centralized surge workforce to be deployed upon request to local departments, or operate virtual call centers with full statewide coverage
  • Provide grant funding to local health departments to hire and manage surge staff locally
  • Contract local CBOs to provide local health department staff with surge support

Community EngagementCopy Link!

ApproachCopy Link!

  • Contact tracing communications campaigns should be hyperlocal with connections to local leaders and influencers.
  • Building trust and sharing knowledge are the most important goals of any communications program.
  • Information should be accessible to everyone in a community – extensive multi-media campaigns, broad coalitions of community organizations, and engagement in representative languages are needed.
  • Information should be thoughtfully placed in relevant parts of the process, meaning the places people will likely go before being called by a case investigator if they do test positive (e.g. clinical officers, testing sites, etc.).

GoalsCopy Link!

  • Generate awareness about contact tracing.
  • Dispel misinformation by pointing the public to official and comprehensive sources of verified facts.
  • Rebuild trust in the public healthcare system among communities that have been historically marginalized.
  • Destigmatize COVID-19 by ensuring cases and contacts feel safe when they are contacted and are comfortable sharing their contacts.
  • Communicate that contact tracers are calling to help, connect people to medical services and social supports; they are not authority figures seeking to get them in trouble or affecting their immigration status.

StrategiesCopy Link!

  • All community engagement and education should be available in local languages.
  • Communicate with faith-based organizations and work with religious leaders to educate communities and build trust.
  • Partner with community organizations and support public events (e.g. food distributions, education sessions, etc.).
  • Coordinate with the DPH for events and campaigns around health promotion (e.g. mobile testing, flu vaccination).

Best PracticesCopy Link!

  • Public-facing communications for contact tracing programs should include multi-channel media campaigns in order to reach the highest number of people (i.e. TV, radio, Facebook/Instagram, Google Ads, and town halls).
  • Programs should develop partnerships at the community level (i.e. mayors/local councils, health centers, community centers, faith groups, immigrant groups, school superintendents, food pantries, etc.) in order to build trust and combat disinformation.
  • Anticipate transmission events and conduct proactive outreach to high risk locations to build trust, reinforce communication, and encourage safe practices (ex. Places of Worship ahead of religious holidays, bars ahead of St. Patrick’s Day/New Years, etc.).
  • All media should be developed in local languages and delivered at a hyper-local level (i.e. grocery stores, churches, etc.).
  • Consider working with communications companies (cell providers) for increased visibility on CallerID/getting through mobile spam filters.

Metrics and MonitoringCopy Link!

Defining and Tracking SuccessCopy Link!

Metrics should guide every contact tracing program in improving quality and ensuring program effectiveness

  • Collecting comprehensive data and ensuring quality reporting and dashboards are essential to monitor delivery across 4 key dimensions of an effective program: Scale, Speed, Retention, and Equity.
  • Demographic metrics provide a profile of the contract tracing program – all key performance indicators (KPIs) should be disaggregated by key demographic variables (i.e. gender, race, ethnicity, and language) and analyzed for differences.
  • All metrics should have defined targets and progress tracked against these targets; leadership should actively manage progress.

Effective contact tracing programs focus on 4 critical dimensions: equity, scale, speed, and retention.

  1. Equity: Are we responding to all unique needs with a social justice lens, and prioritizing the most vulnerable groups? Are CRC referrals at the optimized level?
  2. Scale: Has the response built up the infrastructure to meet demand (e.g., staffing capacity, social support resources)?
  3. Speed: Is the response happening quickly enough to drive the rate of infection below 1: < 3 days for the full cascade?
  4. Retention: Where is loss-to-follow-up occurring at each stage in the cascade (i.e. testing to case investigation to contact tracing to follow-up)?

Example MetricsCopy Link!

Tool: Partners In Health’s COVID-19 Data Evaluation: Metrics and KPIs, Section 3

Example metrics

  • COVID-19 response metrics: # of cases reached, # of cases identified and supported to isolate, # of contacts identified and supported to quarantine, # of educational materials provided
  • Social support metrics: % of individuals identified with resource need, referred, and received resource
  • Clinical support metrics: % of individuals identified with pre-existing conditions in need of healthcare, referred, and connected to clinical care
  • Timing metrics: show how long the entire cascade takes (from time of test to isolation/quarantine) with the goal of <3 days to drive R0 < 1

Tool: Sample Priority Metrics from PIH’s program in Immokalee, Florida

Tool: KPI guidance from PIH - these example key performance indicators (KPIs) provide an example of what contact tracing programs should be measuring and monitoring

Example Monitoring DashboardsCopy Link!

Tool: Partners In Health’s COVID-19 Data Evaluation: Metrics and KPIs, Sections 2 and 4

  • Case investigation metrics track case status and help identify problems in retention and scale
  • Care resource coordination metrics map vulnerability and equity among contacts, particularly demonstrating those who need support to quarantine

Digital and Technology SolutionsCopy Link!

Technology can be deployed at multiple times during the contact tracing process. However, technology requires humans to make it work. Contact tracing is not just an epidemiological exercise, it is an exercise in care that cannot be effective through technology alone.

Key digital and technology solutions for contact tracing include

  • Local epi surveillance systems: These are the systems of records for all communicable diseases. Positive lab tests are received here. COVID cases can then be transferred to the case & contact management platform. Local or state epi systems may not be able to support the scale of COVID-19 contact tracing.
  • Case and contact management platforms (CRMs): CRMs should be able to execute case investigation and contact tracing workflows at scale while collecting and storing data from calls. Data integrity and synchronization between the local epi system and CRM is of utmost importance, as duplicate cases and contacts should be minimized where possible, cases and contacts must be linked to capture the chain of transmission, and case data must be synced rapidly from the epi system to the CRM to ensure swift follow up.
  • Proximity tracking tools: Digital tracking systems, often on mobile devices, are used to determine contact between an infected patient and a user. These programs often use Bluetooth or GPS. In the US, adoption of proximity tracking tools has been slow due to privacy concerns. Notably, these automated tools cannot provide care resource coordination and though they can supplement manual contact tracing, they should not replace it.
  • Medical monitoring tools: These tools enable remote symptoms monitoring and referral to care and testing. Public health departments can enroll at-risk individuals in the app and monitor symptoms based on patient reports. Thus far, there has been limited data on adoption rates and effectiveness. These tools also lack functionality for referral to social support services and must be integrated into the CRM platform to connect patients to care.

Ensuring the privacy of a case and contact data is of the utmost importance. Contact tracing programs will not work if people don’t trust contact tracers to guard their information correctly and safely. Protected health information should only be used in reference to COVID-19 public health and individual care needs.

Tech DecisionsCopy Link!

  • Will the local disease surveillance database be used for the system of record for case data (i.e. MAVEN in MA, NEDSS elsewhere) or will a new system be deployed?
  • What case and contact management platform (CRM) will be used to centralize case investigation and contact tracing workflow (i.e. SalesForce, CommCare)?
  • What will the intersection be between the CRM and the epidemiological surveillance system? How will the CRM or epi system be updated to reflect the unique COVID-19 needs and considerations?
  • Will Bluetooth/GPS proximity tracking or symptom monitoring tools be used widely? If so, how will the contact tracing program interact with those tools?

Systems StrengtheningCopy Link!

Contact tracing systems have the opportunity to effect long-term system change.

  • Build community health programs that can also contribute to long-term healthcare system strengthening efforts
  • Contact tracing programs can build upon existing community health worker programs or become the foundation of a new one
  • Train contact tracers and community health workers to refer and accompany people to clinical care to improve access to healthcare even outside of the COVID-19 pandemic
  • Combine COVID-19 response strategies with other health promotion activities to increase trust in the health care system
  • Flu vaccination, basic primary care services, mobile COVID-19 testing, and COVID-19 vaccination

Outbreak ResponseCopy Link!

What is Outbreak Response?Copy Link!

Updated: October, 2021

An outbreak of a disease is when multiple people are infected through the same source (e.g. workplace, social event, congregate setting) over a short period of time.

An outbreak response comprises all the steps necessary to investigate and contain an outbreak. This comprehensive strategy is designed to stop transmission by focusing on COVID-19 clusters.

  • Outbreak investigation refers to uncovering when and where a case was infected and who else was exposed; mapping out the reach of the cluster including all cases, close contacts, and casual contacts; identifying key areas for risk mitigation
  • Outbreak containment includes all the interventions put into action to suppress a cluster and prevent future ones

Outbreak response addresses both close contacts and casual contacts of infected individuals. True close contacts are at highest risk for COVID-19 infection, but casual contacts can also be at risk for infection and therefore can propagate transmission if not tested following a possible exposure.

  • Close contacts are those who are exposed and typically need to be quarantined (see exposure definition here)
  • Casual contacts are people who do not meet the strict definition of close contact and those who do not need to quarantine but may have been exposed through sharing common spaces. For example, coworkers in a workplace outbreak who likely share airspace, people worshiping at the same church, people who attended the same party, etc.

Core Elements: Effective outbreak responses require a full range of COVID-19 public health interventions including: Contact tracing for cases, care resource coordination for cases and their close contacts in order to support isolation and quarantine, and testing and vaccination. The process as a whole is described in more detail in Core Elements section.

Leadership: Ideally local health departments in conjunction with a well-trained contact tracing program lead outbreak response. (See Governance and Partnerships and Workforce and Training). This could mean the outbreak response team is integrated with the contact tracing workforce, or it could mean they communicate and collaborate with a separate contact tracing force.


  • Equity: COVID-19 finds and thrives in high social vulnerability environments. By bringing essential resources and outreach to high-risk settings where cases are already occurring, the strategy invests in marginalized communities to ensure equity in response.
  • Comprehensiveness and coordination: It unifies key pillars of response (testing, tracing, vaccines, treatment, supported isolation/quarantine), and the same team oversees performance of, or linkage to, each.
  • Efficiency: It identifies locations that have cases for a reason—low vaccination rates, facility features, activities taking place—and targets interventions to them.
  • Impact: By working to identify and contain clusters early, interventions prevent spread in both the immediate setting and in the wider community. It uses existing public health infrastructure and workforce and unifies the outbreak control strategies already in place across the US. As testing volume drops, investigating clusters and intervening is even more critical to identify undiagnosed infections.
  • Flexibility and Adaptability: Easily integrating into varied public health structures, outbreak response teams are part of the solution to the transition from emergency response to long-term systems improvement.

Outbreak Response in COVID-19Copy Link!

Updated: October, 2021

COVID-19 is a clustering disease, and people are believed to be most infectious prior to symptom onset. This results in exposures occurring in workplaces, schools, recreational activities, and other public-facing locations prior to individuals knowing that they are sick.

There are generally two types of COVID-19 outbreaks:

  1. Slower, ongoing chains of transmission.
  1. These are seen frequently in workplaces where extended exposures result in many people being exposed, often even despite best efforts to implement protective measures. These outbreaks can produce several cases each week and span over the course of weeks or months.
  1. Larger, more explosive outbreak events.
  1. These can also occur in workplaces, but are frequently seen in public-facing locations, such as restaurants or night clubs, and other high-risk exposure activities, such as youth sports and recreational activities where exertion and heavy breathing may increase exposure risk or where preventive measures are more difficult to implement.

Outbreak Response and EquityCopy Link!

COVID-19 has and will continue to exploit vulnerability within communities, exacerbating existing inequities. By focusing on outbreaks, teams can tailor their response to meet the needs of specific communities, especially vulnerable communities. This often includes unvaccinated pockets of people, and because an outbreak occurred within a community once, renders it at risk for another outbreak. Outbreak response is an opportunity to vaccinate entire communities and social networks as well as mitigate other risks, before an outbreak can occur again.

Core ElementsCopy Link!

Updated: October, 2021

There are four core elements of outbreak response:

  1. Testing: A wide net should be cast when recommending and facilitating testing for those linked to a cluster, including close and casual contacts and response workers (including the outbreak team and anyone involved who is liaising with the communities, businesses, local health departments, mayoral offices, etc who are involved in the effects of or the response to the outbreak). Those who test positive will enter the contact tracing program, where source investigation will take place. A process should be in place to be able to record, and include for investigations, home-based rapid test results. Mobile testing units, knowledge of nearby testing locations, and education for organization leaders are all good cluster-based testing strategies.
  2. Contact Tracing: Additional contacts discovered through cluster investigation should be entered into the contact tracing program.
  3. Tactical vaccination: Tactical vaccination involves deploying vaccination efforts specifically to people and communities who are part of an outbreak (close and casual contacts, or other connected people who may be at risk of the outbreak, e.g. place of employment, place of worship, other places with shared airspace, etc). Tactical vaccination often focuses education and outreach efforts on people who are unvaccinated or under-vaccinated, as they are most likely to become infected and infectious in the short- and long-term. It can open up entire social networks who need access to vaccination. Tactical vaccination can be supported through mobile vaccination units, helping people register for vaccines, and educating individuals and trusted authorities linked to the cluster.
  4. Social support services: Those infected with or exposed to COVID should be connected to support services if they need help with accessing testing, resources for safely isolating/quarantining, or vaccines. Because outbreaks tend to occur in vulnerable populations, incorporating resource coordination can connect people to the social safety net and – for example – reduce food insecurity by enrolling families in SNAP (previously called food stamps) and connecting them to food banks.

Comprehensive Outbreak ResponseCopy Link!

Updated: October, 2021

A comprehensive outbreak response will include additional epidemiological, clinical, and public health measures to ensure the full scope of the outbreak is understood, contained, and future outbreaks are mitigated.

  • Sequencing: Where possible, all positive test samples should be sequenced for variants. This is especially important for clusters in communities with known or suspected variants or unusual outcomes. Sequencing can also be used to associate additional cases with clusters or even form the basis of detection of clusters when sequencing data is available in real time.
  • Therapeutics: Link people infected with or exposed to COVID, especially those at risk of severe outcomes, to monoclonal antibody therapy (as therapy or prophylaxis). This is a promising prevention method that is becoming more widely accessible as it moves from intravenous to injection-based delivery. Outbreak response is an opportunity for early identification of contacts who may benefit from monoclonal antibody therapy and could be directly linked to providers for evaluation.
  • Sector-specific guidance: Guidance tailored to the location should be given, including for ventilation, collection of patron lists, linkage with mobile testing and vaccination services, and other measures that help with cluster prevention and investigation.
  • Community outreach: The outbreak response team should proactively conduct community outreach based on lessons from the cluster investigation and response. This can range from contacting similar locations to recommending preventive measures, talking to trusted authorities in the local community, and providing outreach materials for locations.

Governance and PartnershipsCopy Link!

Updated: October, 2021

While many Local Boards of Health (LBOH) or Departments of Public Health (DPH) are jurisdictional, COVID-19 is not. Communication across LBOHs, and between LBOHs and DPHs, is critical in responding to clusters. The outbreak specialists should be in constant communication with all departments involved in a cluster; the jurisdiction of the cluster event itself and the jurisdictions of residence for each individual exposed or possibly exposed in the cluster event. Depending on the size and scope of the cluster, frequent communication with the DPH is recommended as well.

Throughout the investigation, outbreak specialists can work with the LBOHs to collect close contacts, casual contacts, and provide appropriate guidance to the business owners or hosts of social events. LBOHs can deploy their testing and vaccination resources to identified cluster locations to mitigate spread and future outbreaks. Following the investigation and completion of the cluster response, the outbreak specialists can present a cluster map to local officials involved in the response. These presentations and resulting discussion can help to glean lessons learned and prevent clusters in the same location or similar sectors, and can help guide policy decisions.

In addition to outbreak specialist-identified clusters, LBOHs and other state officials can share tips with the cluster team to get ahead of transmission before significant transmission occurs in high-risk locations.

Strong communication with the Local Health Authorities is critical, but the ability to communicate clearly with business owners and community members is also necessary to ensure swift exposure notifications and recommendations for testing and vaccination.

Workforce and TrainingCopy Link!

Key Roles and ManagementCopy Link!

Updated: October, 2021

Outbreak Response teams can be as small as a few people or large. Some settings will identify ‘flex’ team members from a regionally based pool that can be activated to support local outbreaks when needed.

The key roles of the outbreak investigation team itself include:

  • Outbreak Specialists: Review exposure sources provided by COVID-19 cases; triage exposure sources and identify clusters; collaborate with specialized case investigators to conduct location outreach and exposure notifications; collaborate with Care Resource Coordinators to identify and address social support needs and bottlenecks to testing, treatment, vaccination, and isolation/quarantine; map and document cluster across all cases and contacts; connect cluster location with testing and vaccination resources to prevent future outbreaks; provide guidance and technical support to the location in accordance with local guidelines; record data and metrics around cluster investigation; report to local and state governments swiftly and accurately; where relevant, teach and mentor contact tracing staff on source investigation, epidemiology of clusters
  • The Outbreak Specialists rely on the larger contact tracing workforce. It is critical that the bulk of the contact tracing workforce be trained at least on the basics of source investigation, epidemiological principles of clustering, and basic cluster investigation. The more well trained the contact tracing workforce is, the smaller and more agile the outbreak investigation team itself can be.
  • Specialized Case Investigators: Collaborate with outbreak specialists to support cluster investigations; conduct location outreach for exposure notifications; assist with widespread notification of individuals possibly exposed during outbreaks; explain risk of infection and transmitting COVID-19; connect the location and individuals with testing and vaccination resources
  • Management and Leadership Team: Responsible for oversight and accountability of the team; review metrics to ensure appropriate prioritization; encourage collaborative workflow development and team building; adapt to evolving epidemics; HR and administrative support

These integral additional teams can be integrated within the outbreak response team, or work in partnership with them:

  • Contact Tracing Workforce: The outbreak-specific workforce outlined above relies on a strong contact tracing workforce, including contact tracers, case investigators, and care resource coordination. Communication pathways between these two teams are critical to identify outbreaks as well as clear data priorities and standards on how data is recorded.
  • Care Resource Coordinators: The team providing social support is often embedded within the contact tracing workforce to ensure cases and contacts have the material support they need for isolation/quarantine. Integrating resource coordination within outbreak response is important given the high number of cases/contacts that may be identified, often with a high degree of vulnerability. In addition, specifically putting resource coordination within the outbreak team means that these personnel can assist with community partnerships, navigating barriers to testing, vaccination, and treatment, and work with community partners on culturally appropriate communication strategies (including specific language needs).

WorkflowsCopy Link!

Updated: October, 2021

Tool: Asking about and documenting COVID-19 exposure sources

Tool: Working with COVID-19 exposures in public or crowded locations
Tool: Widespread notification following COVID-19 exposures

Tool: How to make a case map for outbreak investigations

Outbreak response workflows are generally dependent on the level of transmission within the community. Source investigation is critical at all stages of an epidemic, but the specific outbreak-response can be adapted based on high and low levels of COVID-19 community transmission and local prioritization.

At any time, the core workflow elements of outbreak response rely on:

  • Source Investigation: Understanding where COVID-19 comes from is critical to interrupting ongoing chains of transmission and prevent future outbreaks. Source investigation should be conducted with each confirmed, probable, or suspected case of COVID-19, and includes baseline questions case investigators and contact tracers use to assess possible high-risk exposure sources within the 14 days prior to symptom onset. As COVID-19 is a clustering disease, it’s likely that more than one person was exposed at that same exposure event. Source investigation is critical in both high and low transmission settings. An approach for source investigation is included in Asking about and documenting COVID-19 exposure sources
  • Location Outreach: Once an exposure source has been identified, the location needs to be informed as quickly as possible of the potential exposure. Conducting outreach to these locations serves as a touch point with management, the business owner, or other point person for the organization where preventive measures can be reinforced and any misunderstandings can be addressed. Asking general questions, such as ‘how many people have been out sick recently?’ can open wider conversations than individual exposure the outbreak team has already identified. The importance of widespread notification, testing, and vaccination can also be discussed with the point of contact. Rosters of employees, guests, patrons, or congregants can be collected so the outbreak team can assist in widespread and anonymous notifications of possible exposures and recommendations for testing. Guidance for making these notifications and starting investigations is given in Working with COVID-19 exposures in public or crowded locations. Should the point of contact prefer to do these notifications internally, the lead outbreak investigator can provide the necessary information for them to do so, examples provided in Widespread notification following COVID-19 exposures
  • Widespread Notification: Notification to individuals extending farther than the close contact definition is critical in stopping the spread of COVID-19. Close contacts are those individuals at highest risk for contracting COVID-19, but frequently exposures occur over extended periods of time or involve high-exertion activities with heavy breathing that can increase the risk of transmission of COVID-19, despite those individuals not being strictly considered a ‘close contact’. Ensuring there is a system in place to notify these casual contacts is another critical piece to outbreak response. Widespread notifications are important in both high and low transmission settings. This may change from setting to setting. For example, it may involve notifying all employees at a workplace, all churchgoers, notices at a gym, patrons at a restaurant, etc.
  • Cluster Mapping: Mapping chains of transmission and outbreak events often highlight transmission dynamics to the lead investigator and help to visualize where preventive measures may have broken down. Maps can be simple, but are invaluable tools to help share the lessons learned with community partners and local or state government officials who may not be as closely involved in COVID-19 transmission dynamics as public health officials are. Cluster maps are valuable in both high and low transmission settings. For example templates for cluster maps see here. Examples and instructions on cluster mapping can be found in How to make a case map for outbreak investigations

If a high percentage of cases can be thoroughly and completely interviewed by available staff, workflow modifications can include:

  • Individual Case-Linkages: In areas with low levels of community transmission, mega-clusters may not be as frequently identified, but COVID-19 always comes from somewhere. Cases are either imported into or spread within a community. Strategies should be developed to look at COVID-19 case demographic and geographic data to identify hidden linkages between cases. This strategy should be coupled with widespread testing and vaccination campaigns to protect these social groups and geographical areas from outbreaks in the event of an increase of COVID-19 community transmission.

Additionally, some elements can be added to these core workflows as resources allow and when needed based on the types of transmission that are most common in the area:

  • Community Outreach: Increases in transmission can be anticipated ahead of social events, holidays, and religious celebrations. Sector-specific community outreach is an effective tool for increasing messaging and education related to preventive measures. For example, if a church leader were inclined to send a COVID-19 prevention message to their congregation ahead of a large religious holiday, their community is likely to heed their advice much more seriously than a public health official. Every opportunity to engage community leaders and leverage their channels of communication should be used to mitigate outbreak events, in both high and low transmission settings
  • Super-Spreading Event Response: COVID-19 is a clustering disease, and in areas with high levels of community transmission, larger outbreaks are common in workplaces and public-facing locations. Quick identification of these outbreaks is crucial, as workplaces and public-facing locations act as amplifiers for COVID-19 transmission, creating an opportunity for extensive household and community spread. Strategies should be developed to quickly identify these mega-clusters, coupled with swift sector-specific mitigation techniques and widespread exposure notifications. Testing and vaccination should be encouraged for staff and any community member associated with the outbreak location.

Adapting to the Evolving EpidemicCopy Link!

Updated: October, 2021

A core element of effective outbreak response is to remain dynamic and flexible, and to use the information that is being gathered in ongoing outbreaks to better discover and respond to future outbreaks. Some elements of this include:

  • Shifting trends: Outbreak response teams will quickly develop a sixth-sense for changes in disease transmission, severity, and affected populations. These shifts in COVID-19 trends should be monitored and reported to local and state public health authorities, and prioritization adjusted to accommodate as necessary. For example, shifts may occur in age patterns, types of exposure settings, vaccine breakthroughs, geography of outbreaks, etc.
  • Prioritization: As transmission dynamics shift, prioritization should also shift to ensure outbreak response is being targeted to the highest-risk populations. These priorities could be demographic, geographic, or sector-specific.
  • Surges: Numerous outbreaks are occurring during COVID-19 surges when community transmission is at its highest, but the types and size of outbreaks shift with transmission levels. Outbreak response teams should be dynamic and able to identify high priority outbreaks, defined by extent or risk for poor clinical outcome. These outbreaks should have resources made available as fast as possible for widespread testing and vaccination.

Best Practices for HiringCopy Link!

Updated: October, 2021

  • Diverse workforce: Outbreaks occur in high-risk groups; these groups tend to be demographically or geographically similar. A workforce that is made up of all socio-economic and demographic backgrounds will help to understand the cultural and societal contexts of outbreaks. Language skills can be critical for tracing and outbreak response; hiring a team who speak the main languages in the community is necessary.
  • Varied backgrounds: Knowledge of public health systems and disease control measures are beneficial in outbreak response programs, but are not the sole areas of expertise valuable to the response. Many other skillsets, such as communication, public relations, health education, and a variety of employment backgrounds are beneficial to outbreak investigation and response as these outbreaks are not restricted to typical public health environments. The ability to communicate and build trusting relationships with community members, businesses, and health departments is often a skill that can’t be easily taught, and is incredibly valuable in relationship building and mitigating transmission.

TrainingCopy Link!

Updated: October, 2021

Tool: Training on ‘Introduction to COVID-19 Source Investigation & Clusters’

In ideal circumstances, a specialized outbreak response team can be from the existing contact tracing workforce, but this may vary depending on the context. Outbreak specialists and specialized case investigators should have a basic understanding of case investigation and contact tracing. While not necessary, a moderate understanding of epidemiological and clinical principles is helpful for a fast-paced and quickly evolving outbreak response team.

Extensive academic backgrounds or first-hand knowledge of epidemiology beyond contact tracing experience is not required for most roles in the outbreak response team, however a leadership team that is able to guide new team members through necessary concepts is beneficial to the growth of the team.

Once the team has received the baseline COVID-19 contact tracing training modules (advanced case investigation, source investigation, retrospective contact tracing, basic COVID-19 epidemiology, introduction to clusters, methods for location outreach, etc.; view Training on ‘Introduction to COVID-19 source investigation & clusters for examples of training modules); strategic development should be ongoing for both the outbreak specialists and specialized case investigators, as disease and transmission dynamics evolve frequently, and should include:

  • Trend assessment (geographical, sector-specific, demographic, etc.)
  • Development of sector-specific strategies for communicating with businesses and other public locations
  • COVID-19 guidelines as they evolve for tracing, testing, and vaccination

Training for the outbreak response team should be seen as constantly ongoing. While formal initial trainings can be helpful to get the team started, informal and conversational seminars can be more effective in facilitating ongoing training and understanding.

Metrics and MonitoringCopy Link!

Updated: October, 2021

Outbreak response metrics and evaluation should be conducted in tandem with evaluation of the standard contact tracing system in place. Much of the work of the outbreak response team will be dependent on the quality and availability of data collected through normal contact tracing. In particular, exposure sources and employer information are critical foundations of an outbreak response team.

Much like building the outbreak investigation team and outbreak investigation itself, monitoring of the program should be flexible and adapt to what is possible with the current team. Metrics and outcomes can range from simple (eg. number of clusters created, number of cases associated) to more complex (eg. percent of transmission explained, average cluster attack rates and vaccine effectiveness).

Examples of metrics:

  • Number of clusters created in a time period
  • Number of clusters per transmission sector
  • Number of cases and contacts associated with clustersPercent of contacts and casual contacts reached during cluster investigation
  • Numbers of people connected to testing, vaccination, and other social support services

Examples of exploratory data analysis to identify trends, confirm or readdress priorities, and identify gaps:

  • Proportion of an age group’s cases that are connected to clusters
  • Proportion of cases reporting a given primary language that are connected to clusters
  • Vaccination status of cluster identified and all cases identified
  • Attack rates and total sizes of clusters per sector and over time

Digital and Technology SolutionsCopy Link!

Updated: October, 2021

Tool: Proposed Data Queries to Assist in Outbreak Investigations (provides a list of standard data queries that can be useful in cluster detection and identification)

Sophisticated tools like algorithmic cluster detection and text-based data mining can be helpful in cluster detection, but they should not form the basis of investigation. Standard methods of manual data review by outbreak specialists and case investigators, as well as clear communication across the teams and high-quality data collection, are a much more important starting point.

One of the key tools to detecting clusters is a data system that allows all users to both record key individual-level information related to clusters (e.g. source investigation results) and to ‘flag’ cases that are potentially part of cluster events. This can be done with the use of specific variables in the data system, or through external methods such as spreadsheets to track potential cluster leads. This allows cases of interest to be reviewed by the outbreak team, without requiring all contact tracing staff to be fully trained on investigation techniques.

Another key tool is the ability to generate data queries or perform complex searches in your data system. At minimum, Outbreak Specialists should be able to generate data queries to view the demographics (date of birth, language, city of residence, gender), basic clinical information (vaccination status, presence of symptoms and symptom onset date), and contact tracing data (exposure source, household connections, employer name/address). Further, the ability to perform keyword searches through these fields for all cases is required (ex. searching for all cases in the data query among a given employer name).

Systems StrengtheningCopy Link!

Updated: October, 2021

A fully integrated and comprehensive outbreak response team helps to target resources (human, time, and material) to populations that are the most vulnerable to COVID-19. Whether by geographic or demographic characteristic, or shared social beliefs on COVID-19 and/or vaccination, COVID-19 identifies individuals and locations that need the resources the most.

People are often more willing to discuss testing and vaccination following an exposure or outbreak to COVID-19, despite their previous hesitancies. Flooding these populations with individualized education campaigns, testing and vaccination resources, and care resource coordination ensures the highest risk individuals get the support they need to isolate and quarantine safely, but also to access reliable resources to seek testing and vaccination. Improving vaccination in these populations prevents severe disease and future outbreaks, lessening the burden on the healthcare infrastructure and allowing Local Health Departments to prioritize other public health interventions in addition to COVID-19 response. Those who become convinced to get tested and vaccinated through an outbreak response can also in turn be trained to become vaccination ambassadors for their family, friends, wider social networks, and communities.