Infection Prevention and Control

Transmission PreventionCopy Link!

This section addresses transmission prevention. Please see COVID overview for the causes of Infectivity and Transmission.

Literature Review (Infection Control): Gallery View, Grid View

Wearing Face Masks and ShieldsCopy Link!

Updated Date: December 19, 2020
Literature Review:
Gallery View, Grid View

This section covers general public use of face masks and shields, for health care usage, see Personal Protective Equipment

Universal masking has been shown to reduce transmission. More data exist for medical settings, but the United States CDC and the WHO both recommend mask use in non-medical settings as well (CDC, WHO).

How do Face Masks Work?Copy Link!

  1. Face Masks provide a barrier against a high percentage of the viral particles released from a wearer’s mouth and nose (Ma et al).
  1. Wearing a medical mask has been demonstrated to result in a six-fold decrease in particle emission during breathing (Asadi et al). Systematic review of research literature on face masks shows that they reduce risk of infection by 85%, with greater effect noted in healthcare settings (MacIntyre et al). Even loose-fitting masks appear to block 51% of particles. (Brooks et al)
  1. Available evidence also indicates that face masks can protect the wearer from inhaling viral particles. Face masks with multiple layers of cloth containing higher thread counts are more effective (CDC).
  2. The effectiveness of masks may be different as new more transmissible viral variants with higher viral loads, such as Delta variant, emerge (Hetemaki et al). However, they are likely to retain some efficacy.
  3. Populations can more easily adhere to universal masking advice than stay-at-home orders in some settings. Face masks allow people to leave their homes for essential reasons with less risk to others.

Can Face Masks Harm People?Copy Link!

Face masks do not interfere with the exchange of oxygen or carbon dioxide, even in patients with severe lung impairment (Samannan et al). Depending on the face mask, it may change the rate of flow of air, which can make people feel uncomfortable, especially if they have obstructive lung disease that also impedes air flow, such as COPD or asthma. Wearing a medical mask can be uncomfortable, but will not cause oxygen deficiency or carbon dioxide intoxication. Make sure that face masks remain dry (WHO). CDC recommends face masks above age 2; WHO recommends against requiring face masks for children under the age of 5 (WHO).

Types of Face MaskCopy Link!

There are several major categories of face masks. In many places manufactured medical-grade face masks (surgical, KN95, and 95) are in short supply. If there is a shortage of medical-grade face masks, they should be reserved for healthcare workers, confirmed COVID-19 patients, patients with symptoms of COVID-19, or patients at high risk of complications (WHO). More details on different types of medical-grade masks are available in PPE Types and Uses.

Tool: Instructions on How to Make Your Own Face Mask.

Face Shields and GogglesCopy Link!

Face shields and goggles are meant to prevent droplets and sprays from entering the eyes (for example, when caring for a hospital patient or a sick family member at home).Regulatory guidance and standards on forms of eye protection are highly variable. For best protection, wear a face shield that fits snugly against the forehead and extends the full length of the face and to the point of each ear (Roberge).. There is lack of evidence to demonstrate that face shields alone are sufficient as a form of source control for protecting others (CDC). They are also not sufficient to protect the wearer when worn alone, and should generally be worn with a face mask (Roberge). When a face mask cannot be worn, a face shield can be worn instead but does not offer the same level of infection control (CDC).

When to Wear a Face MaskCopy Link!

  1. When leaving the house
  2. In quarantine/self-quarantine/isolation when contact with others is necessary
  3. In workplaces and on public transportation
  4. When entering someone else’s home to provide an essential service
  5. When indoors with people who do not belong to your household, including relatives
  6. When cleaning streets or disposing of domestic rubbish
  7. A face mask is suggested, but not absolutely necessary in some outdoor areas if a 2-meter distance can be kept from other people at all times. Consult local rules and regulations.

How to Use a Face MaskCopy Link!

  1. Wash your hands with soap and water or an alcohol-based hand sanitizer before putting on, touching, or removing a face mask (WHO). This prevents you from accidentally contaminating your face if you have coronavirus on your hands. Avoid touching the front of a face mask by touching the strings or ties instead.
  2. The face mask must be worn over both the mouth and the nose, it is not effective if used over the mouth alone. Tie securely to minimize gaps between face and mask.
  3. Avoid touching the face mask while wearing it. If you do, perform hand hygiene.
  4. When removing a face mask, undo the ties and carefully fold the face mask inside-out. Place directly in a designated area for disposal or washing, or in a plastic bag.
  5. Wash cloth face mask in soap or detergent, preferably with hot water. If hot water cannot be used, boil the mask for 1 minute after washing with detergent (WHO). Only use a cloth face mask that has been properly cleaned.
  6. If a face mask becomes damp or noticeably soiled, replace it immediately with a clean one.

Tool: WHO Infographics on How to Wear a Face Mask

Policy Interventions Around Face Mask UseCopy Link!

Adapted in large part from the South African Recommendations:

  1. Public health leaders should create media campaigns to educate the public on the use of face masks, including how to safely use them.
  2. In COVID-19 hotspots it is reasonable for policy makers to make face masks mandatory, especially in spaces where physical distancing is challenging. Educational campaigns should be prioritized over punitive measures to promote adherence.
  3. Face masks are not a substitute for other preventive measures like regular handwashing, cleaning surfaces, physical distancing and contact tracing. All must be done together whenever possible.

Physical DistancingCopy Link!

Updated Date: December 19, 2020
Literature Review:
Gallery View, Grid View

Physical DistancingCopy Link!

The World Health Organization recommends people maintain a physical distance of 1 meter between them. This is based on research on bacterial meningitis and rhinovirus spread (WHO)

In contrast the United States Centers for Disease Control (CDC) recommend a distance of 2 meters. This recommendation is based on measurements of influenza transmission, sometimes from studies in the 1930-40s (Wells).

There is no known distance cutoff that absolutely protects a person from being exposed to any droplets or aerosolized particles (see Aerosols, Droplets, and Fomites). Sneezing and coughing can create turbulent gas clouds that can spread droplets well past a distance of 2 meters (Bourouiba). However, the density of droplets seems to decline the farther away from another person you stand.

Outdoor TransmissionCopy Link!

Transmission is less likely outdoors and in other well-ventilated spaces. Systematic review of evidence indicates that COVID transmission is significantly reduced outdoors: outdoor transmission is responsible for <10 % of reported transmissions globally (Bulfone et al). In indoor spaces, low ventilation and lack of ventilation are both associated with higher transmission rates of airborne diseases (WHO). In one study of transmission in China, only one case among 7300 was associated with outdoor transmission (Qian). However, with more infectious variants such as the Delta variant there are reports of outdoor transmissions at music festivals in the USA and playgrounds in Australia, especially with shoulder-to-shoulder events. However, it is still far less likely than indoors.

Surface DecontaminationCopy Link!

Updated Date: December 19, 2020
Literature Review (Fomites):
Gallery View, Grid View

Surface decontamination can help prevent the spread of COVID-19, though transmission through transmission from surfaces and fomites is not common (see Aerosols, Droplets, and Fomites). Particular attention should be paid to cleaning high touch surfaces frequently. Instructions for making cleaning products and example cleaning schedules are found in Disinfection and Cleaning.

Hand HygieneCopy Link!

Updated Date: December 19, 2020

Effective hand washing is a proven way to remove bacteria and viruses from hands and prevent illness. The exact contribution hand washing has made to population health during the COVID pandemic is currently unknown (CDC), but it is presumed to reduce COVID transmission. Hand washing should be performed with soap and water for at least 20 seconds. Alcohol solutions with at least 70% alcohol can also be used.

When around someone with known COVID-19 infection, hand washing is always a critical protection for staff, patients, and families. Gloves should be used for all blood and body fluids.

The WHO recommends handwashing at five times:

  1. Before touching a patient
  2. Before clean/aseptic procedures
  3. After touching a patient
  4. After body fluid exposure
  5. After touching a patient’s surroundings

Exposures, Isolation and QuarantineCopy Link!

Exposure to COVIDCopy Link!

Updated Date: December 19, 2020
Literature Review:
Gallery View, Grid View

If a patient believes they have been exposed to COVID-19 it is important to assess risk in order minimize anxiety of lower-risk exposures and identify higher-risk exposures and prevent further transmission.

Definition of COVID ExposureCopy Link!

An exposure is defined differently by different groups. Some general guidance is being within 1 meter (WHO) or 2 meters (CDC) feet of an infectious COVID positive person for greater than 15 minutes or direct physical contact without PPE. It should be noted that there is no evidence for a minimum amount of time that it takes when exposed to become infected.

  • A person is considered infectious:
  • If Symptomatic: from 2 days before symptom onset until 14 days after (WHO) or until meeting criteria for discontinuing isolation (CDC) (see Releasing Patients from Isolation).
  • If Asymptomatic: from 2 days before the date of positive test until meeting criteria for discontinuing isolation.

Risk of Developing Disease After ExposedCopy Link!

Risk depends considerably on the duration and proximity of the exposure and how symptomatic the original patient was. Using a similar exposure definition to the CDC definition, investigators found 13% of exposed individuals subsequently developed COVID-19 (Boulware et al). This is higher amongst household contacts (see Household Transmission).

Prophylaxis: At this time, there are no known effective pre- or post-exposure prophylaxis for COVID-19. A large trial of hydroxychloroquine as post-exposure prophylaxis demonstrated no benefit and increased risk of self-reported adverse events in the treatment arm (Boulware et al).

Testing after ExposureCopy Link!

Please see Testing Asymptomatic Patients

Quarantine and IsolationCopy Link!

Updated Date: April 23, 2021

IsolationCopy Link!

Isolation is the separation of a sick person with a contagious disease from people who are not sick. We recommend isolation for all suspected, presumptive and confirmed cases of COVID-19. Duration of isolation depends on many different factors, and this is covered in Releasing Patients from Isolation. (CDC guidelines). Facility based isolation of COVID-19 cases is discussed in Transmission Prevention in Facilities.

QuarantineCopy Link!

Quarantine is the separation of people who were exposed to a contagious disease to see if they become sick. We recommend quarantine of all persons that have been exposed to COVID-19 cases.

  • Duration of quarantine is typically 14 days from last exposure.
  • December 2, 2020 CDC guidance states quarantine can be reduced in certain circumstances. Keep in mind this may not apply everywhere, and local authorities may have longer or shorter guidelines as they consider changing evidence and resources. As the CDC states:
  • Quarantine can end after Day 10 without testing and if no symptoms have been reported during daily monitoring. With this strategy, residual post-quarantine transmission risk is estimated to be about 1% with an upper limit of about 10%.
  • Quarantine can end after Day 7 if a diagnostic specimen (collected within 48h of Day 7) tests negative and if no symptoms were reported during daily monitoring. With this strategy, the residual post-quarantine transmission risk is estimated to be about 5% with an upper limit of about 12%.
  • Please note: for COVID vaccinated patients defined as individuals two week out from final dose of COVID vaccine, the CDC states individuals may refrain from a full quarantine if they do not have symptoms of COVID-19 after contact with someone who has COVID-19. They do recommend fully vaccinated people should get tested 3-5 days after their exposure, even if they don’t have symptoms and wear a mask indoors in public for 14 days following exposure or until their test result is negative. We expect that this may change given the emergence of variants. This is liable to be different in different epidemiologic contexts, and consulting your local public health regulations is advised.

IPC for Home Quarantine or IsolationCopy Link!

Requirements for Isolation and Quarantine

Physical Distance

  • Accept no visitors from outside the home
  • Maintain a distance of >1 meter from other household members, with only one person assigned to be the caregiver to the patient (this should not be anyone at high risk of severe COVID disease.)
  • Keep patient in a well-ventilated single room, ideally on a separate floor If a fan is available, point it out of one window and keep another window open to facilitate increased air exchange.
  • Have the patient use a separate bathroom if possible; if not clean the bathroom after use
  • No visitors should come to the home during the 14 days.
  • If patient is a primary caregiver to another household member, assign someone else to take over those responsibilities
  • Know When to Seek Care


  • Patients and caregivers should wear masks when not physically separated. Ideally, surgical masks would be used, but cloth masks are an alternative if surgical masks are not available.
  • Caregivers should wash hands after any type of contact with the patient, before and after preparing food, and before eating.
  • All should cover their mouths when coughing or sneezing.
  • Use dedicated eating utensils for the patient. Utensils should be cleaned with soap and water
  • Use dedicated linens for the patient. Linens should be cleaned with hot water and detergent
  • Surfaces should be cleaned with soap, and high-touch” surfaces (e.g. doorknobs) with a household disinfectant daily. Can use a bleach solution (1 part 5% pure bleach diluted with 9 parts water to make a 0.5% solution.)

Releasing Patients from IsolationCopy Link!

Updated Date: December 19, 2020
Literature Review (Clearance and Return to Work):
Gallery View, Grid View

Knowing when a patient has recovered from COVID infection and is no longer infectious is important to allowing them to return to contact with other individuals, including work, school, and living environments.

Time based vs testing based criteria: Most situations call for time-based criteria, because the interpretation of positive tests after infection is complicated (PCR often remains positive even in people who are no longer infectious, see Infectivity.) A test-based strategy can be used for selected recovered persons for whom there is low tolerance for virus shedding and infectious risk (for example, working in healthcare facilities, residing in congregate living facilities, immunocompromised, etc). Some institutions require more stringent clearance criteria than those outlined here.

Tool: CDC When Can You Be Around Others When You’ve Had COVID-19

Tool: WHO Criteria for Releasing from Isolation
Tool: Massachusetts General Brigham Case Clearance

  1. Symptomatic patients (CDC, WHO):
  1. Time-based criteria: 10 days have passed since symptom onset
  2. 24 hours have passed since last fever without use of fever reducing medications (whichever is longer)
  3. Other COVID symptoms are improving (Note: Loss of taste and smell may persist for weeks or months after recovery and need not delay the end of isolation​)
  1. Asymptomatic patients
  1. Time-based criteria: 10 days after positive test (CDC, WHO)
  1. Patients with severe illness or patients with prolonged symptoms:
  1. Time-based criteria: The CDC recommends up to 20 days from symptom onset. WHO makes no distinction based on severity when determining duration of isolation for symptomatic patients.
  1. Currently hospitalized patients:
  1. Time based criteria: This is not universally defined. BWH uses 20 days since first positive test + 1 day after fever and symptom resolution
  2. Test based criteria: This is not universally defined. BWH uses 1 day after symptom resolution + at least 2 negative PCR swabs at least 24 hours apart
  1. Severely immunocompromised patients: Defined by the CDC as patients on chemotherapy for cancer, untreated HIV infection with CD4 T lymphocyte count < 200, combined primary immunodeficiency disorder, and receipt of prednisone >20mg/day for more than 14 days
  1. Time based criteria: 20 days after symptom onset (+ 1 days after symptom resolution). Exact determination of isolation duration in immunocompromised patients should be made in consultation with an Infectious Disease specialist (CDC)

Transmission Prevention in FacilitiesCopy Link!

Updated Date: December 20, 2020

In health care facilities, IPC is critical to reducing the spread of COVID-19.

Screening and movement: Screen all people (staff, patients, and visitors) entering clinical spaces using Screening Questions. Make modifications to patient flow to ensure patients with symptoms of or at risk for COVID-19 are appropriately classified by likelihood of disease, transported safely, and isolated in designated locations.

Physical distancing: Modify waiting and treatment areas to allow physical distancing.

  • Distances between people should be at least 1 meter (WHO recommendation), and ideally 2 meters (CDC recommendation) in all contexts.
  • Avoid gatherings of staff in confined spaces. For example, consider outdoor staff meetings or use technology to hold remote meetings. Rotate meal times to avoid crowds in dining areas and rearrange break areas to allow physical distancing so staff can eat and drink safely. Add additional work spaces to avoid congregating at nursing stations.
  • In spaces where COVID-related care is provided, the number of people (staff, patients, and visitors) should be kept to the minimum needed. Whenever possible, avoid large groupings of people.

PPE: Use appropriate Personal Protective Equipment and train staff on its use

  • Universal Masking in healthcare spaces is always necessary. Medical-grade masks should be used whenever available.
  • Wards and rooms should be clearly marked with appropriate and standardized signage indicating the category of precaution and PPE that is required to enter.

Isolation: Use appropriate facilities and protocols to isolate patients (see isolation). Positive COVID patients, PUIs, and patients without COVID symptoms should not be cohorted together. Ideally, patients should be separated as quickly as possible into separate spaces based on at least three categories (screening negative for possible COVID infection, screening low-likelihood for COVID infection, and screening high-likelihood for COVID infection). Some settings may use as many as five cohorting categories. See Likelihood Categories (Case Definitions), and Isolation.

Ventilation: Using outdoor spaces and spaces with good filtration or air turnover can decrease risk. All indoor spaces should be sufficiently ventilated and COVID care areas should be negative pressure whenever possible (see Ventilation and Filtration).

Decontamination: Clean all contact surfaces between patients for areas with frequent patient turnover (e.g. clinic rooms and triage areas) and equipment that is rotated between patients (e.g. vital sign monitors). Facilities should develop cleaning protocols for all patient and non-patient care areas.

IsolationCopy Link!

Updated Date: December 19, 2020

Isolation in Hospital Rooms and WardsCopy Link!

Never co-house a patient who screens negative in the same room or ward as confirmed positive COVID patients or PUIs. Confirmed positive patients should only ever be housed with other confirmed positives.

There is no universal set of strategic recommendations for inpatient housing arrangements. Healthcare settings vary greatly in terms of floor plan, layout, equipment, and other resources.These are some principles that can be adapted to local context.

Isolation in RoomsCopy Link!

Which patients need single rooms? In settings where most patients are kept in single or double rooms, confirmed positive COVID cases can be cohorted together in shared rooms. However, PUIs should never be roomed together, as this may result in COVID transmission from one roommate to another if one PUI is actually COVID-negative.

Requirements for rooms: The ideal room is a single private negative pressure room with transparent windows, doors that close, and continuous wireless pulse oximetry monitoring. This arrangement is often unavailable outside of critical care settings, even in the world’s best-resourced practice settings. If a room does not have adequate space and monitoring (direct patient visualization, pulse oximetry, and/or telemetry), rooming and location must balance patient safety risks and infection control needs.

Isolation in Wards and Common AreasCopy Link!

COVID-care wards should be as separated as possible (ideally in a different building) from care areas for patients who screen negative for possible COVID infection.

Separating wards by likelihood level: If single isolated rooms are not available or feasible we recommend using multiple wards or areas to separate patients by Likelihood of Disease. Wards for suspected or confirmed COVID patients should always be separate from wards for patients who screen negative for COVID symptoms. Providers should always move from low-risk patients to high-risk patients.

Whenever possible, at least three separate COVID-care wards should be established to safely cohort the following categories. For additional details, see Likelihood Categories (Case Definitions).

  1. Lower-risk PUIs, including minimally symptomatic and asymptomatic patients with known exposure.*
  2. Higher-risk PUIs, including symptomatic suspected cases and probable cases). Ideally these groups would be further subdivided into separate wards or areas based on their likelihood of having COVID (for example, separating suspected lower-likelihood cases from suspected and probable cases with a higher likelihood of disease).*
  3. Confirmed positive COVID cases.

*These first two categories require the highest level of IPC to reduce transmission, as patients in these spaces are a mix of positive and negative.

When it is not possible to separate wards by likelihood level: If separate wards for each level are impossible, PUIs patients may be cohorted within the same ward and grouped according to risk level with physical distance or Barriers between each group of patients. Since not all PUIs will have COVID, it is important to adequately distance (1-2m) PUIs from each other, arrange the ward from the least likely to the most likely patients. Strict IPC and PPE practices are imperative, and providers should try to move from low to high risk patients if possible.

PrecautionsCopy Link!

Updated Date: December 19, 2020
Literature Review (Airborne v Droplet):
Gallery View, Grid View
Literature Review (Aerosolization):
Gallery View, Grid View

Precaution Type for COVID-19Copy Link!

WHO guidance recommends standard, contact and droplet precautions when caring for suspected or confirmed COVID-19 patients. If an Aerosol Generating Procedure is being performed airborne precautions are needed (WHO).

  • Some hospitals may create their own definitions and specific policies with slightly more stringent requirements, such as Enhanced Droplet Precautions. Given concerns that coughing and sneezing may themselves cause aerosols, some hospitals may choose to put all patients on airborne precautions

Tool: CDC Guidance on Contact, Droplet and Airborne Precautions (including sample signs)

Tool: Detailed CDC Guidance Defining Different Levels of Precaution

Standard, Contact and Droplet PrecautionsCopy Link!

Standard, Contact, and Droplet precautions (drawing from CDC guidance) in the setting of COVID include the following (adapted from CDC and WHO) guidance:

  1. Use high-quality hand washing
  2. Use adequate PPE to protect against contact with the patient’s environment and droplets suspended in air (PPE is covered extensively here)
  3. Use Respiratory hygiene/ cough etiquette (cover mouths when coughing and sneezing, tissues, no-touch receptacles)
  1. Patients should wear medical masks whenever possible
  1. Use appropriate patient rooming and distancing (see “isolation” above)
  2. Use safe injection practices
  3. Use safe waste management and linen management
  4. Use designated equipment for COVID patients (or wards) and adequately sterilize equipment (stethoscope, blood pressure cuff, pulse oximeter) between each patient (e.g. with ethyl alcohol 70%).
  5. Minimize patient movement and transportation and use appropriate precautions when transport is needed (see transport below) (see “transport”)
  6. Maintain good ventilation
  1. Open doors and windows when possible, though be careful not to ventilate from COVID areas to non-COVID areas.
  1. Whenever possible, healthcare workers should move lower-risk to higher risk patients (from asymptomatic to symptomatic and then to confirmed positive patients).
  2. Some additional guidance on specific procedures, lab transport, etc is available in BWH’s ICU Strict Isolation Manual

Airborne PrecautionsCopy Link!

Use airborne precautions when there is a risk of aerosolized particles. In the hospital setting, this generally means during Aerosol Generating Procedures (AGPs). (The role of aerosols in COVID-19 transmission is discussed in Aerosols, Droplets, and Fomites). Airborne precautions should be used for all patients (not only confirmed CoVID-19 patients and PUI) for AGPs in places with high prevalence, or where testing to rule out infection prior to the procedure is not possible. In addition to gown, gloves, and eye protection, aerosol-resistant respirators (N95 masks) are needed during aerosol-generating procedures and until adequate air turnover has occurred afterward (air turnover depends on your facility, in most BWH rooms this is 47 minutes). Please see Personal Protective Equipment for guidance.

  1. Use negative pressure rooms wherever possible, or in a well - ventilated space if not (see Ventilation and Filtration).
  2. Limit the number of people in the room to the fewest necessary.
  3. There should be no other patients and no visitors present.

Aerosol Generating ProceduresCopy Link!

Updated Date: December 19, 2020
Literature Review (Airborne v Droplet):
Gallery View, Grid View
Literature Review (Aerosolization):
Gallery View, Grid View

Aerosol Generating Procedures (AGPs) must be performed with Airborne Precautions for COVID patients, and most non-COVID patients (see airborne precautions). Not all institutions use the same definition of an aerosol generating procedure. Some potential examples include:

  1. Intubation
  2. Extubation
  3. Bronchoscopy
  4. Sputum induction
  5. Cardiopulmonary resuscitation (CPR) with chest compressions
  6. Open suctioning of tracheostomy or endotracheal tube
  7. Manual ventilation (e.g. manual bag- mask ventilation before intubation)
  8. Nebulization
  9. High flow oxygen therapy and non-invasive positive pressure ventilation (e.g., CPAP, BIPAP) (though this is not universal in different institutions, and it is not clear if this increases aerosols beyond coughing, see HFNC)
  10. Oscillatory ventilation
  11. Disconnecting patient from ventilator
  12. Upper airway procedures / surgeries
  13. Upper endoscopy (including transesophageal echocardiogram) and lower endoscopy
  14. Chest physical therapy
  15. Autopsy
  16. Thoracentesis/small-bore (pigtail) chest tube placement (due to the increased risk of cough)
  17. Airway surgeries
  18. Tracheostomy changes
  19. Disconnecting patients from ventilator