COVID-19 Guidance for Isolation, Quarantine and Transmission-Based Precautions - August 2022

Updated Summary of Current City of St. Louis Department of Health COVID-19 Guidance for Isolation, Quarantine and Transmission-Based Precautions


The City of St. Louis Department of Health recommends guidance based on the science provided by the Centers for Disease Control and Prevention (CDC) and local epidemiology.

  • With rare exceptions described below, people who test positive for COVID-19 and recover should not be retested until more than 90 days (3 months) after the date they test positive; they do not need to quarantine for the three months (90 days) following the date of their positive test result per the City of St. Louis Department of Health (CSTLDOH) guidance. This applies even if they have a new exposure to COVID-19. 
  • A negative PCR test should not be required before someone with confirmed COVID-19 returns to work. This is because viral RNA may be detected for several weeks or months after someone is no longer infectious.
  • Health care personnel (HCP) should notify their employer if they are diagnosed with COVID-19, have symptoms consistent with COVID-19, or have an exposure to a person diagnosed with COVID-19. HCP must adhere to their employer’s guidance, which may be more conservative than that of CDC or CSTLDOH. Guidance for health care workers is not included in this guideline. Please refer to the CDC’s policy page for HCP
  • For more information on symptoms, visit the CDC’s COVID-19 symptoms webpage.
  • For information on available therapeutics, visit the CSTLDOH Treatments webpage.
  • Proper selection and proper wearing of face masks remains a critical component of risk mitigation.  Please see below for guidance.


  • Isolation is the separation of people who have a contagious disease to prevent them from transmitting it to others.
  • Exposure is close proximity to a person with a contagious disease for a period of time long enough to become infected.
  • Transmission-based precautions are to be used in addition to standard precautions for patients who may be infected with SARS-CoV-2 or other agents for which additional precautions are needed. For complete infection control guidance for COVID-19, please refer to the CDC’s Infection Control Guidance webpage.
  • Diagnostic tests include any SARS-CoV-2 Nucleic acid amplification-based testing such as a PCR test or antigen test, including at-home diagnostic tests. For more information on at-home tests, visit the CDC webpage on self-testing. Note that at-home test results may not be accepted for some purposes, such as school, employer or travel testing requirements, and are not appropriate for use in hospitalized patients. Diagnostic tests do not include antibody tests.
  • When to begin counting for exposure or isolation: 
    • Exposure: The date of your last exposure to someone with COVID-19 is considered day 0. Day 1 is the first full day after your last contact with a person who has had COVID-19.
    • Isolation: Day 0 is your first day of symptoms or a positive viral test. Day 1 is the first full day after your symptoms developed or your test specimen was collected.

Masks: Materials and Wearing

The CDC advises wearing face masks or respirators for all individuals who are able to appropriately do so. CSTLDOH recommends that everyone properly wear a face mask when in public spaces and when they will be in the company of anyone who does not live in their household. When worn properly, face masks primarily contain exhaled respiratory droplets and particles, while providing some protection against inhaling materials exhaled by others. Respirators protect against inhalation of particles as well as containing exhaled respiratory droplets and particles.

KN95 respirators

Designed to meet international safety standards.

  • Difficult to wear with facial hair
  • Cannot be washed
  • Many sold in the US are counterfeit and do not meet standards – check here before purchasing 

N95, N99, N100, P95, P99, P100, R95, R99, and R100 respirators

Approved by National Institute for Occupational Safety and Health (NIOSH).

Workplace Performance Masks and Workplace Performance Plus Masks

Meets NIOSH performance criteria for workplace safety.

Cloth mask covering a medical procedure mask OR medical procedure mask with a fitter or brace

A fitted cloth mask worn over a medical procedure mask greatly reduces transmission of particles.

  • Medical procedure masks are single-use
  • Cloth masks must fit snugly to the cheeks – see here for additional criteria

Double-layered cloth mask with filter OR medical procedure mask

A 3-ply cloth mask or a medical procedure mask will reduce transmission of particles.

  • Cloth masks are reusable
  • While this option still provides protection, care must be taken to keep masks free of contaminants


Overview of Isolation and Transmission-Based Precautions 

If a person has a positive diagnostic test for OR symptoms of COVID-19

Health care providers should consult their Infection Control Coordinator.

People who are severely immunocompromised should see below.

  • Symptomatic individuals regardless of vaccination status, Isolate at home, and get tested for COVID-19
  • Individuals can discontinue isolation after 5 days IF fever-free for 24 hours without medication, OR after day 10 AND symptoms are resolved if:
    • An antigen test taken on day 5 is positive
    • The illness experienced is moderate or severe
  • Individuals must also continue to properly wear a well-fitting mask around others for 10 days after the start of symptoms, or after receiving a positive test.

Severely immunocompromised people in any setting*

  • Individuals should speak with their medical provider(s) to determine if they are identified as severely immunocompromised
  • Isolation, or transmission-based precautions for those receiving medical care.
  • Individuals can discontinue isolation at the discretion of their healthcare provider.

* CDC defines severely immunocompromised as certain conditions, including being on chemotherapy for cancer, untreated HIV with CD4 count of less than 200, combined primary immunodeficiency disorder, and receipt of prednisone of more than 20 milligrams per day for more than 14 days, that may cause a higher degree of immunosuppression and therefore require different isolation considerations.  Per CSTLDOH guidance, severely immunocompromised patients who were asymptomatic at the time of their first positive test and subsequently developed symptoms attributed to COVID-19 must isolate for at least 5 days and up to 20 days after symptom onset at the discretion of their healthcare provider. 

If a person has a exposure to a positive COVID-19 individual

Exposure within their household:

The CDC recommends improving ventilation and taking other safety precautions in households with children under 2 years of age, or with other family members who cannot wear a mask.

  • The Department of Health recommends that individuals who cannot wear a mask appropriately should quarantine for ten (10) days.

No quarantine is needed if family members can:

  • Distance from the ill family member and 
  • Wear a well-fitting mask around others for 10 days from the last date of exposure

Individuals exposed should get tested at least 5 full days after the last exposure and avoid places where they are unable to wear a mask, including travel and public transportation settings.

Exposure outside of the household:

The individual should wear a well-fitting mask around others for 10 days from the last date of exposure. They should also: 

  • Get tested at least 5 full days after the last exposure
  • Do not go places where you are unable to wear a mask, including travel and public transportation settings

You can still develop COVID-19 up to 10 days after you have been exposed.

The City of St. Louis Department of Health may change recommendations as the situation evolves.

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