Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
To maximize protection from the Delta variant and prevent possibly spreading it to others, get vaccinated as soon as you can and wear a mask indoors in public if you are in an area of substantial or high transmission.
UPDATE
Given new evidence on the B.1.617.2 (Delta) variant, CDC has updated the guidance for fully vaccinated people. CDC recommends universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. Children should return to full-time in-person learning in the fall with layered prevention strategies in place.
UPDATE
The White House announced that vaccines will be required for international travelers coming into the United States, with an effective date of November 8, 2021. For purposes of entry into the United States, vaccines accepted will include FDA approved or authorized and WHO Emergency Use Listing vaccines. More information is available here.
UPDATE
Travel requirements to enter the United States are changing, starting November 8, 2021. More information is available here.

Interim Guidance for SARS-CoV-2 Testing in Homeless Shelters and Encampments

Interim Guidance for SARS-CoV-2 Testing in Homeless Shelters and Encampments

Summary of Recent Changes

Key points
  • Testing for Severe Acute Respiratory Coronavirus-2 (SARS-CoV-2) is an important outbreak prevention measure in homeless shelters and encampments.
  • Diagnostic testing, including close contacts of known COVID-19 cases, and screening testing are important in combination to stop the spread of COVD-19.
  • Testing considerations specific to homeless shelters and encampments include, for example, supportive services when isolation is required for persons experiencing homelessness.
  • The level of community transmission can inform testing approaches in homeless shelters and encampments.

Note: This document is intended to provide considerations on the appropriate use of testing and does not dictate the determination of payment decisions or insurance coverage of such testing, except as may be otherwise referenced (or prescribed) by another entity or federal or state agency. CDC is a non-regulatory agency; therefore, the information in this document is meant to assist health departments and homeless service providers in making decisions rather than establishing regulatory requirements. This guidance does not replace any applicable federal, state, Tribal, local, or territorial health and safety laws, rules, and regulations. This guidance has been developed based on what is currently known about SARS-CoV-2 infection and COVID-19 and is subject to change as additional information becomes available.

Introduction

This document describes SARS-CoV-2 testing strategies for homeless shelters and encampments. Many persons experiencing homelessness are older adults and people with underlying medical conditions that put them at higher risk for severe COVID-19 illness. Testing should be used in conjunction with other COVID-19 prevention strategies by homeless service provider sites. Testing results should not be a barrier to accessing homeless services. SARS-CoV-2 testing should not be a pre-requisite for entrance to homeless service sites unless directed by state or local health authorities.

Any time a person tests positive for SARS-CoV-2, ensure that the individual is rapidly and appropriately notified, separated from others, provided appropriate medical care, and linked to appropriate alternative housing for isolation as necessary. Please review guidance for responding to COVID-19 cases at homeless shelters to identify close contacts of the person with the positive test. Testing procedures should protect privacy and confidentiality consistent with applicable laws and regulations. The purpose and process of the testing should be clearly communicated to clients and staff at the homeless service site. To understand the guidance that follows, please review:

Considerations when testing

SARS-CoV-2 testing may be incorporated as part of a comprehensive approach to reducing transmission. Symptom screening, testing, and contact tracing are strategies to identify people infected with SARS-CoV-2 so that actions can be taken to slow and stop the spread of the virus.

COVID-19 vaccine is currently available in limited doses; therefore, CDC’s Advisory Committee on Immunization Practices (ACIP) described recommendations for prioritization during the early phases of the vaccination program. As vaccine supply increases and additional priority groups receive vaccine, CDC’s priorities for SARS-CoV-2 testing will change and the guidance will be updated. For example, as more staff are vaccinated, SARS-CoV-2 testing priorities may shift to focus on unvaccinated staff and residents. For guidance on quarantine and testing of fully vaccinated people, please visit Interim Public Health Recommendations for Fully Vaccinated People.

People undergoing testing should receive clear information on

  • the manufacturer and name of the test, the type of test, the purpose of the test, the performance specifications of the test, any limitations associated with the test, who will pay for the test, how the test will be performed, how and when they will receive test results, and;
  • how to understand what the results mean, actions associated with negative or positive results, the difference between testing for workplace screening versus for medical diagnosis, who will receive the results, how the results may be used, and any consequences for declining to be tested.

Individuals tested are required to receive patient fact sheets as part of the test’s emergency use authorization (EUA)external icon.

Test types

Viral tests

Viral tests authorizedexternal icon by the Food and Drug Administration (FDA) are used to diagnose infection with SARS-CoV-2, the virus that causes COVID-19. Viral tests evaluate whether the virus is present in respiratory or other specimens. Results from these tests help public health officials identify and isolate people who are infected to minimize SARS-CoV-2 transmission. See FDA’s list of In Vitro Diagnostics Emergency Use Authorizationsexternal icon for more information about the performance of specific authorized tests.

  • Nucleic acid amplification tests (NAATs), such as real-time reverse transcription-polymerase chain reaction (RT-PCR), detect viral ribonucleic acid (RNA) and indicate a current infection or a recent infection with prolonged viral RNA detection but without direct evidence for virus capable of replicating or of being transmitted to others. NAATs are high-sensitivity, high-specificity tests for diagnosing SARS-CoV-2 infection. Most NAATs need to be processed in a laboratory with variable time to results (~1–2 days), but some NAATs are point-of-care tests with results available in about 15–45 minutes.
  • Antigen tests detect the presence of a specific viral antigen. Most can be processed at the point of care with results available in about 15–­30 minutes. Antigen tests generally have similar specificity but are less sensitive than NAATs. Depending on the pre-test probability, antigen test results may need confirmation with a NAAT (e.g., a negative test in persons with symptoms or a positive test in persons without symptoms). Use of the Antigen Testing Algorithm pdf icon[147 KB, 1 page] is recommended to determine when confirmatory testing is needed.

Antibody tests

Antibody (or serology) tests are used to detect previous infection with SARS-CoV-2 and can aid in the diagnosis of Multisystem Inflammatory Syndrome in Children (MIS-C) and in adults (MIS-A). CDC does not recommend using antibody testing to diagnose current infection. Depending on the time when someone was infected and the timing of the test, the test might not detect antibodies in someone with a current infection. In addition, it is not currently known whether a positive antibody test result indicates immunity against SARS-CoV-2; therefore, at this time, antibody tests should not be used to determine if an individual is immune against reinfection. Antibody testing is being used for public health surveillance and epidemiologic purposes. Because antibody tests can have different targets on the virus, specific tests might be needed to assess for antibodies originating from past infection versus those from vaccination. For more information about COVID-19 vaccines and antibody test results, refer to Interim Clinical Considerations for Use of mRNA COVID-19 Vaccines Currently Authorized in the United States.

For more information, please refer to Overview of Testing for SARS-CoV-2.

Overview of testing scenarios

Diagnostic testing is intended to identify current infection in individuals and is performed when a person has signs or symptoms consistent with COVID-19, or when a person is asymptomatic but has recent known or suspected exposure to SARS-CoV-2.

Examples of diagnostic testing include:

  • Testing people who have symptoms consistent with COVID-19 and who present to their healthcare provider
  • Testing people as a result of contact tracing efforts
  • Testing people who indicate that they were exposed to someone with a confirmed or suspected case of COVID-19
  • Testing people who attended an event where another attendee was later confirmed to have COVID-19

Screening tests are intended to identify infected people who are asymptomatic and do not have known, suspected, or reported exposure to SARS-CoV-2. Screening helps to identify unknown cases so that measures can be taken to prevent further transmission.

Examples of screening include:

  • Testing employees in a workplace setting
  • Testing students, faculty, and staff in a school or university setting
  • Testing a person before or after travel
  • Testing at home for someone who does not have symptoms associated with COVID-19 and no known exposures to someone with COVID-19

Choosing a test

When choosing which test to use, it is important to understand the purpose of the testing (e.g., diagnostic, screening), analytic performance of the test within the context of the level of community transmission, need for rapid results, and other considerations. Table 1 summarizes some characteristics of NAATs and antigen tests to consider. Most antigen tests that have received EUA from FDAexternal icon are authorized for testing symptomatic persons within the first 5, 7, 12, or 14 days of symptom onset. Given the risk of transmission of SARS-CoV-2 from asymptomatic and presymptomatic persons with SARS-CoV-2 infection, use of antigen tests in asymptomatic and presymptomatic persons can be considered. FDA has provided a list of FAQ for healthcare providers who are using diagnostic tests in screening asymptomatic individualsexternal icon, and the Centers for Medicare & Medicaid Services will temporarily exercise enforcement discretionpdf iconexternal icon to enable the use of antigen tests in asymptomatic individuals for the duration of the COVID-19 public health emergency under the Clinical Laboratory Improvement Amendments of 1988 (CLIA). Laboratories that perform screening or diagnostic testing for SARS-CoV-2 must have a CLIA certificate and meet regulatory requirements. Tests that have received an EUA from FDA for point of care (POC) use can be performed with a CLIA certificate of waiver.

Table 1. NAAT and Antigen Test Differences to Consider When Planning for Diagnostic or Screening Use

NAATs

Antigen Tests

Intended Use

Detect current infection

Detect current infection

Analyte Detected

Viral Ribonucleic Acid (RNA)

Viral Antigens

Specimen Type(s)

Nasal, Nasopharyngeal, Oropharyngeal, Sputum, Saliva

Nasal, Nasopharyngeal

Sensitivity

Varies by test, but generally high for laboratory-based tests and moderate-to-high for POC tests

Varies depending on the course of infection, but generally moderate-to-high at times of peak viral load*

Specificity

High

High

Test Complexity

Varies by test

Relatively easy to use

Authorized for Use at the Point-of-Care

Most are not, some are

Most are, some are not

Turnaround Time

Most 1-3 days. Some could be rapid in 15 minutes

Ranges from 15 minutes to 30 minutes

Cost/Test^

Moderate (~$75-$100/test)

Low (~$5-$50/test)

Advantages

Most sensitive test method available

Short turnaround time for NAAT POC tests, but few available

Usually does not need to be repeated to confirm results

Short turnaround time (approximately 15 minutes)+

When performed at or near POC, allows for rapid identification of infected people, thus preventing further virus transmission in the community, workplace, etc.

Comparable performance to NAATs in symptomatic persons and/or if culturable virus present, when the person is presumed to be infectious

Disadvantages

Longer turnaround time for lab-based tests (1–3 days)

Higher cost per test

A positive NAAT diagnostic test should not be repeated within 90 days, because people may continue to have detectable RNA after risk of transmission has passed

May need confirmatory testing

Less sensitive (more false negative results) compared to NAATs, especially among asymptomatic people

*The decreased sensitivity of antigen tests might be offset if the POC antigen tests are repeated more frequently (i.e., serial testing at least weekly).
^ Costs for: NAATsexternal icon
+Refers to point-of-care antigen tests only.

Considerations for testing in different scenarios

Diagnostic testing

Testing persons with signs or symptoms consistent with COVID-19

Persons experiencing homelessness who have COVID-19 signs and/or symptoms should be escorted to a private area as described in Interim Guidance for Homeless Service Providers. The client should wear a mask covering the nose and mouth and possibly be sent to a healthcare facility, depending on the severity of symptoms. Testing can be performed in accordance with the emergency use authorization to determine if the individual is infected with SARS-CoV-2 by antigen test or NAAT.

Testing asymptomatic persons with known or suspected exposure to SARS-CoV-2

Unvaccinated close contacts of persons with COVID-19 should quarantine and be tested. However tracing close contacts of persons experiencing homelessness can be challenging and location-based contact tracing can be used—that is, broader testing of clients, staff, and volunteers in locations the person with COVID-19 recently visited. Additional considerations include:

Testing to determine resolution of infection

Accumulating evidence supports ending isolation and precautions for persons with COVID-19 using a symptom-based strategy. Adults with more severe illness or who are immunocompromised may remain infectious up to 20 days or longer after symptom onset, so a test-based strategy could be considered in consultation with infectious disease experts for these people. For all others, a test-based strategy is no longer recommended except to discontinue isolation or precautions earlier than would occur under the symptom-based strategy.

Screening testing

Testing asymptomatic persons without known or suspected exposure to SARS-CoV-2 for early identification, isolation, and disease prevention

Widespread testing, regardless of signs or symptoms, is a key component of a layered approach to prevent SARS-CoV-2 transmission in congregate settings. This screening allows early identification and isolation of persons who are asymptomatic, presymptomatic, or have only mild symptoms and who may be unknowingly transmitting virus. In screening settings where antigen tests are used, confirmatory NAAT testing is recommended for individuals who test positive. For interpretation of screening test results, please see the Antigen Test Algorithmpdf icon. Frequency of screening testing can be informed by the level of community transmission (Table 2).

Data on community transmission level can guide decisions about screening testing strategies in homeless shelters and encampments (Table 2). If facility-wide testing is indicated, NAAT or antigen testing can be offered to all clients and staff.

  • Clients with a positive test should be connected to a place where they can isolate safely and access necessary services until they meet criteria to discontinue isolation.
  • Staff with a positive test should seek medical care if needed and to stay home until they meet criteria to discontinue isolation.
  • Continue repeat viral testing of all previously negative or untested clients, staff, and volunteers, generally every 3 days to 7 days, until the testing identifies no new cases of SARS-CoV-2 infection for a period of at least 14 days since the most recent positive result.
  • Given the incubation period for COVID-19 (up to 14 days), CDC recommends conducting screening testing at least weekly.

Homeless service providers can consider adding aggregate testing results in the CDC and National Health Care for the Homeless Council data portal to help understand the impact of COVID-19 on the staff and clients of homeless sheltersexternal icon and encampments.

Table 2. Community Indicators at the County Level@
Indicator Low Moderate Substantial High
Cumulative number of new cases per 100,000 persons within the last 7 days* >10 10–49 50–99 >100
Percentage of NAATs that are positive during the last 7 days >5% 5%–7.9% 8%–9.9% >10%

Indicators should be calculated for counties or core based statistical areas, although in rural areas with low population density, multiple jurisdictions might need to be combined to make the indicators more useful for decision-making. The indicators listed can be found by county on CDC’s COVID Data Tracker Website under “county view.”

@ If the two indicators suggest different transmission levels, the higher level should be selected.

* Number of new cases in the county (or other administrative level) in the last 7 days divided by the population in the county (or other administrative level) and multiplying by 100,000.

† Number of positive tests in the county (or other administrative level) during the last 7 days divided by the total number of tests resulted in the county (or other administrative level) during the last 7 days. Calculating Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Laboratory Test Percent Positivity: CDC Methods and Considerations for Comparisons and Interpretation.

Table 3. Potential Actions based on Community Indicator Level
Prevention Strategy Low Transmission
(Blue)
Moderate Transmission (Yellow) Substantial Transmission (Orange) High Transmission (Red)
Conduct standard case identification and investigation**
Implement screening testing: Test subsets of individuals according to designated criteria***

Implement screening testing: Increase frequency of testing subsets of individuals according to designated criteria***
Screening testing: Continue testing subsets on regular basis; consider facility-wide testing at least weekly
Implement facility-wide testing if:
  • A positive test result is identified at the site,
  • A positive test result is identified in a sentinel site,****
  • A cluster of probable cases at the site exceeds a pre-determined threshold, or
  • A site is identified in location-based contact tracing.
Implement facility-wide testing at least weekly with follow-up testing if cases are identified

*Levels of community transmission defined as total new cases per 100,000 persons in the past 7 days (low, 0-9; moderate, 10-49; substantial, 50-99; high, ≥100) and percentage of positive tests in the past 7 days (low, <5%; moderate, 5-7.9%; substantial, 8-9.9%; high, ≥10%).

**Passive surveillance using laboratory-based surveillance and case investigation.

***Active surveillance; see below for example criteria.

****Sentinel site=a site that provides a signal for whether outbreaks might be occurring at adjacent sites.

Community transmission phase: Low

Health departments use standard surveillancepdf iconexternal icon (passive) and case investigation processes.

  • Investigate whether SARS-CoV-2-infected individuals have been affiliated with any homeless service site or encampment from 48 hours before they had symptoms until they were isolated.
  • Offer SARS-CoV-2 viral testing to all clients and staff affiliated with the site or encampment any time from 48 hours before the individual began experiencing symptoms (or 2 days before a positive test in an asymptomatic individual), until that person was isolated.
  • Review CDC guidance for responding to cases at homeless service sites for further information about case investigation and outbreak response.

Screening testing may be considered by state or local health authorities.

Community transmission phase: Moderate

Health departments can consider offering systematic testing to individuals affiliated with the site according to designated criteria to increase the likelihood of early identification of cases (active surveillance).

  • Enhanced symptom-based testing access: Station medical providers at homeless service sites to offer testing to anyone with symptoms of COVID-19. If this yields a positive test, conduct facility-wide testing.
  • Random-selection screening testing: Offer screening testing to randomly selected (e.g., every third person) clients, staff, or volunteers at the site on a regular basis such as weekly. Testing should occur at least weekly. If this yields a positive test, conduct facility-wide testing.
  • Setting positive symptom screening thresholds: Track COVID-19-like illness (probable casespdf iconexternal icon) at the site if testing is pending or not available.
  • Sentinel sites: Choose a single site to conduct facility-wide screening testing on a regular basis such as weekly. Consider connected sites to be sentinel sites for each other such as correctional facilities or nearby homeless service provider sites. If one or more cases is identified in the sentinel site, conduct facility-wide screening testing at each site.

Community transmission phase: Substantial

Health departments and healthcare providers can consider screening testing at higher frequency. If any cases are detected, facility-wide testing and other mitigation measures should then be conducted to interrupt transmission.

  • Combine screening strategies such as offering both enhanced symptom-based screening and random-selection screening.
  • Increase the frequency of random screening testing and the number of people tested at each site. In screening settings where antigen tests are used, confirmatory NAAT testing is recommended for individuals who test positive. For interpretation of screening test results, please see the Antigen Test Algorithm pdf icon[457 KB, 1 page]. Persons with a positive test (NAAT or antigen) should be isolated either on site or at an isolation facility. They should remain in isolation until they have met the criteria for discontinuation.

Community transmission phase: High

Health departments continue regular screening and may consider coordinating with partners to offer facility-wide screening testing for all clients, volunteers, and staff in all sites weekly, regardless of whether an initial case of COVID-19 has been identified. Repeat testing of all previously negative or untested clients, staff, and volunteers weekly until the testing identifies no new cases of COVID-19 for at least 14 days since the most recent positive result. If resources for testing are limited, sites can be prioritized according to one or more of these factors: larger size, higher turnover, higher connectedness (staff or client overlap) with other facilities, more crowding (less space), more congregate rooms (fewer individual rooms), vulnerability of population (disproportionate risk or relatively higher risk for severe illness).