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Testing for COVID-19 results in the identification of individuals with COVID-19 infection, which helps individuals get appropriate treatment. In addition, viral testing for COVID-19 identifies individuals with COVID-19 infection who are infectious and should isolate. By isolating infectious individuals, we can stop the spread of COVID-19. Testing is one layer in a multi-layered approach to COVID-19 prevention, in addition to other key measures such as vaccination, mask wearing, improved ventilation, physical distancing, respiratory and hand hygiene, and cleaning and disinfection.
Due to the elevated risk of COVID-19 transmission in certain high-risk settings, people in California may be required to undergo diagnostic screening testing or pre-entry testing. See CDPH guidance and State Public Health Officer Orders for more specific testing requirements for workers or visitors in health care settings, schools, high-risk congregate settings, and more. See Diagnostic Screening Testing and Pre-Entry Testing sections below for more details and specific requirements.
Local health jurisdictions may modify these guidelines to account for local conditions or patterns of transmission and may impose stricter requirements than those applicable statewide. Additionally, the California Department of Public Health (CDPH) will continue to reassess this guidance and relevant health orders and adjust them accordingly based on emerging evidence and U.S. Centers for Disease Control and Prevention (CDC) updates.
Diagnostic testing for COVID-19 is used to diagnose an individual with SARS-CoV-2 infection. SARS-CoV-2 is the virus that causes COVID-19.
CDC's list of symptoms of COVID-19 includes fever or chills, cough, shortness of breath or difficulty breathing, fatigue, muscle or body aches, headache, new loss of taste or smell, sore throat, congestion or runny nose, nausea or vomiting, and diarrhea. Severe symptoms of COVID-19 include but are not limited to trouble breathing, persistent pain or pressure in the chest, new confusion, inability to wake or stay awake, pale, gray, or blue-colored skin, lips, or nail beds, depending on skin tone. Symptom lists are available at the CDC symptoms and testing page.
Diagnostic testing should be considered for all individuals with symptoms of or exposure to COVID-19.
Diagnostic testing may be performed using either molecular testing or antigen testing (see details on antigen and molecular testing below in the tests section). See CDPH Guidance for additional information on testing in different settings.
Diagnostic screening testing is recurrent testing of asymptomatic individuals to detect COVID-19 early, stop transmission, and prevent outbreaks.
Diagnostic screening testing can be used as a public health strategy to identify individuals who have COVID-19 and are infectious but have no or very mild symptoms and have them isolate so that they do not spread infection to others. The CDC estimates that up to 60% of COVID-19 infections are transmitted while infected individuals are asymptomatic (including people who are pre-symptomatic and those who never develop symptoms). Unvaccinated individuals have a higher likelihood of contracting and thus spreading illness. The goal of diagnostic screening testing is to detect cases early, isolate infected individuals and prevent the spread of COVID-19.
Fully vaccinated individuals  are not required to undergo routine diagnostic screening testing in non-healthcare settings including workplaces and schools. It is important to note that if an individual is symptomatic, even if fully vaccinated, diagnostic testing should be performed.
Many non-healthcare settings require diagnostic screening testing of individuals who are not fully vaccinated. See the State Public Health Officer Orders (SPHOs) for Health Care Worker Protections in High-Risk Settings and Vaccine Verification for Workers in Schools for more information on diagnostic screening testing requirements for unvaccinated individuals. For high-risk workplace settings where diagnostic screening testing is not required, it is still recommended for individuals who are not fully vaccinated.
Employees (Healthcare Personnel – HCP) in Acute Health Care and Long-Term Care Facilities are required to be fully vaccinated or to have received their first dose of a one-dose regimen or their second dose of a two-dose COVID-19 vaccine regimen by September 30, 2021. The only exemption to mandatory vaccination is a medical or religious exemption granted by the employer. See the SPHO for Health Care Worker Protections in High-Risk Settings, the SPHO for Health Care Worker Vaccine Requirement, and the SPHO for State and Local Correctional Facilities and Detention Centers for more details.
Diagnostic screening testing of asymptomatic unvaccinated or incompletely vaccinated HCP who have a COVID-19 vaccine exemption is required in hospitals (AFL 21-27) and SNF (AFL 21-28). Unvaccinated or incompletely vaccinated HCP shall be tested at the frequency specified for their work schedule in AFL 21-27 or AFL 21-28 with either antigen or molecular testing. Exempt unvaccinated or incompletely vaccinated HCP must observe all other infection control requirements, including masking, and are not exempted from the testing requirement even if they have a medical contraindication to vaccination, since they are still potentially able to spread the virus. Previous history of COVID-19 infection from which the individual recovered more than 90 days ago, or a previous positive antibody test for COVID-19, does not waive the requirement for testing.
Diagnostic screening testing of asymptomatic fully vaccinated HCP may be required in certain circumstances. Please refer to AFL 20-88.2 (hospitals) or AFL 20-53.5 (SNF) and the most recent SPHO to determine if testing is required for fully vaccinated HCP in your facility. If diagnostic screening testing of fully vaccinated HCP is not required, facilities may consider routine diagnostic screening testing for those with underlying immunocompromising conditions (e.g., organ transplantation, cancer treatment), which might impact the level of protection provided by COVID-19 vaccines. However, data on which immunocompromising conditions might affect response to COVID-19 vaccines and the magnitude of risk are not currently available.
Employers who conduct workplace diagnostic screening testing should have a plan in place for tracking test results, conducting workplace contact tracing, and reporting testing results to local public health departments. IT platforms are available that can facilitate this for employers. Employers should also consult CDPH/CDC guidance on workplace screening testing for additional information. Testing is an important complement to other COVID-19 prevention measures, such as vaccination, mask wearing, physical distancing, improved ventilation, respiratory and hand hygiene, and cleaning and disinfection.
Antigen or molecular tests used for diagnostic screening testing of individuals who are asymptomatic must either have Emergency Use Authorization by the U.S. Food and Drug Administration or be a test operating under the Laboratory Developed Test requirements of the U.S. Centers for Medicare and Medicaid Services. These tests need to be used at different minimum frequencies, please see below for details.
Refer to the SPHOs for Health Care Worker Protections in High-Risk Settings, State and Local Correctional Facilities and Detention Centers, Vaccine Verification for Workers in Schools, and Adult Care Facilities and Direct Care Worker Vaccine Requirement for additional information on minimum testing frequency required for healthcare settings, schools, and congregate settings. For more information on testing in schools, see CDPH 2021-2022 K-12 Schools Testing Framework (PDF) and 2021-2022 K-12 Schools Reopening Framework and Guidance.
Except where more frequent testing is required by a health order, the recommended minimum molecular test screening frequency is at least
once weekly. Molecular testing (PDF) is most effective when turnaround times are short (<2 days). If the turnaround time is longer than 2 days, screening testing with PCR or NAAT is a less effective screening method.
The current recommended minimum antigen test diagnostic screening test frequency is at least twice weekly.
More frequent testing improves outbreak prevention and control and is encouraged. Testing at a higher cadence can identify asymptomatic or pre-symptomatic cases early and permit them to be excluded from the setting to limit transmission.
Diagnostic screening testing is indicated for situations associated with higher risk, e.g., higher community transmission , individuals at higher risk of transmission, etc.
Post-exposure testing for COVID-19 means testing people who are asymptomatic but have been exposed to a confirmed or suspected case of COVID-19.
Individuals who are asymptomatic, and have not been fully vaccinated and have close contact  with someone who has tested positive for COVID-19 should be tested as soon as possible regardless of symptoms. If they test negative, they should retest 5-7 days after their exposure date even if they are asymptomatic. If they develop symptoms for COVID-19, they should be tested right away.
Consult Cal/OSHA COVID-19 Prevention Emergency Temporary Standard for current requirements for employers to offer testing of workplace close contacts after exposure.
Individuals who are asymptomatic, fully vaccinated, and have been in close contact with someone who tested positive for COVID-19 should be tested 5-7 days after the close contact occurred. If they develop symptoms for COVID-19, they should be tested right away.
Molecular or antigen tests can be used for post-exposure testing.
Response testing is repeat testing performed following an exposure that has occurred in high-risk residential congregate settings or high-risk/high-density workplaces. The goal of response testing is to identify asymptomatic infections in individuals in high-risk settings and/or outbreaks to prevent further spread of COVID-19. Response testing should be initiated as soon as possible after an individual in a high-risk setting has been identified as having COVID-19.
Response testing should occur for all individuals (residents and staff, regardless of vaccination status) in the facility as soon as possible after at least one individual (resident or staff) with COVID-19 is identified in a facility.
Either molecular or antigen testing can be used for response testing. It is recommended using the test with the fastest turn-around time that is available.
The recommended minimum response molecular test frequency is at least once weekly. Molecular testing (PDF) as a response testing tool is most effective when turnaround times are short (<2 days). If the turnaround time is longer than 2 days, response testing with molecular tests is not an effective screening method. Residents and staff should receive response testing regardless of their COVID-19 vaccination status.
The recommended minimum antigen response test frequency is at least every 3-7 days. Antigen tests conducted serially can be used for response testing in asymptomatic individuals if conducted at least twice weekly.
Response testing should be performed on all residents and staff initially, and then serial testing of those who tested negative on the prior round of testing should occur until no new cases are identified in sequential rounds of testing over a 14-day period. Facilities should work with their local health department to help with outbreak management.
Facilities must follow the CDPH and Local Health Jurisdiction recommendations where they exceed the Cal/OSHA standards.
Please note: unvaccinated exposed individual(s) should follow CDPH and CDC guidelines for quarantine after exposure, which can be found below in "Self-Quarantine (PDF)". Please refer to CDC guidelines for how to define an exposure to COVID-19.
Pre-entry testing is testing performed prior to someone entering an event, competition, congregate setting, or other venue or business and is intended to reduce the risk of COVID-19 transmission in these settings. Symptomatic individuals should not be allowed to enter.
Refer to CDPH Guidance for Mega Events for more information on pre-entry testing requirements for large indoor and recommendations for outdoor events, and to the State Public Health Officer Order for Visitors in Acute Health Care and Long-Term Care Settings for requirements for pre-entry testing for visitors in health care settings.
Individuals should have pre-entry testing performed if they have not been fully vaccinated and will be taking part in activities that put them or others at higher risk for COVID-19 exposure. In addition to settings where pre-entry testing is required, it should be considered for those attending large indoor social or mass gatherings (such as large private events, live performance events, sporting events, theme parks, etc.), high-risk sport competitions, or other events in crowded or poorly ventilated settings.
Fully vaccinated individuals do not need to undergo pre-entry testing.
Individuals who are not fully vaccinated and must travel should follow the pre-entry (pre–travel) testing recommendations in CDC travel guidance and CDPH guidance before and after travel.
CDPH recommends a point of care test (antigen or molecular) within 24 hours of entry for asymptomatic individuals. If point of care testing is not available, molecular testing of asymptomatic individuals within 72 hours of the event with results available before entry is recommended. In settings where testing is required by a State Public Health Order, either an antigen or molecular test is acceptable.
The following are acceptable as proof of a negative COVID-19 test result:
A printed document from the test provider or laboratory, OR
An electronic test result displayed on a phone or other device from the test provider or laboratory.
The information should include person's name, type of test performed, and negative test result.
Since there is a possibility of exposure to individuals infected with COVID-19 in gatherings and congregate situations, testing 3-5 days after the event and immediately if symptoms develop is recommended.
Individuals experiencing COVID-19-like symptoms (PDF) should obtain diagnostic testing and should not attend events or gatherings or visit congregate settings, irrespective of their test results.
There is no need to get tested after an initial positive confirmatory test to prove that an individual is no longer infectious and can end isolation. The end of isolation should be based on CDC and CDPH guidelines (PDF) (currently 10 days) and is based on the time from initial diagnosis or symptom onset. Individuals who had a positive viral diagnostic test in the past 90 days and are currently asymptomatic do not need to be retested as part of a diagnostic screening testing program; testing should be considered again if it is more than 90 days after the date of onset of the prior infection, or if new symptoms occur. Re-testing of Individuals who develop new symptoms consistent with COVID-19 during the three months after the date of initial symptom onset for which an alternative etiology cannot be identified, can be considered in consultation with infectious disease or infection control experts.
Molecular tests: Molecular tests amplify and then detect specific fragments of viral RNA. Depending on the test, different sequences of RNA may be targeted and amplified. Examples of this method include polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP), and Nucleic Acid Amplification Test (NAAT). The real-time reverse transcriptase polymerase chain reaction (PCR) is the most commonly used molecular test and the most sensitive test for COVID-19. PCR is typically performed in a laboratory and results typically take one to three days. Point-of-care (POC) molecular tests are also available and can produce results in 15 minutes but may have lower sensitivity (might not detect all active infections) compared with laboratory-based PCR tests.
Antigen tests: Antigen tests identify viral nucleocapsid protein fragments. They are typically performed at POC and produce results in approximately 10-30 minutes. POC antigen tests have a slightly lower sensitivity (may not detect all active infections), but similar specificity (likelihood of a negative test for those not infected with SARS CoV-2) for detecting SARS-CoV-2 compared to PCR tests.
In healthcare, long-term care and high-risk congregate settings:
In symptomatic individuals a negative antigen test requires molecular test (PCR, LAMP, NAAT) confirmation and individuals should isolate until test results are available. If an individual is asymptomatic and tests positive with an antigen-based test, individuals should isolate, and if confirmatory testing is desired to assess for false positive, repeat with a molecular test (PCR, LAMP, NAAT).
In all other settings:
Antigen tests are acceptable to determine both the presence or absence of active infection with SARS-CoV-2 in individuals with or without symptoms. Repeat antigen testing and/or confirmatory molecular testing should be considered in individuals who receive a negative result with an antigen test but have symptoms specific for COVID-19 (such as loss of taste and smell).
The FDA maintains a list of diagnostic tests for COVID-19 granted Emergency Use Authorization (EUA). No test is 100% accurate and test performance can vary depending on a number of test and patient factors as well as current community transmission rates and pre-test probability in the individual being tested. These recommendations for antigen testing and frequency are subject to change based on overall test positivity, local case rates and levels of transmission.
Viral Load: the amount of virus present in the testing site (e.g., nasal cavity) at a given time.
Sensitivity: ability of a test to turn positive when an individual is in fact infected with SARS CoV-2.
Specificity: ability of a test to be negative when an individual is not infected with SARS CoV-2.
Stage of Infection: Sensitivity is also highly dependent on the stage of the infection. In general, after exposure and infection the amount of detectable virus in the body remains low for the first few days of infection, then rises exponentially and then decreases gradually over a period of time.
Immune response of the infected individual: A person's individual immune response and their personal health characteristics can impact the time course of their infection, which will influence the level of viral load at any time point.
Different laboratories: Each lab's tests have their own sensitivity and specificity levels. Labs with a higher level of sensitivity can detect lower viral loads of COVID-19 that might not be detected by a test with a lower sensitivity level.
Different tests: Antigen tests and molecular tests have different limit of detection to detect virus thus impacting their sensitivities.
Sample collection and handling: Effective sample collection is dependent on different factors that can impact sample integrity including: collection technique and sealing of specimen, storage temperature, transportation, sample handling, and duration of time between sample collection and testing.
 Individuals are considered fully vaccinated for COVID-19 two weeks or more after they have received the second dose in a 2-dose series (Pfizer-BioNTech or Moderna), or two weeks or more after they have received a single-dose vaccine (Johnson and Johnson [J&J]/Janssen ), or other COVID-19 vaccines authorized for use by the US Food and Drug Administration or the World Health Organization. See CDPH Recommendations for Fully Vaccinated People for updates.
 Per CDC levels of community transmission definition: The indicators listed can be found by county on CDC's website with county view CDC COVID Data Tracker.
 Someone who was within six feet of an infected person for a cumulative total of 15 minutes or more over a 24-hour period.
Originally Published on June 7, 2021