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See Isolation & Quarantine Guidance below.


Safe, easy, no-cost testing is widely available at County-sponsored locations, private testing companies, pharmacies, and through at-home test kits available for purchase at pharmacies and other retailers.

There are two types of COVID-19 test: Polymerase chain reaction (PCR) tests, which typically return results within 72 hours, although times vary depending upon demand and rapid antigen tests, often referred to as at-home test kits, which return results in a few minutes.

Results from PCR tests are reported by laboratories to San Mateo County Health, which provides the information to the California Department of Public Health. Results from rapid-antigen tests are not reported to public health officials, and San Mateo County Health is not collecting the results.

The County of San Mateo offers only PCR testing at 10 sites, which it operates through contracted providers Curative and LHI/OptumServe.


According to guidance from the California Department of Public Health:

  • You should get tested immediately for COVID-19 if you are feeling any symptoms – regardless of your vaccination status. COVID-19 symptoms can feel like a common cold (including just “the sniffles”), seasonal allergies, or flu. Symptoms include fever or chills, cough, shortness of breath, and difficulty breathing. If an antigen test is negative, take another in 24-48 hours, as early cases can be missed.
  • If you’ve been exposed to COVID-19 you should consider getting tested as soon as possible, even if you have no symptoms. Test again 5 days after exposure.
  • If you go to a high-risk event, you should test before and 3-5 days after.
  • If you travel domestically (within the U.S.), test as close to your time of departure as possible (no more than 3 days) before travel and test after travel.

The CDPH testing fact sheet is here, and CDPH guidance related to travel is here.


If you test positive on a PCR test, you may receive a text message from the number 23393. San Mateo County Health uses the state of California’s text-message-based virtual assistant to provide information, connect you to resources, and collect more information from you. It is safe to click on the link and start communicating with San Mateo County Health through the Virtual Assistant.

Learn more about the Virtual Assistant here.

Your responses, which are confidential, will help determine if anyone near you, including your family and friends, is at risk of exposure to COVID-19. We will not ask for your social security number, immigration status, or financial information. Depending on their vaccination, your close contacts may be offered testing and may be asked to quarantine themselves to help prevent the spread of the disease, even if they are not showing symptoms.


San Mateo County Health is following guidelines from the California Department of Public Health (CDPH) on Isolation and Quarantine of the General Public and Use of Masks. CDPH provides an additional factsheet on Isolation and Quarantine if you have tested positive for COVID-19.

CDPH offers additional guidance on work exclusion and quarantine for High Risk Exposures and Settings

Persons Who Test Positive for COVID-19 (Isolation) Recommended Action

Everyone, regardless of vaccination status, previous infection or lack of symptoms.

  • Stay home for at least 5 days after start of symptoms (or after date of first positive test if no symptoms). 
  • Isolation can end after day 5 if symptoms are not present or are resolving and a test performed on day 5 or later is negative.
  • If unable to test or choosing not to test, and symptoms are not present or are resolving, isolation can end after day 10.
  • If fever is present, isolation should be continued until 24 hours after fever resolves. 
  • If symptoms, other than fever, are not resolving continue to isolate until symptoms are resolving or until after day 10.
  • Per CDPH masking guidance, it is strongly recommended that persons wear a well-fitting mask around others for a total of 10 days, especially in indoor settings 
Asymptomatic Persons Who are Exposed to Someone with COVID-19 (No Quarantine)  Recommended Action
  • Everyone, regardless of vaccination status.
  • Persons infected within the prior 90 days do not need to be tested, quarantined, or excluded from work unless symptoms develop.
  • Test between 3-5 days after last exposure. 
  • Per CDPH masking guidance, close contacts should wear a well-fitting mask around others for a total of 10 days, especially in indoor settings and when near those at higher risk for severe COVID-19 disease 
  • Strongly encouraged to get vaccinated or boosted
  • If testing positive, follow isolation recommendations above.
  • If symptoms develop, test and stay home.