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Coronavirus and COVID-19 Information: Santa Clara County and Bay Area, California

Trustworthy information about COVID-19

Screening & Testing for COVID-19 Infection

The first publicly available tests (in the U.S.) for this disease use a swab in nose and throat passages, That sample is then examined for coronavirus RNA fragments, and a positive test result means that there is an active COVID-19 infection.

Processing these tests can take a few days to get results. Those few days can make a big difference in how seriously ill someone can become, or in how many people can be infected through contact - so don't wait for test results before taking precautions!

Here are links to testing locations in the Bay Area. Please note: some are only available to patients enrolled in that system, others accept patients with any or no health insurance.

Both the state of California and the US government have declared that testing should be free of charge, regardless of whether you have health insurance or are not insured. If you do get a bill for a COVID-19 test, this link has details on what to do to contest that:

(However, being treated for COVID-19 is another matter. For more information on help with medical costs of treating COVID-19, use the page in this guide In for the Long Haul.)

Who Should Get Tested?

Should you get tested if you think you've come into contact with someone who has COVID-19, or who you suspect has it? 

People whop have been fully vaccinated (at least 14 days after their last vaccine dose) do not need to get tested unless they have symptoms of COVID-19 or unless their work requires a test.

Unvaccinated people should absolutely get tested!

When to get tested can be a tricky question. Testing too early, before an infection takes hold, can give a false negative test, and could end up spreading the novel coronavirus. Studies have found that swab tests are most accurate sometime between day day 4 and day 10 after exposure, usually 2 days before symptoms appear. If you think you may have been exposed at a specific event, follow this timeline from Santa Clara County Public Health:

Quarantine Timeline, Santa Clara County Dept. of Public Health as of Dec. 12, 2020

Contact Tracing

If a COVID test is positive, you are likely to hear from a contact tracer.


A contract tracer should only ask questions about your COVID-19 symptoms or status, and about the people you may have had contact in a specific period of time.

Legitimate contact tracers will never ask you for a Social Security number or about immigration status, for any health insurance or financial information. (If you are asked any of those questions, the call may be a scam. Please do not give out those details, and make a complaint to the CA State Attorney General.)

Contact tracing in-person is a labor-intensive process, and our memories can be fallible. To help automate that process while at the same time protecting our privacy, a new phone app is available in California. For more details, see:

Testing for COVID-19 antibodies

Because so many people have no symptoms with this disease, the only way to tell who has had it - and who might be immune to the current version of this virus - is to look for antibodies in their systems. Several different trial versions of antibody tests are being used and tested, but as of this writing, none of them have reliable accuracy. Since these all involve testing for various substances in the blood, these are referred to as serologic tests.

On May 23, 2020, The CDC released guidance on serologic [blood] tests which included these strong recommendations [emphasis added]:

  • Serologic testing should not be used to determine immune status in individuals until the presence, durability, and duration of immunity is established.
  • Serologic test results should not be used to make decisions about grouping persons residing in or being admitted to congregate settings, such as schools, dormitories, or correctional facilities.
  • Serologic test results should not be used to make decisions about returning persons to the workplace.

However, blood tests are useful in these ways:

  • Serologic testing can be offered as a method to support diagnosis of acute COVID-19 illness for persons who present late [i.e., after symptoms have passed, to determine if it really was COVID-19].
  • Serologic testing should be offered as a method to help establish a diagnosis when patients present with late complications of COVID-19 illness, such as multisystem inflammatory syndrome in children.

Ultimately, without reliable antibody testing, we cannot have good data on the spread of COVID-19 .

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