Video Q&A: Dr. James Lewis on COVID testing

Videos produced by Leslie Daniels.

We all have questions about COVID-19, and there is a lot to learn when it comes to testing. You might know someone who felt sick after being exposed to COVID, but never tested positive. Or maybe you’re wondering if you should get tested sooner if you haven’t been vaccinated.

We sat down with medical epidemiologist Dr. James Lewis to answer three questions about testing we’ve heard a lot in our community:

  1. Can I have COVID and still test negative?
  2. If I have symptoms after being exposed to COVID, should I get tested?
  3. How soon should I get tested if I haven’t been vaccinated or already had COVID?

See James’ video and written answers to these questions below.

Note: Dr. James Lewis served as a medical epidemiologist supporting King County’s COVID-19 response for more than two years, before recently accepting a position as Health Officer for Snohomish Health District. Thank you to James for taking the time to answer these questions, and wishing you the best in your new role!

Can I have COVID and still test negative?

Dr. James Lewis: It is certainly possible to test negative and be infectious with COVID.

The most important thing is to test multiple times, and with Omicron, it seems that more and more people are testing positive after days of symptoms. So it’s really important to do multiple tests, especially at least 4 to 5 days after your symptoms start.

There is research that shows people who have a positive antigen test are much more likely to be infectious than people who have a negative antigen test.

One of the theories about why you can test negative and still have symptoms is that in people who have had a previous infection or in people who are immunized, your immune system is really primed to fight the infection.

So your immune system revs up really quick as soon as the virus gets into your body, preventing the virus from getting to a high enough level in your body to actually be able to be found by the tests.

Another potential issue would be just getting a good enough sample. So you really need to follow carefully the instructions for use that come with the test, and really try to get a good sample on that on that swab.

If I have symptoms after being exposed to COVID, should I get tested?

Dr. James Lewis: Yes. Any time you have been exposed to COVID and you develop symptoms, you should get tested right away.

It is really important if you test negative to do at least one more repeat test 4 to 5 after symptoms start.

But I would encourage further testing as well, especially if you continue to test negative and continue to have symptoms. So testing every 24 to 48 hours is very appropriate, especially while you’re symptomatic.

Even if you don’t develop symptoms and you’ve had a close exposure to someone diagnosed with COVID 19, it’s not wrong to go ahead and continue to test yourself as well after that exposure. So you can test yourself 3 to 5 days after that exposure, and consider again testing subsequently to that, even if you continue not to have symptoms.

How soon should I get tested if I haven’t been vaccinated or already had COVID?

Dr. James Lewis: If you haven’t been vaccinated and you’ve never had COVID, it may take your immune system a little bit longer to fight off the virus.

And so you may be more likely to test positive earlier, perhaps even before you start developing symptoms.

If you’ve not been previously infected that you know of and you’re not immunized, and you know you’ve been exposed, it would be good to go ahead and still test 3 to 5 days after that exposure.

And that’s especially important for those folks with no previous infection or who haven’t been immunized, to test 3 to 5 days after that exposure, because they’re much more likely to get infected. And they’re more likely to not necessarily have symptoms by the time they start actually being infectious to other people.

For more frequently asked questions about COVID testing and guidance, visit:

Originally posted on July 8, 2022.