Why Your Negative COVID Test Might Be Less Reliable in 2024 – KQED

Jan 11

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A whole host of winter respiratory viruses is circulating in the first weeks of 2024 which means you probably know several people who are sick right now. And for a fourth January running, we still have to worry about COVID-19.

At this stage in the pandemic, worrying that your sore throat, cough or congestion might, in fact, be COVID-19 is a natural thought, especially as the Bay Area is experiencing another wave of infections fueled by the new JN.1 strain.

But while testing negative on an at-home antigen test can bring some relief, unfortunately, you may no longer be able to trust that initial result in the way you could earlier in the pandemic.

Keep reading for what you need to know about COVID-19 incubation periods in 2024, why an early negative test could be a false result, and what to do if youre caught in a Wait, so do I have COVID or not? testing limbo.

Some medical experts say theyve noticed that at this stage of the pandemic, its often taking much longer for people to get a positive test result on an at-home COVID-19 antigen test. In other words, theyre observing that people with COVID-19 symptoms are taking an antigen test and getting a negative result only to get a positive result on a different test several days later.

This means that many people could wrongly assume they dont have COVID-19 after that first negative test and then inadvertently spread the virus to friends and family.

Dr. Peter Chin-Hong, an infectious disease expert at UCSF, said he and his colleagues are now seeing people take longer to get a positive test even though they have COVID-19 symptoms. Dr. Elizabeth Hudson, regional chief of infectious diseases at Kaiser Permanente Southern California, told the Los Angeles Times that shes also noticed this delay and that a patient might not get a positive test result up until the fourth day after the start of their symptoms.

But theres a confusing additional aspect to this too: Paradoxically, said Chin-Hong, incubation times for the virus have gotten shorter throughout the pandemic. This means people have tested positive for COVID-19 more quickly than in 2020, when the average incubation period was five days because the incubation period has changed with each new variant. Chin-Hongs advice in the last year has been that if youre having COVID-19 symptoms, it now makes sense to take a test as early as two days after exposure.

So how do shorter incubation times square with this newly observed delay on positive COVID-19 tests?

Right now, experts arent 100% sure why antigen tests are taking longer to return a positive COVID-19 result. But Chin-Hong said that the hypothesis that makes sense to him is less about the efficacy of the antigen tests themselves and way more about how much quicker someone with COVID-19 might develop symptoms in 2024 than they would have done in 2020.

As a reminder, those symptoms are the sign that your bodys immune system is mounting a response to an invading virus and back at the start of the pandemic, by the time you developed COVID-19 symptoms and took a test it would probably already be positive, Chin-Hong said.

But at this stage of the pandemic, most of us now have a lot of immune experience with COVID-19, Chin-Hong said and the average persons immune system is increasingly on guard and activated more than in 2020, he said. So when your body detects a burgeoning coronavirus infection now, your whole immune system just gets agitated and active, and you begin to get sick sooner, but you actually dont have as much virus in your blood yet, Chin-Hong said.

Dr. Abraar Karan, an infectious disease physician and researcher at Stanford University, also put it this way for NPR: With our immune systems primed, the bodys response [now] comes much more quickly than it would have back in 2020 when SARS-CoV-2 was a novel pathogen.

And because many of us take a COVID-19 test when we start to feel sick, we might be testing way too early at that time for an at-home antigen kit to successfully detect enough virus inside us. This mismatch between when your symptoms start and when youve enough virus present in your body to result in a positive COVID-19 test was started to be observed in early omicron, but I think it just seems more accentuated now, Chin-Hong said.

However, Hudson of Kaiser Permanente Southern California told the L.A. Times that for her, this delay in positive tests might be attributable to peoples accumulated immunity from COVID-19over the years either from getting infected or getting vaccinated.

Its actually pushing back the time that peoples COVID tests are coming up positive, Hudson said.

The bottom line is: If youre testing because youve started feeling unwell, its unwise to assume in 2024 that a negative result automatically means you dont have COVID-19, because you might just be testing too early.

Experiencing the onset of symptoms that feel like COVID-19 is unpleasant and worrying enough. And now, this new possible delay around even knowing if you have COVID-19 adds another element of frustration and uncertainty to whats already a stressful situation. Even if youve been able to find free COVID-19 tests being given away or by order from the U.S. government via USPS, one COVID-19 scare in a family can run through that stockpile pretty fast and the cost of purchasing new COVID-19 antigen kits can really add up.

If youre in the limbo of not knowing whether you actually have COVID-19 yet, heres what to do:

If your first test is negative for COVID-19, test again later

If you have symptoms but have tested negative, dont assume it means youre COVID-free. The CDC recommends that you take another antigen test 48 hours laterand then test again after another 48 hours.

Chin-Hong advises that you can also seek out a PCR test, which is more sensitive.

While youre unsure, play it safe

If you have symptoms and dont know why yet for sure, stay home as much as you can. If you truly cant stay indoors and away from others, wear a well-fitted mask to protect your community and try to ensure youre in well-ventilated spaces.

Be especially careful not to spread any virus around folks who are at higher risk for serious illness or hospitalization from COVID-19, which includes older people, immunocompromised and disabled people.

Remember: Just because its not COVID-19 doesnt mean youre not still sick

Even if you turn out not to have COVID-19 after several days of testing but youre still experiencing symptoms, you might still be infected with one of the other highly infectious winter respiratory viruses out there like flu, RSV or a bad cold. And if youre sick, you could easily infect your friends, family or colleagues with whatever youre suffering from.

Give yourself permission not to trust a friends negative test, too

What if its a friend whos experiencing COVID-19 symptoms, and theyre insisting that theyre safe to meet with you because they took a test and its negative?

Knowing what you know that it can sometimes take folks longer to get a positive COVID-19 test in 2024 you should feel free to compassionately tell your friend that while you trust them, you cant trust an early negative test right now. Theres a good chance that they have no idea that positive tests can be increasingly delayed and will be relieved to know that by staying home, they havent accidentally spread an infectious disease to you or other loved ones.

And if they disagree and insist theyre still safe to meet up? You should feel free to decline, even if it feels awkward. Remember, its not weird to not want to get COVID-19.

Stock up on free COVID-19 tests

Finding a quick, free COVID-19 test whether an at-home antigen test or a PCR test has gotten progressively harder at this stage of the pandemic as more sites and services have shuttered. The federal government has, at least, restarted its free at-home COVID-test-ordering service through USPS, meaning you can once again order another four free antigen tests to be delivered to your door for a future time.

Read more about where to find free or low-cost COVID-19 tests this winter.

but make sure your COVID-19 tests havent expired

Many of the COVID-19 tests being made available right now (for example, at your local public library) may be approaching their expiration date if they havent already passed it. And an expired test could give you an unreliable result.

You can check the FDAs list of antigen test types to see whether the box youre holding has had its shelf life extended by the manufacturer. The FDA said that if a tests shelf life has been extended, its because the manufacturer has given the agency enough data showing that the shelf-life is longer than was known when the test was first authorized. (In other words, its still OK to use that test.)

At KQED News, we know that it can sometimes be hard to track down the answers to navigate life in the Bay Area. Weve published clear, practical explainers and guides about COVID-19, how to cope with intense winter weather, and how to exercise your right to protest safely.

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Why Your Negative COVID Test Might Be Less Reliable in 2024 - KQED