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.
- Jump straight to: My first COVID-19 test was negative. What do I do now?
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 you’re caught in a “Wait, so do I have COVID or not?” testing limbo.
It could take more time to test positive for COVID-19 than in years past
Some medical experts say they’ve noticed that at this stage of the pandemic, it’s often taking much longer for people to get a positive test result on an at-home COVID-19 antigen test. In other words, they’re 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 don’t 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 she’s 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 there’s 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-Hong’s advice in the last year has been that if you’re 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?
Your COVID-19 symptoms might be starting earlier
Right now, experts aren’t 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 body’s 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 person’s 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 don’t 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 body’s 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 you’ve 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 people’s accumulated immunity from COVID-19 over the years — either from getting infected or getting vaccinated.
“It’s actually pushing back the time that people’s COVID tests are coming up positive,” Hudson said.
The bottom line is: If you’re testing because you’ve started feeling unwell, it’s unwise to assume in 2024 that a negative result automatically means you don’t have COVID-19, because you might just be testing too early.
