More people are receiving multiple negative COVID tests before finally testing positive following exposure or symptoms with newer subvariants circulating, Chicago's top doctor said Thursday.
The reason behind the shift could be due to vaccinations.
"We think some of that is because, especially if people are fully vaccinated and or if they've had COVID before, they're not always...they're not getting as sick," Chicago Department of Public Health Commissioner Dr. Allison Arwady said. "They're like not learning as much of an immune response and it can take a little bit longer sometimes for that test to turn positive. The good news is, generally... if the home test is negative, you're not very likely to have enough virus to be spreading, to be contagious."
Arwady noted that PCR tests are more sensitive than at-home tests, but said anyone experiencing symptoms or who may have been exposed should mask for the full 10 days, regardless of their test results.
According to the Centers for Disease Control and Prevention, "positive results from self-tests are highly reliable."
Negative results, however, may not rule out infection, particularly in those with COVID-19 symptoms, the CDC states.
The CDC recommends those who test negative, test again 24-48 hours after their first test.
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"Consider repeating the test 24 to 48 hours later," the guidance states. "Multiple negative tests increases the confidence that you are not infected with the virus that causes COVID-19."
While PCR tests can be more effective at detecting the virus, some people who contract COVID-19 can have detectable virus for up to three months, though that doesn't mean they are contagious.
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When it comes to testing, the PCR tests are more likely to continue picking up the virus following infection.
"PCR test can stay positive for a long time," Arwady said in March.
"Those PCR tests are very sensitive," she added. "They keep picking up dead virus in your nose for sometimes for weeks, but you can't grow that virus in the lab. You can't spread it, but it can be positive."
The CDC notes that tests "are best used early in the course of illness to diagnose COVID-19 and are not authorized by the U.S. Food and Drug Administration to evaluate duration of infectiousness."
For those isolating due to a COVID infection, there is no testing requirement to end isolation, however, the CDC recommends using a rapid antigen test for those who choose to take one.
The CDC says those with symptoms should test immediately. Those who were exposed but don't have symptoms should test five days after exposure.
According to earlier CDC guidance, COVID symptoms can appear anywhere from two to 14 days after someone is exposed to the virus.
Anyone exhibiting symptoms should get tested for COVID-19.
Some people may never experience symptoms, though they can still spread the virus.
A person is also considered contagious before symptoms appear.
Arwady noted that milder cases of the virus can make determining symptoms more challenging.
"We're seeing a lot of COVID that is often quite mild," she said, though she added that some early studies may show more intense illness specifically with newer BA.4 and BA.5 subvariants.
"With BA4 and BA.5 in particular, there were some animal studies that showed, for example, a little more what we call pathogenic, a little more problematic like in some of the animal lungs and stuff where tests were done- mice, etc.," Arwady said. "And potentially BA.4, BA.5 could be could be a little more intense, but overall, I think, you know, if you're vaxxed and boosted, I just say thank goodness you're vaxxed and boosted if you are having, you know, significant symptoms, because that's a sign that you could have gotten even sicker."
According to the CDC, the following are symptoms of a COVID infection:
- Fever or chills
- Cough
- Shortness of breath or difficulty breathing
- Fatigue
- Muscle or body aches
- Headache
- New loss of taste or smell
- Sore throat
- Congestion or runny nose
- Nausea or vomiting
- Diarrhea
Arwady said that while symptoms don't appear to be changing, there's one misconception she wanted to clear up.
"We do continue... for some reason people have been telling me they don't think you lose taste and smell with omicron. You can lose taste as well with omicron. We've seen plenty of people have this temporary loss of taste and smell, that continues to be the most specific like if somebody has lost taste or smell I'm like, 'That's COVID.'"
