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Why it's taking people with COVID-19 so long to finally get a negative test

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As many hope to put the pandemic behind us, some are still suffering from one particular symptom. Veuer’s Tony Spitz has the details.

LOS ANGELES — Health officials recommend that anyone infected with the coronavirus isolate for at least five days. But for many, that timeline is becoming overly optimistic.

The isolation period, which the U.S. Centers for Disease Control and Prevention shortened in December from 10 days to five, is more a starting point than a hard-and-fast rule. According to the California Department of Public Health, exiting isolation after five days requires a negative result from a rapid test on or after the fifth day following the onset of symptoms or first positive test — a step not included in federal guidelines.

But many people don't start testing negative that early.

"If your test turns out to be positive after five days, don't be upset because the majority of people still test positive until at least Day 7, to Day 10 even," Dr. Clayton Chau, director of the Orange County Health Care Agency, said during a briefing Thursday. "So that's the majority. That's the norm."

But even typical, longer isolation periods carry very real effects, such as keeping people away from family and friends and out of work. While it may be disruptive, isolating is intended to stymie the spread of the coronavirus.

Dr. Robert Kosnik, director of UC San Francisco's occupational health program, said at a campus town hall in July that there's an expectation people will test negative on Day 5 and can return to work the next day.

"Don't get your hopes up," Kosnik told his colleagues. "Don't be disappointed if you're one of the group that continues to test positive."

In fact, some 60% to 70% of infected people still test positive on a rapid test five days after the onset of symptoms or their first positive test, meaning they should still stay in isolation, Kosnik said.

"It doesn't significantly fall off until Day 8," he said.


Shoppers, some wearing masks, are seen in Los Angeles on July 14, 2022.

A study published by the CDC in February found that 54% of patients had positive antigen tests between five and nine days after an initial diagnosis or the onset of symptoms, though "the proportion of positive results declined over time."

People with symptomatic COVID-19 were more likely to continue testing positive five to nine days after symptoms first appeared. In the study, 64% of symptomatic patients still tested positive in this time frame.

"However," the study noted, "a positive antigen test result does not necessarily mean that a person is infectious. Similarly, a negative test result does not necessarily mean that a person is not infectious. Nonetheless, a positive or negative antigen test might be a useful proxy for the risk for being infectious."

The proportion of positive test results "was lower after asymptomatic than symptomatic infection," researchers found.

In general, the study said, "lower prevalence of positive test results over time and after asymptomatic infections might reflect lower infectiousness."

Here's a summary on guidance for isolation from the California Department of Public Health:

Day 0: Start of COVID-19 symptoms or the day of your first positive coronavirus test, if you're asymptomatic. Wear a highly protective mask around others if in the same room as others in your home.

Days 1-5: Remain in isolation.

Day 5: You can take a rapid test. If you test negative, don't have a fever and your symptoms are improving, you can exit isolation on Day 6.

Days 6-10: You can end isolation if your rapid test result — taken on Day 5 or later — is negative, you've been fever-free for 24 hours without taking fever-reducing medicines and your symptoms are improving or you don't have symptoms.

Day 11: You can generally end isolation without needing a negative rapid test result. But if you still have a fever, stay isolated until 24 hours after the fever ends. And if you are immunocompromised or have had severe COVID-19, you might need to isolate longer.

"If you do not have access to an antigen test, then we feel pretty comfortable that 10 days after your symptoms start, you are no longer infectious," Orange County Deputy Health Officer Dr. Matthew Zahn said.

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