Covid symptoms may change, but the appearance of a pink line on a rapid test means one thing for sure: five days of isolation.

The guidance, from the Centers for Disease Control and Prevention, has been in place since late 2021. At the moment, the agency doesn’t appear to be making any changes to the policy.

But in some cases, telling people to isolate after a positive test may have an unintended effect. 

Dr. Victoria Valencia, interim director for the Health Center for Student Care at Tulane University in New Orleans, said that she and her staff saw an uptick in Covid when students returned to campus in August. But that is no longer the case, as students now tend to decline Covid testing. 

“Students are afraid of being diagnosed with Covid” because they don’t want to isolate, Valencia said.

So is five days of isolation really best? Here’s what experts say.

Where did the five-day isolation come from?

The current recommendation to isolate for five days is a “hangover” from when the CDC moved from a 10-day isolation recommendation to five days in late 2021, just as the first wave of omicron was taking hold in the U.S., said Harvard University epidemiologist Bill Hanage.

“It was not a reflection of evidence-based” science, he said. “It was there to stop everything from falling apart.”

At that time, a large chunk of the population was testing positive all at once because of the highly contagious variant. Recommending that everyone stay home — and out of work — for 10 days would have brought the country to a halt once again, so the five-day plan was put in place.

“If you look at the safety of the public, and the need to have society not disrupted, this was a good choice,” Dr. Anthony Fauci, former scientific adviser to the Biden administration, said at the time about the isolation recommendation.

There was also evidence that people are most contagious during those first five days of infection. That remains the most reliable scientific data, experts say.

“We know that most people with Covid-19 shed enough virus that they are likely still contagious for at least five days,” Jennifer Nuzzo, director of the Pandemic Center at Brown University School of Public Health, wrote in an email.

When the Covid public health emergency expired in May 2023, health officials in Oregon decided it was also time to pull back on the five-day isolation recommendation. Instead, the Oregon Health Authority suggested that people with Covid stay home only until they’ve gone without spiking a fever for 24 hours and are generally feeling better.

In January of this year, California health officials issued the same guidance.

“The ending of the public health emergency declaration doesn’t change biology,” Nuzzo said when Oregon changed its isolation recommendations. “I don’t see a biological reason to end the five-day isolation period.”

What we know about being contagious

People with the flu are most contagious the first three or four days after the illness begins, according to the CDC. People who test positive for influenza are advised to stay home “until at least 24 hours after their fever is gone” without the use of fever-reducing drugs, such as Tylenol.

A positive Covid-19 test on May 2, 2022 in San Anselmo, Calif.
A positive Covid-19 test. Rapid tests do work with the omicron virus.Justin Sullivan / Getty Images

A common cold virus is most contagious within the first few days but can continue to spread for up to two weeks, according to Johns Hopkins All Children’s Hospital research.

Like other viruses, people with Covid have varying degrees of sickness.

A set number of days to isolate is “dumb if you think about it from a medical perspective,” said Dr. Peter Chin-Hong, an infectious diseases specialist at the University of California, San Francisco.

More on Covid and contagiousness

“If you’re feeling fine the entire five days and have absolutely no symptoms, staying at home by yourself is not the same as somebody who’s had symptoms and then after five days, they’re going out and coughing on everyone,” Chin-Hong said. “The symptoms approach makes more sense, not just for Covid, but for lots of other infectious diseases that people don’t normally isolate for.”

Saskia Popescu, an assistant professor of epidemiology and public health at the University of Maryland School of Medicine, said that while a person’s risk of spreading Covid is in the first five days of infection, “we know increasingly, that even without symptoms, or upon their resolution, people can still shed infectious virus.”

Popescu said that means that while the risk is lower after Day 5, it doesn’t mean there’s zero risk. “You should still try and stay home,” she said. “And if you absolutely need to, you can wear a mask.”

“Covid is a very unique infectious disease,” Popescu added. “Forty to 50% of cases are asymptomatic, or have such mild symptoms that people don’t even realize they have symptoms.”

Are there differences between children and adults?

In a study published in JAMA Pediatrics in October, researchers found that children ages 7 to 18 were infectious for a median of three days after a positive Covid test. By Day 5, the majority of the kids were no longer infectious. 

“My personal view is that five days is more than sufficient” for isolation, said senior study author Neeraj Sood, a professor of health policy, medicine and business at University of Southern California. Based on the findings, “maybe you could go with something a little shorter for kids.”

An earlier study, published in the New England Journal of Medicine in July 2022, found that adults were infectious for a median of five or six days.

Popescu, who wasn’t involved with either study, said the findings on children will probably be used moving forward for a lot of school-based decisions. 

“It’s helpful to see the three days,” Popescu said.

‘If you’re sick, stay away from people’

On an individual level, common sense should rule, Hanage said. If you’re sick, stay away from people most at risk for severe complications, such as older relatives.

“You wouldn’t want to give them something that would make them badly ill — whether it’s Covid, flu or even food poisoning,” he said.

Popescu agreed. 

“From an infectious disease perspective, we want people to stay home if they have symptoms,” she said. “And just because you don’t have Covid doesn’t mean that you don’t have another infectious disease that could pose a risk to those around you.”

Dr. Michael Mina, an immunologist and former assistant professor of epidemiology at the Harvard T.H. Chan School of Public Health, urged people to do the best they can and take precautions where possible.

“Nobody’s perfect,” Mina said. “If you can decrease your chances of spreading to others, that’s really good. That alone is very, very good. So if you can’t isolate for five days, or it’s been five days, but you recognize that you might still be infectious, wear a mask as much as you can, don’t attend really densely packed events, and stay away from vulnerable people.”

CORRECTION (June 12, 2023, 11:15 a.m. ET): A previous version of this article misstated Jennifer Nuzzo’s title and employer. She is director of the Pandemic Center at Brown University School of Public Health; she is not senior scholar at the Johns Hopkins Center for Health Security.

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