This Is How Long You Stay Contagious With COVID, Data Shows
Research shows how likely you are to spread the virus to others over time.
For nearly two years, people were told to isolate for 10 days after testing positive for COVID or developing symptoms. But on Dec. 27, the Centers for Disease Control and Prevention (CDC) made a controversial change to its guidelines, shortening the recommended time for isolation to just five days instead of more than a week. This decision was motivated by science that suggests COVID transmission mostly occurs earlier in the course of the illness, per the CDC. The agency has been criticized for the change, in part because experts worry it adds to the confusion of how long people can spread the virus to others. With that in mind, read on to learn what data shows about how long you stay contagious with COVID.
You can be contagious with COVID for more than 10 days.
There is no one standard for how long you could be spreading the virus, but some people can remain contagious for more than a week. COVID patients are "potentially infectious" two days before their symptoms arise and up to ten days after, Gary McLean, PhD, a professor of molecular immunology at London Metropolitan University, told Insider.
The U.K. Health Health and Security Agency (UKSHA), which helps inform COVID policies in the country, released data from its modeling study at the end of December, which gives insight into the potential periods of infectiousness for most patients. According to their data, about 5 percent of people who tested positive for COVID are still infectious after 10 days of self-isolation. And at least 1 percent might still be contagious 14 days after testing positive or developing symptoms.
But most people have a shorter period of contagiousness.
More people are infectious for a shorter period of time than this, however. According to the UKSHA data, around 16 percent of people are still contagious seven days after developing symptoms or testing positive for COVID. But at day five, which has become the new isolation benchmark in the U.S., 31 percent of people are estimated to remain infectious after symptom onset or a positive test.
"During the course of a SARS-CoV-2 infection, viral load increases from 1 to 2 days before symptom onset, then peaks at symptom onset and in the first 5 days, indicating that this period has highest infectiousness potential," the agency's report states.
According to the CDC, the risk of being contagious for longer than a week is only higher for certain people. "The likelihood of recovering replication-competent (infectious) virus is very low after 10 days from onset of symptoms, except in people who have severe COVID-19 or who are moderately or severely immunocompromised," the agency says.
People with Omicron might stay infectious longer.
On the other hand, past data might be somewhat inconsistent for the latest variant. A Japanese report released on Jan. 5 suggests that patients with the Omicron variant of COVID may shed the virus for longer after symptoms emerge than with prior versions of the virus. According to this report, preliminary data from the National Institute of Infectious Diseases, which conducts disease surveillance in Japan, shows that a patient's viral load is highest three to six days after testing positive or developing symptoms.
Paul Hunter, a professor in medicine at the University of East Anglia, said that the latest Japanese data "muddy the waters," according to an article on the report published in the BMJ on Jan. 13. While peak transmission with previous variants was between two days before symptoms and three days after, the new data indicates that the peak of virus shedding may be two or three days later with Omicron, Hunter said.
If you still have certain symptoms, you should stay home.
The CDC's guidelines have been updated to say that symptomatic people can leave isolation five days after onset only if their symptoms are improving and they have been fever-free for at lest 24 hours, without the use of fever-reducing medication. "Loss of taste and smell may persist for weeks or months after recovery and need not delay the end of isolation," the agency notes.
Julie Parsonnet, MD, an infectious diseases epidemiologist with Stanford Medicine, told Healthline that in general, people who have tested positive for COVID and are symptomatic are more at risk of spreading the virus to others. So if you still have certain symptoms, you shouldn't go out, especially if you have symptoms that can release respiratory droplets easily. "People whose symptoms are not improving—particularly if they have coughing and sneezing—should continue to stay home until they're feeling better," Parsonnet said.
And while this isn't an exact science, experts say it's likely the best course of action people can take to make sure they're not sending the virus off to other people. "We don't exactly how symptom duration relates to how long someone is contagious, but we do typically associate symptoms like fever as indication that someone is still infectious," John Carlo, MD, the CEO of Prism Health North Texas and member of the Texas Medical Association COVID-19 Task Force, explained to Healthline.