Experts say the window of highest infectivityTrusted Source seems to occur 2 days prior to symptom onset to 3 days after symptom onset.
Rapid antigen tests can detect high viral loads and are currently thought to be reliable in telling people whether or not they could still be contagious.
Health officials recommend isolating for 5 to 10 days if you develop COVID-19. Infectious diseases specialists believe that, on average, the vast majority of people who contract the coronavirus are most contagious immediately before and immediately after symptoms appear.
ResearchTrusted Source shows that most people will no longer be contagious 5 to 6 days after symptoms appear.
Still, some evidence suggests about one-thirdTrusted Source of people who contract the infection continue to be infectious for a longer period.
Health experts do not recommend using a PCR test to determine if you may still be contagious since these types of tests are sensitive and can detect small amounts of non-infectious viruses.
Rapid antigen tests, on the other hand, can detect high viral loads and are currently thought to be more reliable in telling people whether or not they could still be contagious.
“For a symptomatic infection, the time from illness onset has been shown to be more reliable than PCR testing to predict the presence of live [or] contagious COVID-19 virus,” Dr. Charles Bailey, the medical director for infection prevention with Providence Mission Hospital and Providence St. Joseph Hospital in Orange County, CA, told Healthline.
“Antigen testing may be more capable of determining infectivity since its threshold for detecting COVID-19 more closely aligns with an amount of virus capable of transmission,” he added.
How long are people contagious? According to Bailey, the length of infectivity will vary from person to person and depends on the severity of infection, the intensity of exposure, and each person’s immune system.
In general, the window of highest infectivityTrusted Source seems to occur 2 days before symptom onset to 3 days after symptom onset. Contact tracing studiesTrusted Source from earlier in the pandemic have found that it’s less common for transmission to occur when exposed to a person 6 days after their symptom onset.
It’s still possible for people to transmit the virus to others after 5 days of symptoms, which is why health officials are advising people who recently recovered from their illness to continue wearing a mask for 5 days when they’re around other people.
One study recently published in the International Journal of Infectious Diseases found that about one-third of people with the infection continue to be contagious after 5 days. But it’s unclear if this remains true with the Omicron variant.