The Centers for Disease Control and Prevention said Monday that people who test positive for Covid-19 but have no symptoms should isolate for five days, down from the previous recommendation of 10 days.
The agency attributed the change to growing evidence that the virus is most infectious in the two or three days after symptoms arise.
In addition to cutting the time in half for isolation, the CDC said that for people who are asymptomatic, an additional five days of wearing a mask when around others is recommended.
"Therefore, people who test positive should isolate for five days and, if asymptomatic at that time, they may leave isolation if they can continue to mask for five days to minimize the risk of infecting others," the CDC said in a statement.
The agency also recommended that unvaccinated people or those who are more than six months out from their second mRNA dose and not yet boosted should quarantine for five days after exposure to the virus followed by "strict mask use for an additional 5 days."
“The Omicron variant is spreading quickly and has the potential to impact all facets of our society. CDC’s updated recommendations for isolation and quarantine balance what we know about the spread of the virus and the protection provided by vaccination and booster doses," CDC Director Rochelle Walensky said in a statement.
"These updates ensure people can safely continue their daily lives. Prevention is our best option: get vaccinated, get boosted, wear a mask in public indoor settings in areas of substantial and high community transmission, and take a test before you gather,” she added.
The revised guidance comes as the U.S. sees a surge in Covid cases due in large part to the highly contagious omicron variant.
Dr. Anthony Fauci, President Joe Biden's chief medical adviser, told NBC Nightly News that the new guidance takes into account both public health data and worker shortages.
"You have so many people simultaneously testing positive you want to make sure that, particularly among essential workers, that you get people out there much sooner," he said. "So you can keep people safe from getting infected from you, if you still are infected, but at the same time getting you back to what might be an essential function in society."
Fauci added, "On balance, if you look at the safety of the public, and the need to have society not disrupted, this was a good choice."
Last week, the CDC recommended a shortened isolation times for health care workers who test positive but are asymptomatic. The agency said health care workers can return to work after seven days and a negative test, adding that “isolation time can be cut further if there are staffing shortages." Health care workers who have received both vaccine doses, including a booster, do not need to quarantine following a high-risk exposure, the CDC said.
Some states have also eased their isolation requirements for essential workers. Gov. Kathy Hochul announced last week that New York, which has seen a record-breaking surge of cases, is shortening the isolation window to five days for frontline workers to address staffing concerns at businesses.