Persons that want to get the full benefit from home quarantine should isolate themselves for a full 14 days.
The U.S. Centers for Disease Control and Prevention says this length is optimal after exposure to a person with the disease, even as it now reveals shorter quarantine periods are acceptable but based on test results and symptoms.
On Wednesday, CDC said quarantine can end after only 10 days if a person hasn't developed any symptoms. Quarantine can also end after just seven days if the asymptomatic person also tests negative for the virus.
The sample for the negative test should be collected within 48 hours of the final day of quarantine, according to CDC.
"We continue to refine our guidance to prevent transmission and protect Americans," said Dr. Henry Walke, CDC COVID-19 incident manager.
"Reducing the length of quarantine may make it easier for people to follow critical public health action by reducing the economic hardship associated with a longer period, especially if they cannot work during that time."
Walke said local health officials can adjust CDC's recommendations to fit situations in their jurisdictions. He said people should monitor their own symptoms for a full 14 days after an exposure regardless of the length of quarantine.
The three recommended quarantine periods apply to persons deemed "close contacts" of COVID-19 patients. CDC defines a close contact as "someone who was within 6 feet of an infected person for a cumulative total of 15 minutes or more over a 24-hour period starting from two days before illness onset." A close contact is also a person with a positive test result.
CDC said the rationale for announcing the shorter quarantine options was also based on attaining more compliance among the American public. CDC has received reports from local public health departments of people exiting quarantine too early after an exposure.
Existing CDC guidance recommends anyone exposed to the coronavirus must quarantine for 14 days. Walke said CDC still recommends a 14-day quarantine "as the best way to reduce the risk of spreading Covid-19." On the other hand, Walke said CDC has identified "two acceptable alternatives," which are the 10-day and seven-day quarantine periods.
Ending quarantine after 10 days without a negative test leads to about 1% risk of spreading the virus to others, based on modeling by CDC and outside researchers.
After a seven-day quarantine with a negative test, there's about a 5% chance of spreading the virus, said Dr. John Brooks, Chief Medical Officer for CDC's COVID-19 response.
"In a situation where cases are rising that means that the number of contacts is rising, and the number of people who require quarantine is rising," said Brooks.
"That's a lot of burden, not just on the people who have to quarantine, but also on public health. We believe that if we can reduce the burden a little bit, accepting that it comes at a small cost, we make greater compliance overall with people."
The change to the quarantine guidelines received praise from epidemiologists and public health experts.
Dr. Bill Schaffner, an epidemiologist at Vanderbilt University, said the new quarantine guidelines will help potentially exposed people return to work more quickly.
"This is good for public health and good for the economy," he said, "and good for people's mental health."
He also said public health specialists have been awaiting the change with "delghted anticipation."
Schaffner explained the 14-day recommendation "was written before testing was widely available." Researchers have since learned more about the coronavirus.
"Several of us have thought for some time that now that testing is available you could introduce that into the scheme of how to evaluate people who are in quarantine," he said.
