WASHINGTON - The U.S. Centers for Disease Control and Prevention has updated its guidance on how long most people in the U.S. should isolate after testing positive for COVID-19.
In guidance posted online, the agency states that available information on the infectiousness of the virus indicates that most adults with mild to moderate cases of COVID-19 remain infectious “no longer than 10 days” after the date on which their symptoms first began.
Instead of a 14-day quarantine window, the CDC now recommends 10 days after the onset of symptoms and 24 hours after a fever has broken.
“For most persons with COVID-19 illness, isolation and precautions can generally be discontinued 10 days after symptom onset and resolution of fever for at least 24 hours, without the use of fever-reducing medications, and with improvement of other symptoms,” the agency states.
But the CDC noted that “a limited number of persons with severe illness” may continue to transmit the virus beyond 10 days and need to isolate for a longer period — possibly for up to 20 days after symptom onset.
Since the novel coronavirus first emerged six months ago, researchers have been racing to better understand the virus and how it’s transmitted. People are thought to be the most contagious early in the course of their infection.
“One of the main problems with general rules regarding contagion and transmission of this coronavirus is the marked differences in how it behaves in different individuals. That's why everyone needs to wear a mask and keep a physical distance of at least six feet,” Harvard Health explains on its website.
The CDC also added that research indicates that people infected with a related but separate human coronavirus may become susceptible to the illness approximately 90 days after illness onset.
“For persons recovered from SARS-CoV-2 infection, a positive PCR during the 90 days after illness onset more likely represents persistent shedding of viral RNA than reinfection,” the CDC wrote.
As for the time frame during which an individual can be infectious, medical experts have issued similar recommendations that fall in line with the new CDC guidelines.
Julian Tang, a virologist with the University of Leicester in the United Kingdom and the National University of Singapore, told the Washington Post that he has advised clinical teams that patients can be released from isolation after 10 days.
“You’re not going to reach absolute zero risk,” Tang said, “but the studies have shown viral shedding mostly stops after 10 days,” he said.
A research paper published in March in the journal Nature found that antibodies were actually able to neutralize the virus approximately five days into the initial onset of infection. No live virus was detected by the eighth or ninth day, according to researchers.
While findings like these are promising, the CDC added that “even for pathogens for which many years of data are available, it may not be possible to establish recommendations that ensure 100% of persons who are shedding replication-competent virus remain isolated.”
As more is learned about the novel coronavirus, the CDC said it will monitor updates and provide additional information that would “warrant reconsideration of these recommendations.”
This story was reported from Cincinnati and Los Angeles.