Coronavirus patients stop being infectious 11 days after contracting the disease — even if they still test positive for COVID-19 on day 12, according to a new study.
Singaporean infectious disease experts said they found that the virus “could not be isolated or cultured after day 11 of illness,” according to a joint paper from the country’s National Center for Infectious Diseases and the Academy of Medicine.
Researchers looked at the “viral load” in 73 COVID-19 patients to measure whether the bug was still viable and could infect anyone.
“Based on the accumulated data since the start of the COVID-19 pandemic, the infectious period of [coronavirus] in symptomatic individuals may begin around 2 days before the onset of symptoms, and persists for about 7-10 days after the onset of symptoms,” the researchers wrote.
Patients may still test positive after two weeks, but tests could be picking up fragments of the virus that are no longer viable for spreading the infection, researchers said.
“Active viral replication drops quickly after the first week, and viable virus was not found after the second week of illness,” researchers wrote.
The researchers suggested that the findings could inform hospitals’ decisions about when to discharge patients.
In the US, many hospitals require patients test negative for the virus twice to be considered recovered from COVID-19.
Though the sample size was small, researchers are confident that their findings will be replicated in larger studies, NCID executive director Leo Yee-Sin told Singaporean newspaper the Strait Times.
“Scientifically, I’m very confident that there is enough evidence that the person is no longer infectious after 11 days,” she said.
