Coronavirus patients are no longer infectious after 11 days, according to a new study from the National Center for Infectious Diseases and the Academy of Medicine.
Researchers suggested that even if patients still test positive for COVID-19, they refrain from being infectious 11 days after developing the disease.
According to the joint paper, Singaporean infectious disease experts discovered that the virus “could not be isolated or cultured after day 11 of illness.”
The team investigated the “viral load” in 73 COVID-19 patients to determine whether the bug remained viable and could further spread.
“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 could still get positive results of the coronavirus test after two weeks. However, tests could be acquiring fragments of the virus that can no longer spread 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 added.
According to the researchers, the study’s findings could help hospitals make decisions about when to discharge patients.
Many hospitals in the US require patients test negative for the virus twice for them to be categorized as recovered ones from COVID-19.
The sample size in the study was small, but researchers believe that their observations will become a basis of 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.
In terms of manifesting coronavirus symptoms, another study, published in the journal Annals of Internal Medicine, affirmed that people with the symptoms of COVID-19 may only experience them five days after their exposure to the virus.
The study “The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application” discovered that people would manifest coronavirus symptoms 5.1 days after their initial exposure. It was the median length as incubation periods vary. Some people show signs of illness within two weeks.
“Based on our analysis of publicly available data, the current recommendation of 14 days for active monitoring or quarantine is reasonable, although with that period some cases would be missed over the long term,” said Justin Lessler of the Johns Hopkins Bloomberg School of Public Health and senior author of the report.
Lessler’s team reported that for 98% of people who acquire symptoms of COVID-19, the transmission of the virus can take place within 11.5 days of exposure. The researchers suggest that for every 10,000 individuals quarantined for 14 days, only 101 would manifest symptoms upon release from quarantine.
Graham Cooke, professor of infectious diseases at Imperial College London, pointed out that people must not treat the findings as a clear bill of health if no signs of illness show up within five days of a potential exposure. “That’s absolutely the wrong interpretation,” he said. “At five days, half of people won’t yet have developed symptoms.”