Viral shedding dropped after day 5 in all but two of the patients, who had more serious illness. The researchers found very high levels of virus emitted from the throat of patients from the earliest point in their illness -when people are generally still going about their daily routines. That type of test can indicate whether a patient is still shedding viral debris, but cannot indicate whether the person is still infectious. Those tests are conducted using PCR - polymerase chain reaction - which looks for tiny sections of the RNA of the virus. In some cases, people test positive for weeks after recovery, the World Health Organization has noted. Public health officials and hospitals have been trying to make sense of patients who seem to have recovered from Covid-19 but who still test positive for the virus based in throat swabs and sputum samples. “Based on the present findings, early discharge with ensuing home isolation could be chosen for patients who are beyond day 10 of symptoms with less than 100,000 viral RNA copies per ml of sputum,” the authors said, suggesting that at that point “there is little residual risk of infectivity, based on cell culture.” Importantly, the scientists could not grow viruses from throat swabs or sputum specimens after day 8 of illness from people who had mild infections. The latter type of testing - trying to grow viruses - is critical in the quest to determine how people infect one another and how long an infected person poses a risk to others. In addition to tests looking for fragments of the virus’s RNA, they also tried to grow viruses from sputum, blood, urine, and stool samples taken from the patients. The researchers monitored the viral shedding of nine people infected with the virus. Exclusive analysis of biotech, pharma, and the life sciences Learn More

Viral infections durations