Coronavirus is most contagious before and during the first week of symptoms
As sweeping efforts to contain the COVID-19 pandemic go into effect around the globe, researchers are starting to get hints of just when patients are most contagious. People infected with the SARS-CoV-2 virus, which causes the disease, may test positive for the virus both before and after they have symptoms. But a new study of nine people who contracted the virus in Germany suggests that people are mainly contagious before they have symptoms and in the first week of the disease. Infectious viruses were isolated from about 17 percent of nose and throat swabs and more than 83 percent of phlegm samples during that first week, researchers report March 8 in a study posted at medRxiv.org. Patients produced thousands to millions of viruses in their noses and throats, about 1,000 times as much virus as produced in SARS patients, Clemens Wendtner, director of infectious disease and tropical medicine at Munich Clinic Schwabing, a teaching hospital, and his colleagues found. That heavy load of...