Coronavirus can spread one to three days before symptoms appear - CDC

People infected with the novel coronavirus can transmit the infection one-to-three days before symptoms start to appear, according to a study published by the U.S. Centers for Disease Control and Prevention (CDC).

The study looked at 243 cases of COVID-19, the illness caused by the coronavirus, reported in Singapore between January 23 to March 16 and identified seven "clusters" where pre-symptomatic transmission was likely.

In four such groups, where the date of exposure could be determined, pre-symptomatic transmission occurred one-to-three days before symptoms started showing in the source patient, researchers said.

The findings from the study suggest that it might not be enough for people showing symptoms to limit their contact with others to control the pandemic, the researchers wrote in the CDC's Morbidity and Mortality Weekly Report, which was published online on Wednesday.

The CDC data adds to previous reports of individual cases in China that indicated the virus could spread before symptoms start to appear, while highlighting the importance of social distancing to fight the coronavirus outbreak.