Covid-19 patients are no longer infectious after 11 days of getting sick even though some may still test positive, according to a new study by infectious disease experts in Singapore.

A positive test “does not equate to infectiousness or viable virus,” a joint research paper by Singapore’s National Centre for Infectious Diseases and the Academy of Medicine, Singapore said. The virus “could not be isolated or cultured after day 11 of illness.”

The paper was based on a study of 73 patents in the city-state.

The latest findings may have implications on the country’s patient discharge policy. The discharge criteria is currently based on negative test results rather than infectiousness.

Singapore’s strategy on managing Covid-19 patients is guided by the latest local and international clinical scientific evidence, and the Ministry of Health will evaluate if the latest evidence can be incorporated into its patient clinical management plan, according to a report by the Straits Times.

So far, 13,882, or about 45% of the total 31,068 Covid-19 patients in Singapore have been discharged from hospitals and community facilities. Singapore reported 642 new Covid-19 cases as of noon on Saturday.

The government has been actively screening pre-school staff as it prepares to reopen pre-schools from June 2. On Friday, two pre-school employees tested positive for the novel coronavirus, bringing the total number of confirmed cases among pre-school staff to seven, according to the Ministry of Health.