The US Centres for Disease Control and Prevention (CDC) has updated its guidelines for testing people who do not show symptoms of the novel Coronavirus. "Due to the significance of asymptomatic and pre-symptomatic transmission, this guidance further reinforces the need to test asymptomatic persons, including close contacts of a person with documented SARS-CoV-2 infection," the CDC said on its website on Friday.

"Testing is recommended for all close contacts of persons with SARS-CoV-2 infection. Because of the potential for asymptomatic and pre-symptomatic transmission, it is important that contacts of individuals with SARS-CoV-2 infection be quickly identified and tested," it added. It is a change from the CDC guidance released last month, which said testing might not be necessary for people without symptoms.