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When is someone infectious?

The onset and duration of viral shedding and period of infectiousness for COVID-19 are not yet conclusively known; however, early evidence indicates that people are likely most infectious right after contracting the virus, possibly before knowing they're sick.

It is possible that SARS-CoV-2 RNA may be detectable in the upper or lower respiratory tract for weeks after illness onset, similar to infection with MERS-CoV and SARS-CoV. However, detection of viral RNA does not necessarily mean that infectious virus is present. Asymptomatic infection with SARS-CoV-2 has been reported, but it is not yet known what role asymptomatic infection plays in transmission. Similarly, the role of pre-symptomatic transmission (infection detection during the incubation period prior to illness onset) is unknown. Existing literature regarding SARS-CoV-2 and other coronaviruses (e.g. MERS-CoV, SARS-CoV) suggest that the incubation period may range from 2--14 days.

Source: Centers for Disease Control and Prevention

Drafted 14 April 2020