Asymptomatic Patients

There are currently few data as to whether individuals can be infected with the SARS virus but remain asymptomatic, and if so, whether asymptomatic persons can transmit infection.

Preliminary findings suggest that some individuals that only developed mild symptoms may have antibodies to the SARS virus, although they did not develop SARS. Seroconversion without any disease has also been documented.

There is no direct evidence of transmission from an asymptomatic person. Indirect evidence that it may occur rarely includes a report that contact tracing in Hong Kong failed to identify a known symptomatic SARS contact in a small percentage of reported cases (WHO, Update 53).