Suspected case was defined as individual who travelled to, or resided in, Wuhan or any nearby city within 14 days before symptom onset; hand contact history with an individual with a RT-PCR confirmed COVID-19 test within 14 days of symptom onset; had contact history with a patient experiencing fever or other respiratory symptoms and come from Wuhan or any community with reported COVID-19 cases within 14 days of before symptoms onset; or was related with a known COVID-19 cluster; and had two or more signs and symptoms.

A confirmed case was an individual with a laboratory confirmed COVID-19 infection.

Imported cases were defined as persons that resided in or had travelled to the Hubei province within 2 weeks before symptom onset. All other cases were designated as local cases.

For those considered asymptomatic cases, primary or secondary case status was determined by collection dates of the earliest SARS-CoV-2 positive specimens.