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Contact history analysis of the 176 confirmed cases. (A) The contact history was obtained by patients or family members, and the duration spanned 14 days before symptom onset. Stars indicate the 12 cases after contact with infected asymptomatic carriers. (B) Twelve patients (primary infection, PI) infected by asymptomatic carriers (AC) from Wuhan; the secondary infections (SI) were surveyed. Eleven asymptomatic infections caused 12 primary infections and four secondary infections.
