Outbreak of Influenza A (H3N2) Variant Virus Infection among Attendees of an Agricultural Fair, Pennsylvania, USA, 2011

摘要

During August 2011, in. uenza A (H3N2) variant [A(H3N2)v] virus infection developed in a child who at-tended an agricultural fair in Pennsylvania, USA; the virus resulted from reassortment of a swine in. uenza virus with in. uenza A(H1N1)pdm09. We interviewed fair attendees and conducted a retrospective cohort study among mem-bers of an agricultural club who attended the fair. Proba-ble and confi rmed cases of A(H3N2)v virus infection were defi ned by serology and genomic sequencing results, re-spectively. We identifi ed 82 suspected, 4 probable, and 3 confi rmed case-patients who attended the fair. Among 127 cohort study members, the risk for suspected case status increased as swine exposure increased from none (4%; ref-erent) to visiting swine exhibits (8%; relative risk 2.1; 95% CI 0.2–53.4) to touching swine (16%; relative risk 4.4; 95% CI 0.8–116.3). Fairs may be venues for zoonotic transmis-sion of viruses with epidemic potential; thus, health offi cials should investigate respiratory illness outbreaks associated with agricultural events