A total of 18 human outbreaks with influenza A (H3N2) virus occurred in 2016 after individuals were exposed to influenza-infected swine at 7 agricultural fairs in Ohio and Michigan, according to a report published in Emerging Infectious Diseases.

Outbreaks of H3N2 virus were reported in Ohio and Michigan between July and August 2016, and all persons identified with the virus reported swine exposure while attending a fair in these states. Andrew S. Bowman, MS, PhD, from the Ohio State University in Columbus, and colleagues sought to identify whether the role of exhibition swine caused the human outbreak of H3N2.

Active influenza A virus surveillance among exhibition swine occurred during the summer of 2016 at 101 agricultural fairs across the Midwestern US. Pigs were sampled at the end of each exhibition, irrespective of clinical signs of respiratory disease. Nasal swabs or wipes were obtained from swine and screened for the influenza A virus.

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The researchers found that 4 fairs in Ohio and 4 in Michigan were associated with H3N2 cases. A total of 161 pigs were sampled across the 7 fairs, and the average prevalence of influenza-A swine in these fairs was 77.5%.  The viruses found in pigs were nearly identical to those found in the humans, the researchers said.  The compatibility and the wide dispersal of the H3N2 virus suggest the need for vigilance, they added.

“In addition to the zoonotic risks of influenza A virus, this pattern serves as a warning of possible dissemination of other emerging or high-consequence diseases in swine,” Dr Bowman and his colleagues concluded.


  1. Bowman AS, Walia RR, Nolting JM, et al.  Influenza A(H3N2) Virus in Swine at Agricultural Fairs and Transmission to Humans, Michigan and Ohio, USA, 2016.  Emerg Infect Dis. 2017;23(9):1551-1555.  doi: 10.3201/eid2309.170847