Influenza A virus has a wide host range, which facilitates rapid viral evolution and has produced a diverse pool of influenza viruses worldwide. Pigs can be infected with human, swine and avian origin influenza A viruses, and infection in swine typically causes respiratory disease characterized by fever, cough, nasal discharge, and fatigue. When pigs and people are in close contact, influenza A viruses can spread between the two species, which is one way new influenza pandemics can be generated. When a person becomes infected with a swine origin influenza A virus it is termed a variant virus infection and denoted with a "v" after the subtype (e.g. H3N2v). This transmission between species has happened periodically, but swine-to-human transmission has been documented most frequently at swine exhibitions during agricultural fairs.
Agricultural fairs are educational settings across North America where pigs are exhibited by youth learning about agriculture, animal husbandry, and food production. Agricultural fairs differ from commercial swine production facilities because they create lengthy periods of commingling multi-source pigs with millions of people. While exhibition pigs represent a very small part of the overall swine industry, they are the most common way for the public to interface with pigs and their pathogens.
In the past 5 years, cases of influenza A H1N1v, H1N2v, and H3N2v have all been associated with swine exhibitions. In 2012 there were a total of 309 cases of H3N2v identified in 12 states with the majority of the cases being swine exhibitors at agricultural fairs (Bliss, et al., 2016). Despite mitigation efforts, variant influenza virus infections continue to occur. Most recently, 18 people became ill during 2016 after attending fairs in Michigan and Ohio (Schicker, R.S., et al., 2016). Most healthy individuals recover from influenza infections with no difficulties; however, influenza complications are more likely for children younger than 5 years of age, people 65 years of age and older, pregnant women, and people with certain long-term health conditions (CDC, 2016).
In a 3-year survey of fairs in the Midwest United States, 23% of fairs had influenza-infected pigs (Killian, M.L., et al., 2012). Many fairs are weeklong events with animals on display for the duration of the fair, which gives ample time for the virus to spread among the pigs. Typically, less than 1.5% of pigs arrive at a fair with influenza, but these few infected pigs are able to spread the virus to nearly all the other pigs by the end of the fair (Bliss, et al., 2016; Killian, et al., 2012). One recommendation aimed at minimizing influenza transmission at fairs is to limit the time pigs are on the fairgrounds to 72 hours (Bowman et al., 2014). Additionally, public health officials recommended people wash their hands with soap and running water before and after exposure to animals. Eating and drinking should not occur in animal areas, and attendees should refrain from bringing pacifiers, sipping cups, or strollers into animal areas. A veterinarian should be contacted if pigs are suspected to be sick and people should avoid close contact with animals that look or act ill.
Since exhibitions allow for viral transmission, producers should take care to protect non-exhibition swine at home. As an example, exhibition pigs should be isolated from herd mates and observed for clinical signs of influenza for at least seven days after an exhibition to prevent transmission to pigs that did not attend the fair. Additionally, equipment, clothing, shoes, and vehicles/trailers should be cleaned and disinfected before and after exhibitions (Bowman et al., 2014).
Agricultural fairs are valuable settings for youth and the public to learn about agriculture and food production systems. The risk of catching influenza from pigs at a fair can be reduced by following good hygiene practices, avoiding noticeably sick animals, and reducing the time pigs are comingled together. Fairs are a celebration of culture and an anticipated socializing event in many communities, but it is important that people at risk for complications from influenza infection are aware of the possible health risks.