Swine influenza, or ‘swine flu’, is a highly contagious acute respiratory disease of pigs, caused by one of several swine influenza A viruses that cause regular outbreaks in pigs.
Outbreaks in pigs occur year round, with an increased incidence in autumn and winter in temperate zones. Many countries routinely vaccinate swine populations against swine influenza.
Swine influenza viruses are most commonly of the H1N1 subtype, but other subtypes are also circulating in pigs (e.g., H1N2, H3N1, H3N2). Pigs can also be infected with avian influenza viruses and human seasonal influenza viruses as well as swine influenza viruses.
The H3N2 swine virus was thought to have been originally introduced into pigs by humans.
Recent outbreak due to
Recent outbreak due to the new strain of influenza virus A (H1N1) has had cases reported from North America, Mexico, Spain and UK. Suspect cases have been reported from New Zealand and France and these are being investigated.