What is the difference between avian influenza, swine influenza and human influenza viruses?
Avian influenza viruses, swine influenza viruses, and human influenza viruses all belong to the same class of viruses known as Orthomyxoviruses. Avian influenza viruses circulate in wild and sometimes also domestic birds populations. Certain sub-types, including the highly pathogenic H5N1, are occasionally transmitted to mammals, including humans. Swine influenza viruses circulate in swine populations and are occasionally, albeit infrequently, transmitted to birds and to humans. Human influenza viruses circulate in human populations and are transmitted from person to person. Human influenza viruses are also transmissible to animals, pigs in particular. Pigs can therefore harbor viruses from avian and human sources, and act as “mixing vessels” for these viruses. An example of humans infecting pigs is the recent case reported by the Canadian Food Inspection Agency (CFIA) on 2 May 2009, announcing that it had found H1N1 flu virus in a swine herd in Alberta, and that it was highly probable
