b'Swine FluWhat is it? of swine flu were reported in the US. By Swine influenza is a common respiratoryApril, 900 cases of suspected swine flu were illness in pigs caused by a strain of influenzareported in Mexico and two months later, a A virus. The H1N1 strain responsible forpandemic was declared 189 . It is said to have the 2009 outbreak had been circulatingstarted in La Gloria, Mexico, just five miles undetected in the swine populationfrom a major concentration of large-scale for several years prior to its emergencepig factory farms 190 .in humans, causing only subclinical symptoms 185 .Despite the popular nameIn all, 457 people in the UK died between swine flu the virus is made up of geneticApril 2009 and March 2010 in a pandemic segments originating from avian, swinethat cost the country 1.24 billion 191 . and human strains. In this case, the pigWorldwide, the pandemic is estimated to had acted as a mixing vessel for the virus tohave killed between 151,700 and 575,400 change its genetic form 186 . people 192 . HistoryToday, this strain of influenza is not usually specifically tested for and it has joined the H1N1 swine flu is a descendant of the avianset of seasonal flu viruses that circulate flu that killed at least 50 million people ineach winter 193 .the 1918 epidemic. After 1919, the virus continued to circulate and caused seasonal outbreaks in both people and pigs 187 . TheRoutes of transmissionvirus was first confirmed in pigs in 1931 andInfluenza viruses can be transmitted in 1976, an H1N1 virus jumped from pigsbetween pigs, from pigs to people, from to people, killing one person in the US. Bypeople to pigs, and between people 194 . 1977, it was circulating in people in China.Pigs can be infected by avian influenza and human influenza viruses as well as swine In 1998, the first hybrid virus - madeinfluenza viruses. When influenza viruses from human, bird and pig viruses - wasfrom different species infect pigs, the discovered in a North Carolina factory farm.viruses can recombine and new viruses that It spread rapidly. Vaccines could not controlare a mix of pig, bird and human viruses can it because the virus kept evolving 188 . emerge.In March 2009, the first cases of a new typeThe virus is transmitted in the same way as seasonal flu, through tiny droplets emitted 28'