High Quality Content by WIKIPEDIA articles! In March and April 2009, an outbreak of a new strain of influenza commonly referred to as "swine flu" infected many people in Mexico and other parts of the world, causing illness ranging from mild to severe. Initial reports suggested that the outbreak had started in February due to farming practices at a pig farm half-owned by Smithfield Foods. Smithfield Foods stated that it had found no clinical signs or symptoms of the presence of swine influenza in the company`s swine herd, or among its employees at its joint ventures in Mexico, that it routinely administers influenza virus vaccination to their swine herds and that it conducts monthly testing for the presence of swine influenza. The new strain was identified as a combination of several different strains of Influenzavirus A, subtype H1N1, including separate strains of this subtype circulating in humans and in pigs. The World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) have expressed serious concerns that the new strain, which transmits between humans and has had a relatively high mortality rate in the possible and confirmed Mexican cases, has the potential to become an influenza pandemic. It is reported that, because the virus is already widespread, containment will be impossible.