Swine flu is a type of influenza, or flu, often found in pigs that occasionally causes outbreaks of disease in people. Health agencies typically record a few cases of swine flu in human beings every year. Until 2009, however, larger outbreaks of the disease had not occurred. In 2009, an outbreak of swine flu spread to several countries and caused over 200,000 deaths. In June of that year, the World Health Organization (WHO) declared that the swine flu outbreak had become a global pandemic (extremely widespread occurrence). However, WHO officials noted that the virus was not causing more severe illness or an unusual number of deaths.
The swine flu is caused by a strain of a virus known as H1N1, a common subtype of type A influenza. This variety of flu infects typically animals, including swine, and is occasionally transmitted to human beings. Symptoms of infection include fever, headache, cough, sore throat, and other signs of disease found in other varieties of flu.
Scientists first identified the H1N1 flu virus in swine in 1930. In 1976, an outbreak of swine flu at a United States Army base killed one person. At that time, U.S. President Gerald R. Ford ordered a nationwide immunization program to prevent a possible pandemic. However, the 1976 outbreak did not become widespread as health experts had feared. In addition, some people had serious reactions to the swine flu vaccine.
The virus that caused the 2009 outbreak was a previously unknown strain—a combination of avian (bird), swine, and human influenza viruses. Medical experts think that the outbreak began in Mexico. Unlike other strains of swine flu, this strain passed readily from person to person through close contact. The virus quickly spread to other countries in the Americas, Europe, and Asia.
See also Influenza .
