High morbidity and low mortality (1-4%). The virus is transmitted in swine herds by aerosols, direct and indirect contact, and by pigs carrying the virus asymptomatically. In temperate regions, interspecies outbreaks can occur throughout the year, but are more frequent in fall and winter. Many countries routinely vaccinate their swine herds against swine influenza.
Swine influenza viruses are most commonly of the H1N1 subtype, but other subtypes (e.g., H1N2, H3N1, H3N2) also exist. Like swine influenza viruses, pigs can also be infected with avian influenza viruses and human seasonal influenza viruses. It was initially thought that the H3N2 swine flu virus was transmitted from humans to pigs. Sometimes pigs can be infected with more than one virus type at a time, allowing the genes of these viruses to recombine or reassort. This can result in a single influenza virus containing genes from many sources, called a recombinant virus. In general, swine influenza viruses are species-specific and only infect pigs, but they do sometimes cross population barriers and cause disease in humans.
How is swine flu spread?
The spread of swine flu currently appears to be the same as that of the common flu. The virus is dispersed into the air by an infected person coughing or sneezing, and is then inhaled by those around them; or it attaches to surfaces of human contacts and then enters the mouth, eyes, and nose through the hands. It is possible for an infected person to infect others before symptoms appear, and the onset of infection usually occurs a week, or more, after infection. Children are contagious longer.
Swine flu: A respiratory infection caused by the swine flu virus, which causes flu-like symptoms in humans. It may occur through contact with infected hogs or exposure to an environment infected with the swine flu virus, or through contact with a person infected with the swine flu virus.
Swine flu symptoms: a sudden fever of 38 degrees or higher (100.4 degrees Fahrenheit), coughing, headache, joint pain, nasal congestion, generalized weakness, and lack of appetite. Some people infected with the virus also experience a runny nose, sore throat, nausea, vomiting as well as diarrhea. In some previously identified cases, swine flu has also been associated with pneumonia, respiratory failure, and chronic deterioration of health.
Unlike the human flu, a person infected with swine flu will have red eyes and severe body aches.