Swine flu is an infection caused by a virus. It's named for a virus that pigs can get. People do not normally get swine flu, but human infections can and do happen. In 2009 a strain of swine flu called H1N1 infected many people around the world. The virus is contagious and can spread from human to human.
H1N1 was first detected in April 2009 in a 10-year-old girl in California. It was declared a global pandemic in June 2009 by the World Health Organization (WHO) and was finally over in August 2010.
H1N1 causes a respiratory illness and is very contagious. Symptoms of H1N1 are similar to those of the seasonal flu and may include:
Loss of appetite
A sore throat
A runny nose
Vomiting, nausea, and diarrhea
Type A influenza viruses have the ability to mix with other strains, creating a new strain, which is what happened to cause the pandemic of 2009 to 2010. Pigs are able to contract all three types of influenza (human, swine, and avian), creating a place for the virus to mix and change. The H1N1 virus is a type A virus with swine, human, and avian genes that metamorphosed in pigs, probably several years before the pandemic, and was named "swine flu" because it was thought to be similar to the viruses known to infect pigs.
Influenza circulates among pigs throughout the year but is most common during the late fall and winter, similar to the human flu season.
H1N1 flu is a virus just like any other strain of flu, but it does appear to respond to the antiviral medications Tamiflu and Relenza. These medications do not cure the illness, but they may shorten the duration, make symptoms less severe, or help you avoid it altogether if you are exposed. They are usually reserved for people who are at a higher risk of complications, so the likelihood of the virus developing a resistance to them is lessened.
Otherwise, treatment for most people mainly consists of comfort measures and treating symptoms as they occur. If you have asthma or emphysema, for instance, your doctor might add a medication to help relieve your respiratory symptoms.