An infection of the nose, throat and lungs caused by a virus. Swine influenza is also called swine flu or H1N1.

In 2009, a new H1N1 virus partly of swine origin caused a human influenza pandemic. It was often called swine flu. That virus is one of the strains that cause seasonal flu. Influenza spreads through respiratory droplets. Most people with flu get better on their own. But flu and its complications can be deadly.

Symptoms are similar to those of other flu viruses. Symptoms may come on suddenly and include fever, muscle aches, chills and sweats, headache, tiredness, and runny or stuffy nose. Children also may have vomiting and diarrhea.

Treatment for influenza may include antiviral medicines. Treatment for symptoms includes drinking liquids, taking pain relievers you can get without a prescription for fever and headache, and resting. Seasonal flu vaccinations help prevent infection.