Learn About H1N1 Influenza
The H1N1 virus (swine flu) is an infection of the nose, throat, and lungs. It is caused by the H1N1 influenza virus.
Swine flu; H1N1 type A influenza
Earlier forms of the H1N1 virus were found in pigs (swine). Over time, the virus changed (mutated) and infected humans. H1N1 is a new virus first detected in humans in 2009. It spread quickly around the world.
The H1N1 virus is now considered a regular flu virus. It is one of the three viruses included in the regular (seasonal) flu vaccine.
You cannot get H1N1 flu virus from eating pork or any other food, drinking water, swimming in pools, or using hot tubs or saunas.
Any flu virus can spread from person to person when:
- Someone with the flu coughs or sneezes into air that others breathe in.
- Someone touches a doorknob, desk, computer, or counter with the flu virus on it and then touches their mouth, eyes, or nose.
- Someone touches mucus while taking care of a child or adult who is ill with the flu.
Symptoms, diagnosis, and treatment of H1N1 influenza are similar to that for the flu in general.
Benjamin Cowling practices in Sar, China. Mr. Cowling is rated as an Elite expert by MediFind in the treatment of H1N1 Influenza. His top areas of expertise are Flu, Avian Influenza, H1N1 Influenza, Thyroidectomy, and Hormone Replacement Therapy (HRT).
Natasha Crowcroft practices in Toronto, Canada. Ms. Crowcroft is rated as an Elite expert by MediFind in the treatment of H1N1 Influenza. Her top areas of expertise are Measles, Parainfluenza, H1N1 Influenza, and Pertussis.
Walter Haas practices in Berlin, Germany. Mr. Haas is rated as an Elite expert by MediFind in the treatment of H1N1 Influenza. His top areas of expertise are H1N1 Influenza, Flu, Severe Acute Respiratory Syndrome (SARS), and Pulmonary Tuberculosis.
Published Date: April 01, 2025
Published By: Linda J. Vorvick, MD, Clinical Professor Emeritus, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
Centers for Disease Control and Prevention website. About swine/variant flu. www.cdc.gov/swine-flu/about/index.html. Updated July 8, 2024. Accessed July 6, 2025.
Treanor JJ. Influenza viruses, including avian influenza and swine influenza. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 165.