What Is Swine Flu (H1N1)?
By Kristina Duda, RN Medically reviewed by Andy Miller, MD Updated on March 23, 2020
In This Article
History
Symptoms
Causes
Diagnosis
Treatment
Swine flu is the name for the influenza type A virus that affects pigs (swine). Although swine flu doesn't typically affect humans, there was a global outbreak (pandemic) in 2009 to 2010—the first flu pandemic in more than 40 years. It was caused by a then-new flu virus known as H1N1, an influenza virus that's a combination of swine, avian (bird), and human genes that mixed together in pigs and spread to humans.1 H1N1 is now considered a normal type of seasonal flu and is included in the flu vaccine.
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History
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.
The Centers for Disease Control and Prevention (CDC) estimates that swine flu infected nearly 61 million people in the United States and caused 12,469 deaths.2 Worldwide, up to 575,400 people died from pandemic swine flu.3
The 1918 influenza pandemic was also caused by an H1N1 virus. Known as the Spanish flu, its genes show that it may have developed from a swine flu virus or from an avian (bird) flu virus. The pandemic killed an estimated 50 million people worldwide and was notable in that it had a high death rate among healthy adults.4
Swine Flu Symptoms
H1N1 causes respiratory illness and is very contagious.1 Symptoms of H1N1 are similar to those of the seasonal flu and may include:
Fever
Body aches5
Loss of appetite
Cough
Sore throat5
Headache
Fatigue
Runny nose
Irritated eyes
Vomiting, nausea
Diarrhea5
Signs and Symptoms of Swine Flu
Causes
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 2010.6
Pigs are able to contract all three types of influenza (human, swine, and avian), make them perfect vessels in which the virus can mix and change. The H1N1 virus is made of swine, human, and avian genes that metamorphosed in pigs, probably several years before the pandemic (hence the name "swine flu.")
Influenza circulates among pigs throughout the year but is most common during the late fall and winter, similar to the human flu season. Sometimes pigs can pass the flu to the humans who work.1 This is what happened during the 2009 to 2010 pandemic, only, in this case, the new H1N1 strain spread quickly because humans had no immunity to it.
When people get the H1N1 virus, it's in the same way they can get any type of flu— by contact with another person who is sick, from either droplets in the air that contain the live virus or by touching a surface that has been contaminated and then touching your eyes, nose, or mouth.
You can't get influenza from eating pork, though you should always make sure that it's cooked thoroughly and handled carefully.
Causes and Risk Factors of Swine Flu
Diagnosis
If you develop signs of the flu and are otherwise in good health, you likely don't need to see a doctor. However, if you're pregnant, your immune system is compromised, or you have a chronic illness such as asthma, diabetes, emphysema, or a heart condition, you should see your doctor right away.7
Your doctor will be able to diagnose you with the flu by taking a swab from your nose and/or throat within the first four to five days of your sickness. There are rapid influenza diagnostic tests that can tell if you have the flu or not, as well as which type (A or B), though they are not as accurate as other
