Overview

Technically, the term "swine flu" refers to influenza in pigs. Occasionally, pigs transmit influenza viruses to people, mainly to hog farmers and veterinarians. Less often, someone infected with swine flu passes the infection to others.

The human respiratory infection caused by a particular influenza virus H1N1 strain — popularly known as swine flu — was first recognized in spring 2009. A few months after the first swine flu cases were reported, rates of confirmed H1N1-related illness were increasing in much of the world. As a result, the World Health Organization declared the infection a global pandemic.

The pandemic was declared over in August 2010. Currently, H1N1 is still circulating in humans as a seasonal flu virus and protection against this strain was included in the seasonal flu vaccine for 2015-16. Another strain, H3N2 emerged in humans in 2011.

Symptoms

H1N1 flu signs and symptoms in humans are similar to those of other flu strains:

  • Fever (but not always)
  • Cough
  • Sore throat
  • Runny or stuffy nose
  • Watery, red eyes
  • Body aches
  • Headache
  • Fatigue
  • Diarrhea
  • Nausea and vomiting

H1N1 flu symptoms develop about one to three days after you're exposed to the virus.

When to see a doctor

It's not necessary to see a doctor if you're generally healthy and develop flu signs and symptoms, such as fever, cough and body aches. Call your doctor, however, if you have flu symptoms and you're pregnant or you have a chronic disease, such as asthma, emphysema, diabetes or a heart condition, because you have a higher risk of complications from the flu.

Causes

Influenza viruses infect the cells lining your nose, throat and lungs. The virus enters your body when you inhale contaminated droplets or transfer live virus from a contaminated surface to your eyes, nose or mouth.

You can't catch swine flu from eating pork.

Risk factors

If you've traveled to an area where many people are affected by swine flu (H1N1 flu), you may have been exposed to the virus, particularly if you spent time in large crowds.

Swine farmers and veterinarians have the highest risk of true swine flu because of their exposure to pigs.

Complications

Influenza complications include:

  • Worsening of chronic conditions, such as heart disease and asthma
  • Pneumonia
  • Neurological signs and symptoms, ranging from confusion to seizures
  • Respiratory failure

Prevention

The Centers for Disease Control and Prevention recommends flu vaccination for all people older than 6 months of age. An H1N1 virus is one component of the seasonal flu shot for 2014-15. The flu shot also protects against two or three other influenza viruses that are expected to be the most common during the flu season.

The vaccine will be available as an injection or a nasal spray. The nasal spray is approved for use in healthy people 2 through 49 years of age who are not pregnant. The nasal spray isn't recommended for people who are older than 50, younger than 2, pregnant or allergic to eggs, or people who have asthma or a compromised immune system, or those who use aspirin therapy.

These measures also help prevent swine flu (H1N1 flu) and limit its spread:

  • Stay home if you're sick. If you have swine flu (H1N1 flu), you can give it to others. Stay home for at least 24 hours after your fever is gone.
  • Wash your hands thoroughly and frequently. Use soap and water, or if they're unavailable, use an alcohol-based hand sanitizer.
  • Contain your coughs and sneezes. Cover your mouth and nose when you sneeze or cough. To avoid contaminating your hands, cough or sneeze into a tissue or the inner crook of your elbow.
  • Avoid contact. Stay away from crowds if possible. And if you're at high risk of complications from the flu — for example, you're younger than 5 or you're 65 or older, you're pregnant, or you have a chronic medical condition such as asthma — consider avoiding swine barns at seasonal fairs and elsewhere.
  • Reduce exposure within your household. If a member of your household has swine flu, designate only one household member to be responsible for the ill person's personal care.

Swine flu (H1N1 flu) care at Mayo Clinic

Aug. 13, 2015
References
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