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.

In the spring of 2009, scientists recognized a particular strain of flu virus known as H1N1. This virus is actually a combination of viruses from pigs, birds and humans. During the 2009-10 flu season, H1N1 caused the respiratory infection in humans that was commonly referred to as swine flu. Because so many people around the world got sick that year, the World Health Organization declared the flu caused by H1N1 to be a global pandemic.

In August 2010, the World Health Organization declared the pandemic over. Since that time, scientists have changed the way they name viruses. The H1N1 virus is now known as H1N1v. The v stands for variant and indicates that the virus normally circulates in animals but has been detected in humans. Since 2011, another strain, H3N2v, has been circulating in humans and also causes the flu. Both strains are included in the flu vaccine for 2018-19.

Symptoms

The signs and symptoms of swine flu are similar to those of infections caused by other flu strains and can include:

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

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 that line 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 lived in or traveled to an area where many people are affected by swine flu, you may have been exposed to the virus.

Swine farmers and veterinarians have the highest risk of exposure to true swine flu because they work with and are near 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 annual flu vaccination for everyone age 6 months or older. Flu vaccines for 2018-19 protect against the viruses that cause swine flu and one or two other viruses that are expected to be the most common during flu season.

The vaccine is 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 some groups, such as pregnant women, children between 2 and 4 years old with asthma or wheezing, and people who have compromised immune systems.

These measures also help prevent flu and limit its spread:

  • Stay home if you're sick. If you have the 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. Wear a face mask if you have one. 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.

Swine flu (H1N1 flu) care at Mayo Clinic

Jan. 10, 2019
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