By Mayo Clinic Staff
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.
H1N1 flu signs and symptoms in humans are similar to those of other flu strains:
- Fever (but not always)
- Sore throat
- Runny or stuffy nose
- Watery, red eyes
- Body aches
- 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.
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.
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.
Influenza complications include:
- Worsening of chronic conditions, such as heart disease and asthma
- Neurological signs and symptoms, ranging from confusion to seizures
- Respiratory failure
Most cases of flu, including H1N1 flu, require only symptom relief. If you have a chronic respiratory disease, your doctor may prescribe additional medications to help relieve your symptoms.
The antiviral drugs oseltamivir (Tamiflu) and zanamivir (Relenza) are sometimes prescribed within the first day or two of symptoms to reduce the severity of your symptoms, and possibly the risk of complications. But, flu viruses can develop resistance to these drugs.
To make development of resistance less likely and maintain supplies of these drugs for those who need them most, antivirals are reserved for people at high risk of complications.
High-risk groups are those who:
- Are in a hospital, nursing home or other long-term care facility
- Are younger than 5 years of age, particularly children younger than 2 years
- Are 65 years and older
- Are pregnant or within two weeks of delivery, including women who have had pregnancy loss
- Are younger than 19 years of age and are receiving long-term aspirin therapy, because of an increased risk of developing Reye's syndrome, a rare but potentially fatal disease that can occur when using aspirin during a viral illness
- Are morbidly obese, defined as having a body mass index above 40
- Have certain chronic medical conditions, including asthma, emphysema, heart disease, diabetes, neuromuscular disease, or kidney, liver or blood disease
- Are immunosuppressed due to certain medications or HIV
- Are American Indians or Native Alaskans
If you develop any type of flu, these measures may help ease your symptoms:
- Drink plenty of liquids. Choose water, juice and warm soups to prevent dehydration.
- Rest. Get more sleep to help your immune system fight infection.
Consider pain relievers. Use an over-the-counter pain reliever, such as acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin IB, others), cautiously. Also, use caution when giving aspirin to children or teenagers.
Though aspirin is approved for use in children older than age 3, children and teenagers recovering from chickenpox or flu-like symptoms should never take aspirin. This is because aspirin has been linked to Reye's syndrome, a rare but potentially life-threatening condition, in such children.
Remember, pain relievers may make you more comfortable, but they won't make your symptoms go away faster and may have side effects. Ibuprofen may cause stomach pain, bleeding and ulcers. If taken for a long period or in higher than recommended doses, acetaminophen can be toxic to your liver.
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.
Aug. 13, 2015
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