Swine influenza

Definition

Swine influenza is flu infection found in pigs. The virus that causes this infection in pigs can change (mutate) to become infectious to humans. The disease is of concern to humans, who may have no immunity against it. This mutation could start a worldwide epidemic.
Alternative Names
Swine flu
H1N1 flu

Causes

In the spring of 2009, cases of human infection with swine flu were confirmed in Mexico and in several states in the United States. Cases of infection in humans were also reported in other countries.

The most well known outbreak of swine flu occurred among soldiers in Fort Dix, New Jersey, in 1976. The virus caused disease and pneumonia in at least 4 soldiers and 1 death. All of the infected soldiers lived in close contact. The virus is thought to have circulated for a month and disappeared. The source of the virus, when it was introduced to Fort Dix, and the reasons why it did not spread more are unknown. Until now, very few cases of swine flu had been reported since.

The swine flu virus is contagious and can spread from human to human. At this time, it is unknown how easily it can spread between people.

It is known that flu viruses can spread from pigs to people, and from people to pigs. However, you CANNOT get the swine flu virus from eating pork.

Human-to-human infection with the swine flu virus likely occurs the same way as seasonal flu, when an infected person coughs or sneezes into air that others breathe in. People may also get infected by touching something with the virus on it, such as a door knob or counter, and then touching their mouth or nose.

You can find an updated case count of confirmed swine flu infections in the U.S. at the Centers for Disease Control and Prevention (CDC) web site.

Symptoms

Symptoms of swine flu infection in humans are similar to classic flu-like symptoms, which might include:

• Fever above 100.4 °F
• Cough
• Sore throat
• Headache
• Chills
• Muscle aches
• Diarrhea

• Vomiting

Exams and Tests

If you think you have been exposed to swine influenza, call your health care provider before your visit. This will give the staff a chance to take proper precautions to protect them and other patients during your office visit.
You will need to be tested for swine flu within the first 4 to 5 days of illness, when your risk of spreading the virus is high. Your doctor might perform the following tests:

• Auscultation (to detect abnormal breath sounds)
• Chest x-ray
• Nasopharyngeal swab (a swab of the back of the inside of your nose) to examine for the swine flu virus or to grow it in a culture
• White blood cell differential

• Complete blood count

Treatment

The CDC recommends treating only those suspected of having swine flu with antiviral drugs. If you have a fever and a respiratory illness, your physician is more likely to suspect you have swine flu when:

• You recently traveled to Mexico.
• You were in contact with someone who had a flu-like illness and was in Mexico 7 days before their illness began.
• You live in an area of the U.S. where swine flu has been confirmed.
• You were in contact with someone who had a flu-like illness and lives in an area of the U.S. where swine flu has been confirmed.

The CDC recommends treating swine flu infection with zanamivir (Relenza) alone or oseltamivir (Tamiflu) combined with either amantadine or rimantadine. These medicines can make other strains of the flu less severe -- if you start taking medication within 48 hours after your symptoms start.

To prevent infection with swine flu, people living in the same house as someone diagnosed with the virus should ask their doctor if they also need a prescription for these medicines. Careful respiratory hygiene and frequent hand-washing are also recommended steps for reducing the risk of getting swine flu.

Aspirin or products that contain aspirin should not be given to anyone 18 years old or younger.

Outlook (Prognosis)

The outlook depends on the severity of the infection and the type of swine influenza virus that caused it.
The H1N1 swine flu outbreak in Mexico has resulted in more than 150 deaths thus far. At least one death had been reported in the U.S. at the time of this writing. Officials were preparing for more.
For more information, visit the CDC at www.cdc.gov/swineflu.

Possible Complications

Severe illness may occur along with:

• Pneumonia
• Respiratory failure
• Death

Like seasonal flu, swine flu may make other chronic medical problems worse.
A vaccination used to treat swine flu in 1976 was associated with some cases of Guillain-Barre syndrome, a disorder that leads to nerve inflammation that causes muscle weakness.

When to Contact a Medical Professional

Call your health care provider if you live in an area with a known swine flu outbreak, or if you develop flu-like symptoms within 10 days of handling infected pigs or traveling to an area with a known swine flu outbreak.
Prevention
The U.S. Department of Homeland Security declared a public health emergency in April 2009. All non-essential travel to Mexico should be avoided.
People who work with pigs who might be infected should use protective clothing and special breathing masks.
Other steps you can take:

• Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue away after using it.
• Wash your hands often with soap and water, especially after you cough or sneeze. You may also use alcohol-based hand cleaners.
• Avoid touching your eyes, nose, or mouth, to avoid getting infected by germs.
• Avoid close contact with sick people.
• If you do get sick, consider staying home from work or school.

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Review Date: 4/29/2009
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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