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This fact sheet provides general information. Check with your local or state public health department for specific information for your community.

Definition

H1N1 flu is a respiratory infection. It typically only affects pigs, but it can affect humans. The 2009 strain of the H1N1 flu virus can pass from human to human, so it may spread rapidly. Health experts are concerned that this could cause an influenza pandemic. A pandemic is a worldwide outbreak.

The H1N1 flu can cause mild to severe symptoms. If you think that you have this virus, call your doctor (or as advised by local public health officials).

Virus Attacking Cell

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Causes

Type A influenza viruses cause the H1N1 flu. The 2009 outbreak is due to a new subtype of the Type A strain, called H1N1.

H1N1 flu can be spread to humans from contact with infected pigs. These viruses can also spread between humans in the same way that the seasonal flu is spread:

  • By breathing in droplets after an infected person coughs or sneezes
  • By touching a contaminated surface and then touching your eyes, nose, or mouth

Risk Factors

These factors increase your chance of getting the H1N1 flu. Tell your doctor if you have any of these risk factors:

  • Having contact with infected pigs (eg, working in the swine industry, visiting a livestock exhibit)
  • Having contact with an infected person
  • Living in or traveling to Mexico (or other communities with confirmed cases)

Eating pork or pork products is not a risk factor for getting the H1N1 flu. If you properly cook pork to 160°F (70°C), this will kill the virus.

Symptoms

The following symptoms may be due to H1N1 flu. They may also be due to other conditions.

  • Fever and chills
  • Sore throat
  • Cough
  • Severe muscle aches
  • Severe fatigue
  • Headache
  • Runny nose, nasal congestion
  • Sneezing
  • Watery eyes
  • Gastrointestinal symptoms (eg, nausea, diarrhea, vomiting)

Call your doctor (or as advised by local public health officials) if both of the following apply to you:

  • You have a fever of 100°F (37.8°C) or higher and any of the following:
    • Stuffy nose (makes it hard for you to breathe through your nose)
    • Runny nose (you are wiping your nose often)
    • Cough
    • Sore throat
  • You have been exposed to the H1N1 flu by:
    • being within six feet of someone known to have the H1N1 flu, or
    • living or having traveled to a place where there have been confirmed cases of the H1N1 flu.

If the H1N1 flu becomes severe, it can cause pneumonia. Deaths have occurred, but this has been rare. The H1N1 flu can also worsen medical conditions you may already have.

Seek urgent medical care if you have emergency warning signs.

  • Emergency warning signs in adults include:
    • Trouble breathing or shortness of breath
    • Pain or pressure in chest or belly
    • Sudden dizziness
    • Confusion
    • Severe vomiting or vomiting that does not stop
    • Flu-like symptoms get better then come back with fever and worse cough
  • Emergency warning signs in children include:
    • Fast breathing or trouble breathing
    • Blue or gray skin color
    • Not drinking enough fluids
    • Not waking up or not interacting
    • Being so irritable to not want to be held
    • Flu-like symptoms get better then come back with fever and worse cough
    • Fever with a rash

Diagnosis

Your doctor will ask about your symptoms, medical history, and travel history. If you are at high risk for the H1N1 flu, your doctor may give you special instructions before you visit the hospital or doctor’s office (such as not going into the waiting room).

During your visit, your doctor will examine you and may take samples of secretions from your nose or throat. Your doctor will test these secretions for the virus.

Treatment

Talk with your doctor about the best treatment plan for you.

Do not use products sold on the Internet claiming to treat the H1N1 flu. Talk to your doctor before using such products.

Approved treatment options include the following:

Antiviral Medicines

Antiviral medicines used to treat the H1N1 flu include:

Oseltamivir (and perhaps zanamivir) may increase the risk of self-injury and confusion shortly after taking, especially in children. Children should be closely followed for signs of unusual behavior.

These medications do not cure the flu. They may help relieve symptoms and shorten the time you are sick. They should be taken within 48 hours of the first symptoms.

Other antiviral medications sometimes used to treat type A influenza (amantadine or rimantadine) do not work against the H1N1 flu.

Other Measures

There are other measures you can take, such as:

  • Getting plenty of rest to help your body fight the flu
  • Drinking a lot of liquids, including water, juice, and non-caffeinated tea
  • Taking over-the-counter (OTC) pain relievers, such as acetaminophen, ibuprofen, or (in adults) aspirin*
  • Taking other OTC products (eg, decongestants, saline nasal sprays, cough medicines)
    • Talk to your doctor about what is safe for you or your child to take. For example, cough and cold products can cause serious side effects in young children.

* Aspirin is not recommended for children or teens with a current or recent viral infection. Check with your doctor before giving a child or teen aspirin.

Prevention

Travel Precautions

For the latest travel warnings, visit the CDC's Traveler's Health page.

Vaccine

There is no vaccine to prevent the H1N1 flu.

Ways to Avoid Getting the H1N1 Flu

There are general measures you can take to reduce your risk of getting the virus:

  • Avoid close contact with people who have respiratory infections. The H1N1 flu can spread starting one day before and ending seven days after symptoms appear.
  • If you are unable to avoid crowded areas where at least one case of H1N1 flu has been confirmed, consider using a disposable face mask.
  • Wash your hands often, especially when you come in contact with someone who is sick. Rubbing alcohol-based cleaners on your hands is also helpful.
  • Do not share drinks or personal items.
  • Do not bite your nails or put your hands near your eyes, mouth, or nose.
  • If you have contact with pigs:
    • Wash your hands thoroughly and often.
    • Avoid close contact with infected pigs.

Do not use products sold on the Internet claiming to prevent the H1N1 flu. Talk to your doctor before using such products.

If you are taking care of someone who has the H1N1 flu, follow these steps:

  • To prevent areas from being contaminated, try to keep the person who is sick in one room of the house.
  • Wash your hands after having contact with the person.
  • If you cannot avoid close contact with the sick person, cover your mouth and nose with a face mask (or preferably a N95 respirator if available).
  • Limit contact with other members of the household or community while taking care of the person.
  • If you develop symptoms of a flu-like illness, call your doctor (or as advised by local public health official) immediately.
  • Remember that the person who is sick should have little contact with others and stay home from school or work.

For more information, visit the CDC's page on caring for someone with the H1N1 flu.

Preventative Medicine for People at High Risk

Medicines to prevent the H1N1 flu, such as Zanamivir (Relenza) or Oseltamivir (Tamiflu), are recommended for:

  • People who have close contact with an infected person (confirmed or suspected) and have conditions that put them at high risk for complications—You are considered at high risk if you:
    • Have a chronic health condition
    • Are aged 65 or older
    • Are aged 5 or younger
    • Are pregnant
  • People who travel to or live in Mexico and have conditions that put them at high risk for complications
  • Healthcare or public health workers who have contact with an infected person (confirmed or suspected)

Ask your doctor if you should take preventative medicine.

Ways to Avoid Spreading the H1N1 Flu

If you have the H1N1 flu, take these steps to avoid spreading it to others:

  • Avoid close contact with people. Stay home from school or work for seven days after symptoms first appear and at least 24 hours after symptoms resolve.
  • If you cannot avoid close contact, cover your mouth and nose with a face mask.
  • Wash your hands often. Rubbing alcohol-based cleaners on your hands is also helpful.
  • Cover your mouth and nose with a tissue when you cough or sneeze. Throw away the tissue after you use it. Coughing or sneezing into your elbow or upper sleeve will also keep you from spreading the flu with your hands. Do not spit.
  • Do not share drinks or personal items.
  • Do not bite your nails or put your hands near your eyes, mouth, or nose.