What is H1N1 Influenza ( H1N1 flu )

H1N1 Influenza is a respiratory illness caused by the H1N1 virus. A respiratory illness affects parts of the body that are involved in breathing, including the nose, throat, and lungs.

H1N1 flu is a variety of influenza A. It was first called swine flu because it was like a virus that commonly affects pigs. H1N1 flu symptoms may be slightly more severe than symptoms that are caused by other types of seasonal flu.

The first outbreak of H1N1 flu in people occurred in 2009. After the virus spread from pigs to people, it eventually changed into the type of virus that can pass from person to person (is contagious), like other flu viruses. You cannot get the virus by eating pork.

What are the causes?

H1N1 flu is caused by the H1N1 virus. You can catch the virus by:

• Breathing in droplets from an infected person’s cough or sneeze (respiratory secretions).
• Touching something that has been exposed to the virus (has been contaminated) and then touching your mouth, nose, or eyes.

What increases the risk?

You may be at higher risk for H1N1 flu if you:

• Are age 65 or older.
• Are younger than age 5.
• Live in a nursing home or hospital.
• Are a young adult on aspirin therapy.
• Have a weak disease-fighting system (immune system).
• Are pregnant.
• Have a long-term (chronic) disease.

What are the signs or symptoms?

Signs and symptoms may start 3–5 days after infection. They may include:

• Fever.
• Chills.
• Muscle aches (myalgia).
• Tiredness.
• Loss of appetite.
• Cough.
• Runny nose.
• Sore throat.
• Headache.
• Nausea.
• Vomiting or diarrhea. (These symptoms are less common.)

How is this diagnosed?

This condition may be diagnosed based on your symptoms, your medical history, and a physical exam. In some cases, a swab of fluid from your nose or throat may be tested for the H1N1 virus.

How is this treated?

H1N1 flu usually goes away in 4–8 days without treatment. Taking care of yourself at home may be all that you need to do during this time. Your health care provider may recommend taking over-the-counter medicines, drinking plenty of fluids, and adding humidity to the air in your home.

If you are at risk for severe flu, you may be treated with antiviral medicine. If this medicine is taken soon enough, it can shorten the illness and make it less severe.

Follow these instructions at home:

Medicines

• Take over-the-counter and prescription medicines only as told by your health care provider.
• If you were prescribed antiviral medicine, take it as told by your health care provider. Do not stop taking it even if you start to feel better.
• Do not give aspirin to a child with the flu, because of the association with Reye syndrome.

Activity

• Rest at home while you recover.
• Prevent spreading H1N1 flu to others. Take the following steps until your fever has been gone for 24 hours without the use of medicine:
  • Avoid leaving home. Stay home from work or school.
  • Stay away from pregnant women, the elderly, young children, and people with chronic medical conditions.

General instructions

• Use a cool-mist humidifier to add humidity to the air in your home. This can make breathing easier.
• Cover your mouth and nose when you cough or sneeze.
• Do not prepare food for others while you are infected.
• Wash your hands with soap and water often, especially after you cough or sneeze. If soap and water are not available, use hand sanitizer.
• Make sure that all people in your household wash their hands well and often.
• Drink enough fluid to keep your urine pale yellow.
• Keep all follow-up visits as told by your health care provider. This is important.

How is this prevented?

• Getting a yearly (annual) flu shot is the best way to prevent the flu. You may get the flu shot in late summer, fall, or winter. Ask your health care provider when you should get your flu shot.
• Wash your hands with soap and water often, especially after you cough or sneeze. If soap and water are not available, use hand sanitizer.
• Avoid contact with people who are sick during cold and flu season. Wear a mask to protect yourself when you are around people who are sick or might be sick.
• Eat a healthy diet, drink plenty of fluids, get enough sleep, and exercise regularly.
• Do not touch your face if you have not cleaned your hands.

Contact a health care provider if:

• You develop new symptoms.
• You have severe symptoms that do not get better with home care.
• You have flu symptoms:
  • That last longer than one week.
  • That come back.

Get help right away if:

• You have trouble breathing.
• You have chest pain.
• You cough up blood or yellow or gray fluid.
• You feel dizzy or you faint.
• You feel confused.
• You lack energy (are lethargic).

Summary

• H1N1 flu (influenza H1N1) is a respiratory illness caused by the H1N1 virus. Symptoms may be slightly more severe than symptoms that are caused by other types of seasonal flu.
• H1N1 flu usually goes away in 4–8 days without treatment. Taking care of yourself at home may be all that you need to do during this time.
• Stay home from work or school until your fever has been gone for 24 hours without the use of medicine.
• Getting a yearly (annual) flu shot and practicing good hand hygiene may help to prevent the flu.