Pandemic (H1N1) Influenza
(Swine Flu; Swine Influenza; Human Swine Flu; Global Swine Flu; Pig Flu; Novel H1N1 Flu; New H1N1 Flu; H1N1 Flu; H1N1 Infection; Influenza A (H1N1); Type A (H1N1) Flu)
by Rebecca J. Stahl, MA and Brian S. Alper, MD, MSPH
As of August 2010, pandemic H1N1 flu is no longer considered a pandemic. This fact sheet provides historical information about pandemic H1N1 flu and will no longer be updated.
Pandemic H1N1 flu (originally called swine flu) is a respiratory infection. The pandemic H1N1 flu has spread to humans and has reached the level of a pandemic. A pandemic is a worldwide outbreak.
The pandemic H1N1 flu can cause mild to severe symptoms. If you think that you have this virus, call your doctor (or do as advised by local public health officials).
There are 2 main types of influenza virus—type A and type B. This strain passes from human to human, so it may spread rapidly.
The pandemic H1N1 flu spreads in the same way as the seasonal flu:
The main risk factor for getting the pandemic H1N1 flu is contact with an infected person. Having a chronic health condition (cardiovascular disease, respiratory disease, diabetes, cancer) may increase your risk of a more severe form of the infection. Also, people with physical or mental disabilities may be more at risk because they may not be able to easily communicate their symptoms or may have trouble practicing preventive measures against the pandemic H1N1 flu.
People younger than 25 years old are more likely to be affected by the virus. The pandemic H1N1 flu is more likely to affect younger people than the elderly because older people may have developed immunity against the virus.
Eating pork or pork products and drinking tap water are not risk factors for getting the pandemic H1N1 flu.
Factors that may increase your chance of complications from the pandemic H1N1 flu include:
Pandemic H1N1 flu may cause:
Call your doctor (or do what is advised by local public health officials) if both of the following apply to you:
See your doctor if you notice your symptoms worsening or you do not begin to feel better 3 days after your symptoms first appear.
If the pandemic H1N1 flu becomes severe, it can cause pneumonia. Deaths have occurred, but this has been rare. The pandemic H1N1 flu can also worsen medical conditions you may already have.
Seek urgent medical care if you have emergency warning signs.
The doctor will ask about your symptoms and medical history. Diagnosis of the flu is usually based on symptoms.
In some cases, your doctor may take samples from your nose or throat to confirm the diagnosis.
Talk with your doctor about the best treatment plan for you.
Do not use products sold on the Internet claiming to treat the pandemic H1N1 flu. Talk to your doctor before using such products.
Most people with the flu do not need antiviral medications. If you have the flu, check with your doctor to see if you need antiviral medication. You will need it if you are in a high-risk group or if you have a severe illness, such as breathing problems.
Antiviral medications do not cure the flu. They may help relieve symptoms and shorten the time you are sick. They must be taken within 48 hours of the first symptoms.
Oseltamivir (and perhaps zanamivir) may increase the risk of self-injury and confusion shortly after taking, especially in children. Children should be closely monitored for signs of unusual behavior.
Some antiviral medications sometimes used to treat some kinds of seasonal flu do not work against the pandemic H1N1 flu.
Note: Aspirin can cause serious complications in some children with certain infections. It is best to avoid aspirin or aspirin products for children with infections.
There are other measures you can take, such as:
Talk to a doctor or pharmacist if you are taking more than one drug. Some drugs can be dangerous when mixed. This includes OTC medications and herb or dietary supplements.
A pandemic H1N1 flu vaccine is available. The vaccine comes in 2 forms: a nasal spray and a shot. The nasal spray will be given in 2 doses (given one month apart) for children aged 2-9 years and in 1 dose for persons aged 10-49 years. The shot will be given in 2 doses (given one month apart) to children aged 6 months to 9 years old and in one dose for people aged 10 years and older. Make sure you talk to your healthcare provider about which vaccine is right for you.
Ways to Avoid Getting the Pandemic H1N1 Flu
There are general measures you can take to reduce your risk of getting the virus:
If you are taking care of someone who has the pandemic H1N1 flu, follow these steps:
Preventive Medications for People at High Risk
Medications to prevent the pandemic H1N1 flu may be considered for:
Ask your doctor if you should take preventive medication.
Ways to Avoid Spreading the Pandemic H1N1 Flu
If you have the pandemic H1N1 flu, take these steps to avoid spreading it to others:
Centers for Disease Control and Prevention
World Health Organization
Public Health Agency of Canada
2009 H1N1 flu. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/h1n1flu. Accessed August 14, 2017.
Influenza in adults. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T435301/Influenza-in-adults. Updated September 27, 2016. Accessed August 14, 2017.
Seasonal influenza: flu basics. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/flu/about/index.html. Updated July 28, 2017. Accessed August 14, 2017.
Traveler's health. Centers for Disease Control and Prevention. Available at: https://wwwnc.cdc.gov/travel. Accessed August 14, 2017.
Last reviewed September 2018 by David L. Horn, MD, FACP
Last Updated: 6/12/2020
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