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Advice for Patients
November 1, 2010

H1N1 and Seasonal Flu: The “New” Flu and the “Old” Flu

Arch Pediatr Adolesc Med. 2010;164(11):1076. doi:10.1001/archpediatrics.2010.209

The flu (influenza) is a contagious respiratory illness caused by flu viruses. It can cause mild to severe illness, and at times it can lead to death.


Seasonal flu is typically caused by either influenza A or B viruses; there are many different strains or types of these flu viruses. Each year, the seasonal flu causes illness between late fall and early spring. In a typical year, about 5% to 20% of people get the seasonal flu.

H1N1 flu is a new influenza virus that was a major cause of the flu in 2009. Two articles in this month's Archives describe children who had the 2009 H1N1 virus. Some concerns described in these articles are that children who are most at risk of hospitalization or death from the flu include:

  • Children with underlying medical problems, such as heart problems, neurologic disorders (like cerebral palsy), or metabolic disorders (like diabetes)

  • Children who were born prematurely (less than 33 weeks' gestation)

  • Children younger than 1 year


Flu symptoms may include fever, cough, sore throat, runny or stuffy nose, headaches, body aches, chills, and fatigue. With H1N1 flu infection, vomiting and diarrhea may also occur.

If your child is sick with the flu, there are antiviral medicines that can make the illness milder and shorter. These medications may also prevent complications of influenza such as hospitalization. Children younger than 5 years and children with chronic medical conditions such as asthma may benefit from antiviral medications if they get the flu. However, most people do not need these antiviral medicines to recover fully from the flu. Other treatments for the flu include rest and drinking plenty of liquids to stay hydrated.


The best way to prevent the flu is to get vaccinated. Everyone aged 6 months or older should get vaccinated against the flu. Vaccination of pregnant women is safe and can help prevent flu in their young infants.

Yearly seasonal flu vaccination usually begins in September or as soon as the vaccine is available. Children younger than 9 years will need 2 doses of the vaccine the first year they receive it.

Each year the flu vaccine is created based on the best information about what types of flu will be most likely to cause seasonal flu. The 2010-2011 seasonal flu vaccine will protect against the 2009 H1N1 virus that caused most of the illness in the 2009 season.


If your child is sick with a fever, talk to your doctor about whether he or she should get the flu shot at a later date. However, your child can get a flu shot if he or she has a respiratory illness without a fever.

Talk to your doctor about whether your child should get a flu shot if your child has ever had a severe allergic reaction to eggs, a severe allergic reaction to a previous flu shot, or has ever had Guillain-Barre syndrome.


To find this and other Advice for Patients articles, go to the Advice for Patients link on the Archives of Pediatrics & Adolescent Medicine Web site at http://www.archpediatrics.com.

Source: U.S. Department of Health and Human Services Flu Home: www.flu.gov.

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The Advice for Patients feature is a public service of Archives of Pediatrics & Adolescent Medicine. The information and recommendations appearing on this page are appropriate in most instances, but they are not a substitute for medical diagnosis. For specific information concerning your child's medical condition, Archives of Pediatrics & Adolescent Medicine suggests that you consult your child's physician. This page may be photocopied noncommercially by physicians and other health care professionals to share with patients. To purchase bulk reprints, call 312/464-0776.