Seasonal Influenza
Flu viruses spread widely in the U.S. every winter, causing mild to severe respiratory illness. Flu symptoms include those of the common cold (cough, sore throat, body aches), but tend to be marked by sudden high fever, headache and extreme fatigue. Some sufferers, especially children, have nausea, vomiting and diarrhea.

Complications of flu, such as bacterial pneumonia and dehydration, can be serious and even fatal. People at high risk of complications include infants, pregnant women, the elderly, and those with various chronic health problems, especially of the heart or lungs. For more on maternal and child health issues, see Flu and Pregnancy and Flu and Your Baby.

• Children aged 6 to 23 months and household contacts of children younger than 6 months
• Children with chronic heart or lung conditions, including asthma, birth defects affecting the heart or lungs, or a history of lung problems due to prematurity; or with conditions that may make it hard to breathe or swallow, such as cerebral palsy and other nerve or muscle disorders
• Anyone in close contact with someone in a high-risk group, such as household contacts and out-of-home caregivers
• Women who will be pregnant during any part of flu season

There are several exceptions, such as individuals who are allergic to eggs. A new nasal-spray vaccine is an alternative to the injected one, but is not approved for children less than five years old, for children taking aspirin, for pregnant women, for anyone aged 50 and up, or for people with various health problems. For full information and future updates on flu and flu vaccination, see the U.S. Centers for Disease Control and Prevention (CDC) Web site.

The CDC emphasizes these common-sense ways to avoid catching flu and other infections:

• Clean your hands often. Washing your hands often will help protect you from germs.
• Avoid close contact. Avoid close contact with people who are sick. When you are sick, keep your distance from others to protect them from getting sick too.
• Stay home when you are sick. If possible, stay home from work, school, and errands when you are sick. You will help prevent others from catching your illness.
• Cover your mouth and nose. Cover your mouth and nose with a tissue when coughing or sneezing. It may prevent those around you from getting sick.
• Avoid touching your eyes, nose or mouth. Germs are often spread when a person touches something that is contaminated with germs and then touches his or her eyes, nose or mouth.

Any of four prescription drugs can make a bout of flu shorter and less severe if started within the first two days of illness. They are amantadine (Symmetrel and others), rimantadine (Flumadine), oseltamivir (Tamiflu) and zanamivir (Relenza). All but zanamivir are also FDA-approved to prevent flu in people exposed to it. No single drug is best for everyone, because the four differ in terms of who (including children of different ages) can take them, how they are given, how dosages are based on age or medical conditions, which kinds of flu viruses they combat, and what their side effects are.

Safety of these drugs for use in pregnancy is unknown, so women who are pregnant or who may become pregnant should discuss options with their obstetrical care provider. Parents should consult their child's pediatrician about which drug may be appropriate.

Avian Influenza (“Bird Flu”) and Pandemic Influenza
Wild and domesticated birds can carry a wide range of flu viruses, most of which do not infect humans. In the past three years there have been more than 130 reported cases (about half of them fatal) in which people have caught the bird flu called influenza A (H5N1), almost exclusively from close contact with sick poultry. In very rare cases, individuals appear to have caught the virus directly from others who were infected by poultry, but further human-to-human contagion has not been known to occur.

Without easy spread among humans, no epidemic can occur. However, easy spread might become possible if the virus were to undergo major genetic changes. The result could be a pandemic—a worldwide epidemic of severe disease. More details appear on the World Health Organization's avian flu Web site.

There is as yet no vaccine for use in humans to prevent H5N1 flu. Annual vaccination for seasonal flu will not prevent H5N1, but will continue to be useful against ordinary human strains of virus, and will not have adverse effects on people who catch H5N1 flu. Tamiflu is the leading candidate among antiviral drugs to treat or prevent the disease, but recently Tamiflu-resistant virus has been identified. Overprescription, overuse and personal stockpiling of Tamiflu are strongly discouraged because such practices can accelerate emergence of drug-resistant strains of virus. For information about avian flu and the pregnant woman, go to Bird Flu and Pregnancy.