Flu (Influenza)

The flu is a contagious respiratory illness caused by influenza viruses. Researchers identified the first virus in the 1930s. Since then, they have classified influenza viruses into types A, B, and C.

• Type A is the most common and usually causes the most serious epidemics.
• Type B outbreaks also can cause epidemics, but the disease it produces generally is milder than that caused by type A.
• Type C viruses, on the other hand, never have been connected with a large epidemic.

Flu viruses spread mainly from person to person through coughing or sneezing of people with influenza. Sometimes people may become infected by touching something with flu viruses on it and then touching their mouth or nose. Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 days after becoming sick. That means that you may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick.

Every year in the United States, on average:

• 5% to 20% of the population gets the flu;
• more than 200,000 people are hospitalized from flu complications, and;
• about 36,000 people die from flu.

Some people, such as older people, young children, and people with certain health conditions, are at high risk for serious flu complications.

Symptoms and Complications

Symptoms of flu include:

Complications of flu can include bacterial pneumonia, ear infections, sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.

Vaccines

The single best way to prevent the flu is to get a flu vaccination each year. There are two types of vaccines:

• The "flu shot" - an inactivated vaccine (containing killed virus) that is given with a needle. The flu shot is approved for use in people 6 months of age and older, including healthy people and people with chronic medical conditions.
• The nasal-spray flu vaccine - a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for "Live Attenuated Influenza Vaccine". LAIV is approved for use in healthy people 5 years to 49 years of age who are not pregnant.

About two weeks after vaccination, antibodies develop that protect against influenza virus infection. Flu vaccines will not protect against flu-like illnesses caused by non-influenza viruses.

Treatment

Many people treat their flu by simply

• Resting in bed
• Drinking plenty of fluids
• Taking over-the-counter medicine such as aspirin or acetaminophen (Tylenol, for example)

The health care provider may prescribe an antiviral medicine to treat flu:

• Tamiflu (oseltamivir) is for treating influenza A and B virus infections in adults and children 1 year and older.
• Relenza (zanamivir) is for treating influenza A and B virus infections in children 7 years and older and adults who have an uncomplicated flu infection and who have had symptoms for no more than 2 days.

To work well, you must take these medicines within 48 hours after the flu begins. They reduce the length of time fever and other symptoms last and allow you to more quickly return to your daily routine.

NOTE: Because of influenza A virus resistance to rimantadine and amantadine, CDC currently recommends that you not take these medicines to treat the flu.

Do not give aspirin to children and adolescents who have the flu.

Do not take antibiotics to treat the flu because they do not work on viruses. Antibiotics only work against some infections caused by bacteria.

References:

Centers for Disease Control and Prevention, USA.
National Institute of Allergy and Infectious Diseases, USA.