What Is Influenza?

]]>Seasonal influenza]]> (also called the flu) is an upper respiratory infection. It is caused by the influenza virus. Flu strains differ from one year to the next. There are two main kinds infecting humans:

  • Type A
  • Type B

You can get the flu when you breathe in droplets from someone infected with the virus. It can also be spread by touching a contaminated surface and then putting your hand to your mouth or nose.

Each winter, the flu spreads around the world. Anyone can get it, but some are at greater risk than others:

  • People who live or work in crowded conditions (eg, nursing home, school, military, day care)
  • Newborn babies
  • Elderly
  • Women in the third trimester of pregnancy
  • People with ]]>diabetes]]>
  • People with weakened immune systems (eg, ]]>patients with cancer]]> or ]]>AIDS]]>)
  • People taking immunosuppressive drugs
  • People with chronic conditions (eg, diabetes or disorders of the lungs, heart, kidneys, or blood)

On average, 5%-20% of the US population gets the flu each year. More than 200,000 people are hospitalized for flu-related complications. About 36,000 die from the disease.

Symptoms include:

  • Fever and chills
  • Severe muscle aches
  • Cough
  • Severe fatigue
  • Headache
  • Decreased appetite, other gastrointestinal symptoms (eg, nausea, vomiting)
  • Runny nose, nasal congestion
  • Sneezing
  • Watery eyes, ]]>conjunctivitis]]>
  • ]]>Sore throat]]>
  • Swollen lymph nodes in the neck

Treatment may include:

  • Bed rest
  • Fluids
  • Over-the-counter pain relievers
  • Decongestants
  • Cough suppressants
  • Antiviral medicines

What Is the Influenza Vaccine?

There are two types of influenza vaccines:

  • Flu shot—trivalent influenza vaccine (TIV)
  • Nasal spray (FluMist)—live, attenuated influenza vaccine (LAIV)

The flu shot is approved for use in people older than six months. The shot is made from an inactivated, killed virus. It is given by injection, usually into the arm.

The nasal spray flu vaccine is approved for healthy people aged 2-49 years who are not pregnant. It is made from live, weakened flu viruses. It is taken by nasal spray.

Both vaccines contain three influenza viral strains—type A virus (H3N2), type A virus (H1N1), and a type B virus. The vaccine changes from year to year based on which viruses are likely to circulate in a given flu season.

(NOTE: The flu shot is not effective against ]]>pandemic H1N1 (2009) flu]]>. You must get the ]]>vaccine for pandemic H1N1 (2009) flu.]]>)

Who Should Get Vaccinated and When?

Anyone who wants to reduce their risk of the flu should consider the vaccine. Those who should get a yearly flu vaccine include:

  • Children six months-18 years old
  • Parents, babysitters, and caretakers of children less than six months old (as these children are too young to be vaccinated)
  • Adults older than 50 years of age (shown to reduce hospitalizations and deaths in the elderly)
  • Those living or working in nursing homes and long-term care facilities
  • Those with chronic medical conditions
  • Those with chronic diseases, such as diabetes or ]]>asthma,]]> or conditions involving the kidneys, liver, lungs, heart, blood, or immune system
  • Women who are pregnant
  • Healthcare workers
  • Those living with someone who is at high risk for complications from the flu

It takes about two weeks for the vaccination to protect you against the flu. Even if you have been vaccinated, you can still get the flu. If you have symptoms, tell your doctor.

Flu season can begin as early as October and as late as April or May. The best time to get vaccinated is as soon as the vaccine becomes available. Doing so will protect you before the flu comes to your community.

It is recommended that two doses are given (separated by four weeks or more) to children who meet certain criteria:

  • Less than nine years old and receiving influenza vaccine for the first time
  • Vaccinated last season for the first time, but with only one dose

What Are the Risks Associated With the Influenza Vaccine?

Almost all people who receive the influenza vaccine have no problems. There are certain risks associated with the vaccine. As with any vaccine, there is a small risk of serious problems, including severe allergic reaction.

Adverse effects associated with the flu shot include:

  • Soreness, redness, and swelling around the injection site
  • Low-grade fever
  • Muscle aches

Adverse effects associated with the nasal spray vaccine include:

  • Runny nose
  • Headache
  • Vomiting
  • Muscle aches
  • Fever
  • Sore throat
  • ]]>Cough]]>

Who Should Not Get Vaccinated?

Certain people should consult their doctor before receiving the influenza vaccine. These include:

  • People who have a severe allergy to chicken eggs
  • People who have had a severe reaction to a prior influenza vaccine
  • Children younger than six months
  • People who are sick with a fever

What Other Ways Can Influenza Be Prevented Besides Vaccination?

Good preventive measures include:

  • Avoid close contact with people who have respiratory infections.
  • Wash your hands often for 15-20 seconds with soap and water, especially when you come in contact with someone who is sick. Rubbing alcohol-based cleaners on your hands is also useful.
  • Do not share drinks or personal items.
  • Do not bite your nails or put your hands near your eyes, mouth, or nose.

What Happens in the Event of an Outbreak?

In the event of an outbreak, vaccinating as many susceptible people as possible, especially those in priority groups, is the primary focus. In addition, the use of antiviral medications (eg, ]]>oseltamivir]]>, ]]>zanamivir]]>) can reduce the duration of the illness when given within two days of onset. Certain antiviral medicines can also be given before exposure to Type A influenza virus to help prevent illness. Finally, people who are infected should be isolated as much as possible.