Influenza is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs. It can cause mild to severe illness and on occasion can lead to hospitalization and even death. Flu seasons are unpredictable and, although seasonal flu is widespread every year, the timing, severity, and length of the epidemic depends on many factors including which viruses are spreading and whether they match the viruses in the vaccine.
Although unpredictable, flu activity usually begins in October/November and then peaks in January or February and can occur as late as May.
The signs and symptoms of the flu include:
- Sore throat
- Runny or stuffy nose
- Muscle or body aches
- Some people may also have vomiting and diarrhea, though this is more common in children than adults
Experts agree that flu viruses spread mainly by droplets made when people with the flu cough, sneeze or talk. Less often, a person may contact the flu by touching a surface or object that has the flu virus on it and then touch his or her own mouth, eyes or nose.
You may be able to pass on the flu to someone else even before you know that you are sick, as well as when you are sick. The usual period of contagion is one day before symptoms develop and up to 5 to 7 days after becoming sick. Some people, especially young children and those with weakened immune systems, might be able to infect others for an even longer time.
The single best way to prevent seasonal flu is to be immunized with flu vaccine every year. The vaccine is changed a bit every year based on projections by immunologists predicting which strains of flu will affect us.
There are two types of vaccine, flu shots or inactivated flu vaccine given by injection and recommended for everyone ages 6 months and up and live attenuated (weakened) flu vaccine given through a nasal spray, recommended for healthy people 2 to 49 years of age who are not pregnant.
It is important to note that it will take about 2 weeks for antibodies against the flu to develop and the flu vaccine will not protect patients against flu-like illness not caused by the influenza virus. Yearly flu vaccination should begin in September or as soon as the vaccine becomes available and continue throughout the flu season.
Some individuals are at higher risk for developing flu-related complications. These people include:
- Children younger than 2 years of age
- The elderly
- Pregnant women
- People with chronic medical conditions (asthma, heart disease, chronic lung disease) and people with a weakened immune system (diabetes, HIV)
- People younger than 19 who are receiving long-term aspirin therapy
- American Indians and Native Alaskans