Influenza usually starts suddenly and may include the following symptoms:
Having these symptoms does not always mean that you have the flu. Many different illnesses, including the common cold, can have similar symptoms.
It is very difficult to distinguish the flu from other infections on the basis of symptoms alone. A doctor’s exam may be needed to tell whether you have developed the flu or a complication of the flu. There are tests that can determine if you have the flu as long you are tested within the first 2 or 3 days of illness.
If you develop flu-like symptoms and are concerned about your illness, especially if are at high risk for complications of the flu, you should consult your healthcare provider. Those at high risk for complications include people 65 years or older, people with chronic medical conditions (such as asthma, diabetes, or heart disease), pregnant women, and young children.
In some people, the flu can cause serious complications, including bacterial pneumonia, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma or diabetes. Children and adults may develop sinus problems and ear infections.
The flu can cause mild to severe illness and at times can lead to death. Although most healthy people recover from the flu without complications, some people, such as older people, young children, and people with certain health conditions (such as asthma, diabetes, or heart disease), are at high risk for serious complications from the flu.
The flu usually spreads from person to person in respiratory droplets when people who are infected cough or sneeze. People occasionally may become infected by touching something with influenza virus on it and then touching their mouth, nose or eyes.
Healthy adults may be able to infect others 1 day before getting symptoms and up to 5 days aftergetting sick. Therefore, it is possible to give someone the flu before you know you are sick as well as while you are sick.
The single best way to protect yourself and others against influenza is to get a flu vaccination each year. Two kinds of flu vaccine are available in the United States:
Yearly flu vaccination should begin in September or as soon as vaccine is available and continue throughout the influenza season, into December, January, and beyond. This is because the timing and duration of influenza seasons vary. While influenza outbreaks can happen as early as October, most of the time influenza activity peaks in January or later.
Antiviral drugs are available to treat and prevent the flu. For more about treating the flu with antiviral drugs, see Influenza Antiviral Drugs.
* “Healthy” indicates persons who do not have an underlying medical condition that predisposes them to influenza complications.