Influenza, or the the flu, is a contagious respiratory illness caused by an airborne virus. Influenza viruses are divided into three types: A, B and C. Type A and B viruses are the most serious and are responsible for the flu epidemics experienced nearly every winter. Type C viruses typically cause a very minor respiratory illness and may result in no symptoms at all. The annual flu vaccine targets types A and B. While type A and B viruses differ in origin, the symptoms are the same.
Signs and Symptoms
Unlike a cold, the flu usually comes on suddenly. Symptoms can be moderate to severe and typically include fever, chills, nonproductive cough, sore throat, runny or stuffy nose, muscle and body aches, headache and fatigue. Some who get the flu may also experience vomiting and diarrhea, although this is more common in children than adults. According to the Centers for Disease Control and Prevention, fever is common but does not always accompany the flu. Any fever and body aches usually last 3 to 5 days, but the cough and fatigue may last up to 2 weeks or longer. Complications can be serious and include pneumonia, bronchitis and sinus and ear infections. Young children, the elderly, pregnant women and those with compromised immune systems are at greater risk for complications.
How Flu Spreads
The flu is passed from person to person through the air. When an infected person coughs or sneezes, airborne droplets can land in the mouth or nose -- or even be inhaled into the lungs -- of others nearby. A person might also become infected by touching a surface that has the virus on it, such as a door knob, and then touching his mouth or nose. Adults are thought to be contagious 1 day before showing symptoms and 5 to 7 days after becoming sick. Children may be contagious for longer than 7 days. Symptoms usually appear within 1 to 4 days of the virus entering the body. Some people may have the flu virus and remain asymptomatic but still pass the virus to others.
Contact your doctor if you have flu symptoms. Treatment is aimed at reducing the severity of symptoms and may include medications to relieve aches and fever, bed rest and plenty of fluids. Your doctor may also prescribe antiviral medications. When started within the first 2 days, they can reduce the duration of symptoms.
The CDC recommends that everyone 6 months old and older get the annual flu vaccine. The vaccine is especially important for high-risk groups, including young children, pregnant women and the elderly. While the vaccine doesn’t protect against all flu viruses, it does protect against those that research indicates will be most prevalent, including type A viruses. In addition to getting the vaccine, avoid close contact with sick people. If you are sick with the flu, stay home and minimize contact with others until you are fever free for at least 24 hours. Cover your mouth and nose with a tissue when you cough or sneeze, and dispose of tissues properly. Wash your hands often with soap and water. Avoid touching your eyes, nose and mouth.
- Centers for Disease Control and Prevention: Summary Recommendations -- Prevention and Control of Influenza With Vaccines -- Recommendations of the Advisory Committee on Immunization Practices — (ACIP) — United States, 2013-14
- Johns Hopkins Medicine: Influenza
- Centers for Disease Control and Prevention: Clinical Signs and Symptoms of Influenza