Influenza, commonly called "the flu" is caused by the influenza virus, which infects the respiratory tract (nose, throat, lungs). Unlike many viral respiratory infections, such as the common cold, the flu causes severe illness and life-threatening complications in many people.
Symptoms of flu include fever, headache, extreme tiredness, dry cough, sore throat, runny or stuffy nose, and muscle aches. Children can have additional gastrointestinal symptoms such as nausea, vomiting, and diarrhea, but these symptoms are uncommon in adults.
On average, approximately 5% to 20% of U.S. residents get the flu, and more than 200,000 persons are hospitalized for flu-related complications each year. About 36,000 Americans die on average per year from complications of flu.1
How does the flu spread? The main way that influenza viruses are spread is from person to person in respiratory droplets of coughs and sneezes. This can happen when droplets from the cough or sneeze of an affected person are propelled (generally up to 3 feet) through the air and deposited on the mouth or nose of people nearby. Though much less frequent, the viruses also can be spread when a person touches respiratory droplets on another person or an object and then touches their own mouth or nose (or someone else's mouth or nose) before washing their hands.1
Yes, anyone can get the flu and pass it along. 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 will be able to pass on the flu to someone else before you know you are sick, as well as while you are sick.2
FACT: Some of the complications caused by flu include bacterial pneumonia, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes. Children may experience sinus problems and ear infections as complications from the flu. Those aged 65 years and older and persons of any age with chronic medical conditions are at highest risk for serious complications of flu.1