Influenza (flu) is a
viral infection. People often use the term "flu" to
describe any kind of mild illness, such as a cold or a
stomach virus, that has symptoms like the flu. But the
real flu is different. Flu symptoms are usually worse than a cold and last
longer. The flu usually does not cause vomiting or diarrhea in adults.
flu outbreaks happen in late fall and winter. Because symptoms may not start for a couple of days, you may pass
the flu to someone before you know you have it.
The flu is caused by
influenza viruses A and B. There are different strains of the flu
virus every year.
The flu causes a fever,
body aches, a headache, a dry cough, and a sore or dry throat. You will
probably feel tired and less hungry than usual. The symptoms usually are the
worst for the first 3 or 4 days. But it can take 1 to 2 weeks to get completely
It usually takes 1 to 4 days to get symptoms of the flu
after you have been around someone who has the virus.
get better without problems. But sometimes the flu can lead to a bacterial
infection, such as an
ear infection, a
sinus infection, or
bronchitis. Less often, the flu may cause a more
serious problem, such as
Certain people are at higher
risk of problems from the flu. They include young children, pregnant women,
older adults, and people with long-term illnesses or with
impaired immune systems that make it hard to fight
Your doctor will ask you
about your symptoms and examine you. This usually gives the doctor enough
information to find out if you have the flu, especially if many cases of a
similar illness have occurred in the area and the local health department
reports a flu outbreak.
In some cases, the doctor may do a blood
test or take a sample of fluid from your nose or throat to find out what type
of flu virus you have.