Influenza
Topic Overview
What is influenza (flu)?
Influenza (flu) is a viral illness that
comes on suddenly, causing fever, shaking chills, body
aches, and other symptoms. The flu is not the same as
the common cold. When you have the flu, you will often
miss more work or school than you would with other illnesses.
You may remember the flu as one of the worst illnesses
you have had.
Most people recover without problems,
but sometimes the illness leads to a bacterial infection,
such as an ear infection, sinus infection, or bronchitis.
Good home treatment may help prevent these infections.
More serious complications, most commonly pneumonia, may
develop in some people. Most deaths occur in those who
are older or whose immune systems are not working properly.
What causes the flu?
Influenza viruses A and B cause the classic
flu. Type A is usually responsible for the outbreaks that
occur annually.
These viruses may have offshoots, called
subtypes or strains, that are different from the original
virus but retain some of its characteristics. Strains
of influenza virus that cause the flu may differ from
year to year.
What are the symptoms of the flu?
The flu causes fever, cough, shaking
chills, body aches, headache, and fatigue. These symptoms
usually last for 3 to 4 days, after which you may have
a dry cough, runny nose, and sore or scratchy throat for
another week or so.
Although people often use the term "flu"
to describe any kind of mild illness that has flulike
symptoms (such as the common cold or a stomach virus),
the flu is a distinct viral illness with specific symptoms,
and it tends to occur at a particular time of year—late
fall and winter.
Do I need to see a doctor?
Most healthy people do not need to see
a doctor for the flu. The illness usually goes away in
about 7 to 10 days. Although you may feel quite sick,
home treatment is usually all that is needed.
However, you should see a health professional
for a fever if:
- An infant under age 3 months has
a fever of 100.4°F (38°C) or higher.
- A child age 3 months to 3 years has
a fever of 104°F (40°C) or higher that does
not come down after 4 to 6 hours of home treatment.
- A person age 4 or older has a fever
of 104°F (40°C) or higher that does not come
down after 2 hours of home treatment.
- Your fever does not begin to go down
after 3 to 5 days.
- You have a fever that goes away and
then returns. You could have a bacterial infection.
- You or your child also has shortness
of breath or other breathing problems.
- You or your child has a fever and
a severe headache or stiff neck, or seems confused or
hard to wake.
How is the flu treated?
Home treatment is usually all that is
needed for flu symptoms. However, antiviral medications
are available to reduce the duration and severity of symptoms.
These medications are especially useful for older adults
and others who are at risk for developing complications
from the flu. These medications need to be started within
2 days of your first symptoms.
How can I prevent the flu?
A yearly flu shot is recommended for
anyone at risk of complications from the flu and for anyone
who comes into contact regularly with people at risk.
People who should receive a flu shot include those younger
than 4 or older than 65 and those who have lung diseases,
heart failure, or medical conditions that impair their
immune system.
Flu vaccines are most effective
when the strains of virus in the vaccine match those that
are causing illness during the current flu season.
