Influenza
Viruses
Influenza, also known as the flu, is a contagious disease
that is caused by the influenza virus. It attacks the respiratory
tract in humans (nose, throat, and lungs). The flu is different
from a cold. Influenza usually comes on suddenly and may
include these symptoms:
- Fever
- Headache
- Tiredness (can be extreme)
- Dry cough
- Sore throat
- Nasal congestion
- Body aches
These symptoms are usually referred
to as "flu-like symptoms."
Anyone Can Get the Flu, But the Disease Is More Severe for
Some People
Most people who get influenza will recover in one to two
weeks, but some people will develop life-threatening complications
(such as pneumonia) as a result of the flu. Millions of people
in the United States — about 5% to 20% of U.S. residents — will
get influenza each year. An average of about 36,000 people
per year in the United States die from influenza, and 114,000
per year have to be admitted to the hospital as a result
of influenza. Anyone can get the flu (even healthy people),
and serious problems from influenza can happen at any age.
People age 65 years and older, people of any age with chronic
medical conditions, and very young children are more likely
to get complications from influenza. Pneumonia, bronchitis,
and sinus and ear infections are three examples of complications
from flu. The flu can make chronic health problems worse.
For example, people with asthma may experience asthma attacks
while they have the flu, and people with chronic congestive
heart failure may have worsening of this condition that is
triggered by the flu.
The Flu Season
In the Northern hemisphere, winter is the time for flu.
In the United States, the flu season can range from November
through March, and even past March in some years. During
the past 21 flu seasons, months with the heaviest flu activity
(peak months) occurred in December in 4 years, January in
5 years, February in 9 years, and March in 3 years.
How the Influenza Virus Is Passed Around
The main way that influenza viruses are spread is from person
to person in respiratory droplets of coughs and sneezes.
(This is called "droplet spread.") This can happen
when droplets from a cough or sneeze of an infected 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.
The Flu Is Contagious
A person can spread the flu starting one day before he or
she feels sick. Adults can continue to pass the flu virus
to others for another three to seven days after symptoms
start. Children can pass the virus for longer than seven
days. Symptoms start one to four days after the virus enters
the body. Some persons can be infected with the flu virus
but have no symptoms. During this time, those persons can
still spread the virus to others.
How To Know if You Have
the Flu
Your respiratory illness might be the flu if you have sudden
onset of body aches, fever, and respiratory symptoms, and
your illness occurs during November through April (the usual
flu season in the Northern Hemisphere). However, during this
time, other respiratory illnesses can cause similar symptoms
and flu can be caught at any time of the year. It is impossible
to tell for sure if you have the flu based on symptoms alone.
Doctors can perform tests to see if you have the flu if you
are in the first few days of your illness.
What You Should Do If You Get the Flu
- Rest
- Drink plenty of liquids
- Avoid using alcohol and tobacco
- Take medication to relieve
the symptoms of flu
Influenza is caused by a virus, so antibiotics (like penicillin)
don't work to cure it. The best way to prevent the flu is
to get an influenza vaccine (flu shot) each fall, before
flu season.
Do Not Give Aspirin To a Child or Teenager Who Has the
Flu
Never give aspirin to children or teenagers who have flu-like
symptoms – and particularly fever – without first
speaking to your doctor. Giving aspirin to children and teenagers
who have influenza can cause a rare but serious illness called
Reye syndrome. Children or teenagers with the flu should
get plenty of rest, drink lots of liquids, and take medicines
that contain no aspirin to relieve symptoms.
The Myth of
the "Stomach Flu"
Many people use the term "stomach flu" to describe
illnesses with nausea, vomiting, or diarrhea. These symptoms
can be caused by many different viruses, bacteria, or even
parasites. While vomiting, diarrhea, and being nauseous
or "sick to your
stomach" can sometimes be related to the flu – particularly
in children – these problems are rarely the main symptoms
of influenza. The flu is a respiratory disease and not
a stomach or intestinal disease. |
