INFLUENZA Q & A
What is influenza (flu)?
Influenza, commonly called “the flu,” is caused by the influenza virus, which infects the respiratory tract
(nose, throat, lungs). Unlike many other viral respiratory infections, such as the common cold, the flu
causes severe illness and life-threatening complications in many people.
What are the symptoms of the flu?
Symptoms of flu include:
 Fever
 Extreme tiredness
 Sore throat
 Muscle aches
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Headache
Dry cough
Runny or stuffy nose
Children can have additional gastrointestinal symptoms, such as nausea, vomiting, and diarrhea, but
these symptoms are uncommon in adults. Although the term “stomach flu” is sometimes used to
describe vomiting, nausea, or diarrhea, these illnesses are caused by other viruses, bacteria, or possibly
parasites, and are rarely related to influenza.
What is the difference between a cold and the flu?
The flu and the common cold are both respiratory illnesses but they are caused by different viruses.
Because these two types of illnesses have similar symptoms, it can be difficult to tell the difference
between them based on symptoms alone.
In general, the flu is worse than the common cold, and symptoms such as fever, body aches, extreme
tiredness, and dry cough are more common and intense.
Colds are usually milder than the flu. People with colds are more likely to have a runny or stuffy nose.
Colds generally do not result in serious health problems, such as pneumonia, bacterial infections, or
hospitalizations.
Special tests that usually must be done within the first few days of illness can be carried out, when
needed, to tell if a person has the flu.
When is the flu season in the United States?
In the United States, the season can begin as early as October and end as late as May. The peak of flu
season usually occurs anywhere from late December through March. The number of infections,
hospitalizations, and deaths in a flu season varies from year to year.
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 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.
If I got the flu last year, will I have immunity against the flu this year?
In general, a person who is infected with an influenza virus one year will have some immunity to
closely-related viruses that may persist for one or more years.
The degree of protection depends on the health of the person involved. Young and healthy people with
normal immune systems will likely have good immunity against the same or closely related strains of
virus from one year to the next. However, people with weakened immune systems are less likely to
have immunity that carries over in other years.
It's important to remember that influenza viruses are constantly changing, so antibody made against one
strain will become less effective against new strains as influenza strains evolve over time. In addition,
there are different types of influenza viruses circulating and different variants within virus types, and the
same type of flu virus does not necessarily circulate each year. Immunity against one doesn’t provide
immunity against all.
Does the flu have complications?
Yes. 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 get 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.
How soon will I get sick if I am exposed to the flu?
The time from when a person is exposed to flu virus to when symptoms begin is about one to four days,
with an average of about two days.
How long is a person with flu virus contagious?
The period when an infected person is contagious depends on the age and health of the person. Studies
show that most healthy adults may be able to infect others from 1 day prior to becoming sick and for 5
days after they first develop symptoms. Some young children and people with weakened immune
systems may be contagious for longer than a week.
How many people get sick or die from the flu every year?
Each flu season is unique, but it is estimated that, 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 the complications of flu.
Thanks to CDC and (insert PTA or School)