Skip to main content
Skip to page content

Skip Navigation LinksPennsylvania Department of Health > My Health > A-Z Health Topics > I-L > Flu What You Need To Know

Influenza (Flu) What You Need to know


 Did you know? Every year an estimated 20,000 children younger than 5 years old are hospitalized for flu complications. Like pneumonia. Everyone in your family who is 6 months and older should get a flu vaccine. This year, Next year, Every year. #getafluvax


What is influenza?


Influenza (also called the “flu”) is a contagious respiratory illness caused by influenza viruses that infect the nose, throat and lungs. It can cause mild to severe illness and, at times, can lead to death. The best way to prevent the flu is by getting a flu vaccine each year.


Signs and symptoms of flu
People who have the flu often have some or all of these signs and symptoms:
·         Fever or feeling feverish/chills
·         Cough
·         Sore throat
·         Runny or stuffy nose
·         Muscle or body aches
·         Headaches
·         Fatigue (very tired)
·         Rarely, vomiting and diarrhea
How flu spreads

Influenza viruses are spread from person to person. This can happen when an infected person coughs or sneezes. Coughs and sneezes produce virus-laden droplets that can spread up to three feet through the air. Flu also can be spread when droplets from a cough or sneeze land on objects like doorknobs, light switches, etc. If others touch the objects and then touch their own mouth or nose (or someone else's mouth or nose) before washing their hands, the virus can be spread.

You can pass the flu to someone else both before and while you are sick. Adults may be able to infect others beginning one day before symptoms develop and up to five to seven days after becoming sick. Some people, especially young children and people with weakened immune systems, might be able to infect others for an even longer time.


How serious is the flu? 
Certain people are at greater risk for serious complications if they get the flu. This includes older people, young children, pregnant women and people with certain health conditions such as asthma, diabetes or heart disease (
The severity of flu seasons vary widely from one season to the next. The number of flu-associated deaths in the United States usually ranges from 3,000 to 49,000 deaths per year but can be much higher if a new strain develops to which no one is immune.
The severity of flu season depends on many things, including:
·         What flu viruses are spreading;
·         How much flu vaccine is available;
·         When vaccine is available;
·         How many people get vaccinated; and
·         How well the flu vaccine is matched to flu viruses that are causing illness.

Complications of flu

Complications of flu can include pneumonia, ear infections, sinus infections, dehydration and worsening of chronic medical conditions, such as congestive heart failure, asthma or diabetes.
Prevent seasonal flu: Get vaccinated
The single best way to prevent the flu is to get a flu vaccine each season. There are several flu vaccine options for the 2017-18 flu season. Traditional flu vaccines made to protect against three different flu viruses (called “trivalent” vaccines) are available. In addition, flu vaccines made to protect against four different flu viruses (called “quadrivalent” vaccines) also are available.
When to get vaccinated against seasonal flu
Yearly flu vaccination should begin soon after flu vaccine is available and, ideally, by October. However, getting vaccinated even later can be protective, as long as flu viruses are circulating. While seasonal influenza outbreaks can happen as early as October, influenza activity most often peaks in January or later. Since it takes about two weeks after vaccination for antibodies to develop in the body that protect against influenza virus infection, it is best that people get vaccinated to be protected before influenza begins spreading in their community.
Everyone 6 months of age and older should get a flu vaccine every season. This recommendation has been in place since Feb. 24, 2010, when CDC’s Advisory Committee on Immunization Practices (ACIP) voted for “universal” flu vaccination in the United States to expand protection against the flu to more people. Vaccination to prevent influenza is particularly important for people who are at high risk of serious complications from influenza.

Use of the nasal spray seasonal flu vaccine

For the 2017–18 season, ACIP has recommended that the live attenuated influenza vaccine (LAIV4 or FluMist) should not be used.
Additional Information:
·         Seasonal influenza factsheet
·         Recommendations for the Home 
·         Recommendations for Schools