Flu Basics

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What is influenza (also called “the flu”)? 

Influenza is commonly called the flu. It is a contagious respiratory illness caused by viruses that infect the nose, throat, and lungs. Flu can cause mild to severe illness, and at times can lead to death. There are two main types of flu viruses: A and B. Each type includes many different strains that tend to change from year to year. The best way to prevent flu is by getting a flu vaccine each year.  

Who can get the flu? 

Anyone can get the flu, but it is most serious in young children, older persons, in people with chronic illnesses (e.g., lung disease, heart disease, cancer, or diabetes) or those with weakened immune systems. 

How does the flu spread?

People with flu can spread it to others. The flu spreads mainly by droplets made when people with flu cough, sneeze, or talk.  Less often, people may become infected by touching something with influenza virus on it and then touching their mouth, nose or possibly their eyes before washing their hands. 

Most people are more likely to spread flu to others during the first 3 days of their illness. People can spread flu to others beginning 1 day before symptoms start and up to 5 to 7 days after becoming sick. This can be longer in some people, especially children and people with weakened immune systems. Some people can spread flu to others when they do not have symptoms. 

What are flu symptoms?

Symptoms of flu often start suddenly. Symptoms usually appear 1 to 4 days after exposure to the flu virus. People with the flu may have some or all of these symptoms: 

  • Fever or feeling feverish/ having chills 
  • Cough 
  • Sore throat 
  • Runny or stuffy nose 
  • Muscle or body aches 
  • Headaches 
  • Fatigue (feeling very tired) 
  • Some people may have vomiting and diarrhea (more common in children) 

Risks for Severe Illness  

Flu illness can range from mild to severe. Certain people are at higher risk of developing serious flu-related complications if they get sick. This includes people 65 years and older, people of any age with certain chronic medical conditions (such as asthma, diabetes, or heart disease), pregnant people, and children younger than 5 years.  

Complications of flu can include bacterial pneumonia, ear infections, sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes. 

Although most people are ill for less than a week, serious complications can lead to hospitalization and even death. 

What should I do if I have the flu? 

If have symptoms of the flu, you should stay home away from others and get treatment, called flu antivirals, if eligible. 

Learn more about what to do if you’re sick with the flu or other common respiratory viruses on VDH’s What To Do If You’re Sick webpage 

How can the flu be prevented? 

  • Everyone aged six months and older should get a flu vaccine each year.  
    • Flu vaccines have been shown to reduce flu related illnesses and the risk of hospitalization or even death from flu.  
    • Talk to a healthcare provider about which flu vaccines are recommended for you and your family. 
  • Everyday preventive actions can prevent the flu, including: 
    • Staying home when sick 
    • Covering coughs and sneezes 
    • Frequent handwashing 
    • Taking steps for cleaner air 

Learn more about how to prevent flu and other respiratory viruses on VDH’s Prevent the Flu webpage. 

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Last Updated: December 4, 2024