Overview
Flu, also called influenza, is an infection of the nose, throat and lungs, which are part of the respiratory system. The flu is caused by a virus. Influenza is commonly called the flu, but it’s different from the stomach “flu” viruses that cause diarrhea and vomiting.
Most people with the flu get better on their own.
But sometimes, influenza and its complications can be deadly. Some groups of people are at a higher than average risk of having flu complications, including:
- Young children, especially those age 12 months or younger.
- People who plan to be pregnant, are pregnant or recently gave birth during flu season.
- Adults older than age 65.
- People who live or work in facilities with many other residents. Examples are those in nursing homes and military barracks, as well as people who are in the hospital.
And in the United States, some groups have a higher risk of needing treatment in the hospital for flu. Those groups include people who are American Indian or Alaska Native, Black or Latino.
Other groups at high risk for flu complications include people with:
- Weakened immune systems.
- A body mass index (BMI) of 40 or higher.
- Nervous system disorders or conditions that change how the brain processes information.
And people with certain medical conditions have a higher risk of flu complications, such as:
- People who have chronic illnesses, such as asthma, heart disease, kidney disease, liver disease and diabetes.
- People who have had strokes.
- People who are younger than 20 years of age and receiving long-term aspirin therapy.
Although the annual influenza vaccine isn’t 100% effective, it lowers the chances of having severe complications from the flu. This is especially true for people who are at high risk for flu complications.
Symptoms
At first, the flu may seem like a cold with a runny nose, sneezing and sore throat. Colds usually start slowly. But the flu tends to come on quickly. And while a cold can be miserable, you usually feel much worse with the flu.
Common symptoms of the flu often — but not always — include a fever as well as aching muscles, chills and sweats.
Other symptoms include:
- Headache.
- Dry, persistent cough.
- Shortness of breath.
- Tiredness and weakness.
- Runny or stuffy nose.
- Sore throat.
- Eye pain.
Vomiting and diarrhea also are flu symptoms. But they are more common in children than in adults.
When to see a doctor
Most people who get the flu can treat themselves at home and often don’t need to see a healthcare professional.
If you have flu symptoms and are at risk of complications, see your healthcare professional right away. Taking antiviral medicine to treat the flu may shorten the length of your illness and help prevent more-serious problems.
If you have emergency symptoms of the flu, get medical care right away. For adults, emergency symptoms can include:
- Difficulty breathing or shortness of breath.
- Chest pain.
- Ongoing dizziness.
- Seizures.
- Worsening of existing medical conditions.
- Severe weakness or muscle pain.
Emergency symptoms in children include all the symptoms seen in adults, as well as:
- Gray or blue, lips or nail beds.
- Dehydration.
