Before we begin: The flu can cause serious illness in people over 65, babies, and people.
This tutorial walks you through everything you need to know about flu. We explain it in plain language, step by step, so whether you are a student, a patient, or simply curious, you will come away with a solid understanding.
We cover what it is, why it matters, how it is diagnosed, and what you can do about it. Key facts are called out along the way.
What is the flu? The flu, also called influenza, is a respiratory infection caused by viruses. Each year, millions of Americans get sick with the flu. Sometimes it causes mild illness. But it can also be serious or even deadly, especially for people over 65, newborn babies, and people with certain chronic illnesses.
What causes the flu? The flu is caused by flu viruses that spread from person to person. When someone with the flu coughs, sneezes, or talks, they spray tiny droplets. These droplets can land in the mouths or noses of people who are nearby. Less often, a person may get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose, or possibly their eyes.
What are the symptoms of the flu? Symptoms of the flu come on suddenly and may include:
Fever or feeling feverish/chills
Cough
Sore throat
Runny or stuffy nose
Muscle or body aches
Headaches
Fatigue (tiredness)
Some people may also have vomiting and diarrhea. This is more common in children.
Sometimes people have trouble figuring out whether they have a cold or the flu. There are differences between them:
Signs and Symptoms
Cold
Flu
Start of symptoms
Slowly
Suddenly
Fever
Rarely
Usually
Aches
Sometimes (slight)
Usually
Fatigue, weakness
Sometimes
Usually
Headache
Rarely
Common
Stuffy nose, sneezing, or sore throat
Common
Sometimes
Sometimes people say that they have a “flu” when they really have something else. For example, “stomach flu” isn’t the flu; it’s gastroenteritis.
What other problems can the flu cause? Some people who get the flu will develop complications. Some of these complications can be serious or even life-threatening. They include:
Bronchitis
Ear infection
Sinus infection
Pneumonia
Inflammation of the heart (myocarditis), brain (encephalitis), or muscle tissues (myositis, rhabdomyolysis)
The flu also can make chronic health problems worse. For example, people with asthma may have asthma attacks while they have flu.
Certain people are more likely to have complications from the flu, including:
Adults 65 and older
Pregnant women
Children younger than 5
People with certain chronic health conditions, such as asthma, diabetes, and heart disease
How is the flu diagnosed? To diagnose the flu, health care providers will first do a medical history and ask about your symptoms. There are several tests for the flu. For the tests, your provider will swipe the inside of your nose or the back of your throat with a swab. Then the swab will be tested for the flu virus.
Some tests are quick and give results in 15-20 minutes. But these tests are not as accurate as other flu tests. These other tests can give you the results in one hour or several hours.
What are the treatments for the flu? Most people with the flu recover on their own without medical care. People with mild cases of the flu should stay home and avoid contact with others, except to get medical care.
But if you have symptoms of flu and are in a high risk group or are very sick or worried about your illness, contact your health care provider. You might need antiviral medicines to treat your flu. Antiviral medicines can make the illness milder and shorten the time you are sick. They also can prevent serious flu complications. They usually work best when you start taking them within 2 days of getting sick.
Can the flu be prevented? The best way to prevent the flu is to get a flu vaccine every year. But it’s also important to have good health habits like covering your cough and washing your hands often. This can help stop the spread of germs and prevent the flu.
Centers for Disease Control and Prevention
Also known as: Grippe, Influenza, Seasonal flu.
Related topics: Grippe, Influenza.
Categories: Infections, Lungs and Breathing.
Source: National Institutes of Health — National Institute of Allergy and Infectious Diseases.
Key Takeaways
Understanding flu is an important part of taking charge of your health. Here is what to remember:
- Know the signs — Recognizing early symptoms can lead to earlier diagnosis and better outcomes.
- Talk to your provider — If you have concerns or a family history of this condition, bring it up at your next checkup.
- Stay informed — Medical knowledge evolves. Keep learning and asking questions.
- You are not alone — Many people deal with this condition. Support groups and educational resources can help.