Recognize the Symptoms of Flu

The flu is different from a cold and usually comes on suddenly. Symptoms of flu often include, fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue. Learn how to recognize symptoms of flu and how to tell the difference between a cold and the flu.

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Flu Symptoms & Severity

What are the signs and symptoms of the flu?

Flu vs Cold

Signs and Symptoms	Influenza	Cold
Symptom onset	Abrupt	Gradual
Fever	Usual; lasts 3-4 days	Rare
Aches	Usual; often severe	Slight
Chills	Fairly common	Uncommon
Fatigue, weakness	Usual	Sometimes
Sneezing	Sometimes	Common
Stuffy nose	Sometimes	Common
Sore throat	Sometimes	Common
Chest discomfort, cough	Common; can be severe	Mild to moderate; hacking cough
Headache	Common	Rare

Flu Symptoms

Influenza (also known as the flu) is a contagious respiratory illness caused by flu viruses. It can cause mild to severe illness, and at times can lead to death. The flu is different from a cold. The flu usually comes on suddenly. People who have the flu often feel some or all of these symptoms:

Fever* or feeling feverish/chills
Cough
Sore throat
Runny or stuffy nose
Muscle or body aches
Headaches
Fatigue (tiredness)
Some people may have vomiting and diarrhea, though this is more common in children than adults.

* It's important to note that not everyone with flu will have a fever.

Flu Complications

Most people who get influenza will recover in a few days to less than two weeks, but some people will develop complications (such as pneumonia) as a result of the flu, some of which can be life-threatening and result in death.

Pneumonia, bronchitis, sinus and ear infections are examples of complications from flu. The flu can make chronic health problems worse. For example, people with asthma may experience asthma attacks while they have the flu, and people with chronic congestive heart failure may experience worsening of this condition that is triggered by the flu.

People at High Risk from Flu

Anyone can get the flu (even healthy people), and serious problems related to the flu can happen at any age, but some people are at high 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 women, and young children.