The flu spreads easily by coughing, sneezing and direct contact with spit, phlegm or runny nose. At first, the flu may seem like a common cold with a runny nose, sneezing and sore throat. But colds usually develop slowly, whereas the flu tends to come on suddenly.
Flu (influenza virus) reduces the body's ability to fight other infections and in more vulnerable populations can lead to complications, the most common of which is pneumonia, (infection of the lungs) which can be deadly, especially in elderly people and those living with chronic illness.
Common signs and symptoms of the flu include:
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Fever
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Aching muscles
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Chills and sweats
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Headache
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Dry, persistent cough
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Shortness of breath
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Tiredness and weakness
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Runny or stuffy nose
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Sore throat
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Eye pain
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Vomiting and diarrhea, but this is more common in children than adults
See our fact sheet contrasting common, unlikely, and possible/severe pneumonia and COVID-19 symptoms.