9 signs your flu might be deadly

The flu is a contagious respiratory illness that’s caused by influenza viruses, according to the Centers for Disease Control and Prevention (CDC). There are three types of influenza virus, influenza A, influenza B, and influenza C (though infections by C are mild). Influenza A can also break down into different subtypes; B doesn’t have subtypes, but it does have various lineages and strains. All of that adds up to several types of bugs that can make you sick each flu season.

What are the symptoms of the flu?

It can be difficult to determine whether you’ve come down with the flu or a cold—though one telltale is the severity of your symptoms. Cold symptoms such as a runny or stuffy nose, and a sore throat, will be much milder than flu symptoms, which include the symptoms of a cold plus a fever, chills, headaches, and extreme fatigue. If you think you might have the flu, it’s important to see your doctor who can run tests for the virus. Check out these situations that make you think you have the flu, but you really don’t.

What about the stomach flu?

Also known as gastroenteritis flu, this can also be caused by a virus—most commonly rotavirus and norovirus, says Niket Sonpal, MD, an NYC-based internist and gastroenterologist. “With gastroenteritis, the main symptoms someone will have include watery diarrhea and vomiting,” Dr. Sonpal says. “You might also have stomach pain, cramping, fever, nausea, and a headache.” Find out 8 ways to prevent getting the stomach flu.

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