Hillary Clinton's health was in the spotlight this weekend after the Democratic nominee appeared to stumble as she left a 9/11 memorial event early.

Clinton's staff later said that she was "overheated" and "dehydrated"and disclosed that she had been diagnosed with pneumonia on Friday. The campaign released a statement from her doctor that said Clinton was "recovering nicely."

The episode prompted much speculation online and on the airwaves about the 68-year-old's health. But how serious is the condition?

Clinton was diagnosed with community-acquired pneumonia, which is a respiratory infection contracted from the outside environment. According to the National Institutes of Health, the condition is caused when bacteria or a virus enter the lungs, causing a buildup of fluid in the air sacs. Her doctor prescribed antibiotics, which could mean that the pneumonia is bacterial rather than viral. That makes it a more treatable condition. (Viral pneumonia is often a complication of the flu.)

The most common symptoms are cough, fever, shaking chills, shortness of breath, and general malaise. Treatment involves taking in plenty of fluids, bed rest, and the prescribed antibiotics.

Millions of people per year get pneumonia, and a typical timeline for recovery is around two weeks, although older adults can take longer to recover. Clinton could be dealing with atypical pneumonia, or walking pneumonia, which would allow her to continue campaigning.

Though her health has been the subject of many rumors, Clinton is essentially in good condition. She suffered a concussion in 2012 after fainting from a stomach virus, but otherwise hasn't had any major health incidents. (You can read her doctor's statement here.)

Correction: An earlier version of this story incorrectly stated that Clinton was diagnosed with pneumonia on Sunday. Her campaign says she was diagnosed on Friday. Refinery29 regrets the error.

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