This week, presidential candidate Hillary Clinton made news -- not for what she said, but for her health.

Her political campaign announced that Clinton had pneumonia after she appeared weak at a public event in New York City. The former Secretary of State left the event suddenly. A video showed several people helping her into a waiting vehicle.

So, what is pneumonia? And how does it spread?

Simply stated, pneumonia is an infection of the lungs. It is treatable and preventable. However, pneumonia is the leading cause of death among children under five. And it was still responsible for nearly one million deaths in 2015. That information comes from the World Health Organization.

Pneumonia most often results from a bacteria called the Streptococcus pneumoniae. But viruses like influenza, and even fungi can cause pneumonia. Bacterial pneumonia is the most common kind of the disease. Pneumonia can often result from the flu.

Once the disease gets in a person's lungs, the air sacs, or alveoli, that take in oxygen, fill up with fluid. This makes breathing difficult and painful. It can limit the amount of oxygen a person takes into their body with each breath. It also causes coughing and an increase in body temperature. This makes the person feel cold.

Those most at risk are the very young, the older adults (over the age of 65) and anyone with a weak immune system.

Identification and Treatment

The signs of pneumonia look like those of the flu and the common cold. So, it is best to seek out trained medical help.

The American Lung Association says a doctor will listen to your lungs for "crackling, bubbling, and rumbling sounds" while you breathe. A follow up chest X-ray test may also be necessary.

For viral pneumonia, doctors can tell the patient to take anti-viral medication. The disease can often last 1-3 weeks in people, who are generally healthy.

For people who get bacterial pneumonia, treatment for mild cases can include antibiotics, rest and fluids. The recovery time is similar to that for viral pneumonia.

Mycoplasma pneumoniae is another bacterial form of the disease, it is known as "walking pneumonia." It is generally mild, but a full recovery may take an extended period of time, especially for the young, unhealthy and older adults.

Prevention

Preventing pneumonia requires the same steps used to prevent colds and the flu.

The American Lung Association states that pneumonia is often spread through coughing or even breathing. The group warns that people who don't show signs of pneumonia can also spread the disease.

It urges Americans to get a flu vaccination every year. In addition, "Children younger than 5, and adults 65 and older should get vaccinated against pneumococcal pneumonia."

The American Lung Association also urges people to wash your hands early and often, don't smoke and get plenty of rest and exercise.

I'm Ashley Thompson.

Kevin Enochs reported on this story for VOANews. Anna Matteo adapted this story for Learning English. George Grow was the editor.

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fungi - n. plural for the word fungus. any one of a group of living things that often look like plants, but have no flowers, and that live on dead or decaying things

coughing - v. forcing air through one's throat with short, loud noises

immune system - n. the body's natural defenses against disease

crackling - adj. a series of short, sharp noises

bubbling - adj. of or related to small balls of air or gas inside a liquid

rumbling - adj. a low, heavy sound or series of sounds