After Democratic presidential candidate Hillary Clinton stumbled as she was getting into a car last weekend, the world started talking about pneumonia. She has been diagnosed with pneumonia and is being treated with antibiotics. The issue brings up questions about Clinton's health and about the seriousness of pneumonia itself. Pneumonia is a common and sometimes lethal lung infection. Dr. Matthew Schreiber, who specializes in lung disease at Medstar Washington Hospital, said the disease has multiple causes. “It can happen from any number of organisms… bacterial pneumonia or viral pneumonia,” said Schreiber. Hillary Clinton’s doctor confirmed the diagnosis of pneumonia and prescribed antibiotics that are only used for bacterial pneumonia. “With bacterial pneumonia we have more options to treat. So in some ways you can make an argument that it’s to our advantage when you have bacterial pneumonia. Viral pneumonia… you’ve all heard of the flu. The flu is incredibly common, infectious process that causes pneumonia. And, truth be told, we don’t have many options to treat that,” said Schreiber. Bed rest, fluids and medication to lower a fever are recommended for any type of pneumonia. Pneumonia is the leading cause of death worldwide for children under the age of five according to the World Health Organization. In the U.S., it sends about one million adults to the hospital every year. “The severity of it really depends on how that infection has influenced that person’s lungs and how that person’s body is reacting to it,” said Schreiber. People who already have a lung disease have a greater risk for developing a serious case of pneumonia, and older adults are more at risk than younger adults. Pneumonia is contagious. When people sneeze, they send air droplets of bacteria or viruses that others can breathe in. There are vaccines that can prevent some types of bacterial pneumonia. So can hand washing, but Dr. Schreiber said anyone can get it. “There's no vitamin or pill that you can take to prevent it, and you want to have yourself in the best physical state to handle an infection if it comes up. So being active, staying healthy, eating well are all good measures to give your body a reserve to handle an infection,” said Schreiber. Common symptoms include cough, fever, feeling tired and chest pain that gets worse when coughing. Schreiber said the best way to prevent pneumonia from becoming serious is to see a doctor when the symptoms first appear.