Pneumonia has come under focus after U.S. Democratic presidential nominee Hillary Clinton's campaign revealed Sunday that she had been diagnosed with the infectious disease Friday. Although pneumonia can be cured, it can also be fatal in severe cases.

Pneumonia affects the lungs and results in mild to severe illness in people of all ages. Cough, fever and troubled breathing are common symptoms of the disease.

According to the U.S. Centers for Disease Control and Prevention (CDC), pneumonia claims lives of nearly 1 million children younger than 5 years of age every year globally. And in the U.S., about 1 million people get pneumonia treatment and about 50,000 people die from the disease annually.

Pneumonia spreads through the lungs and the infected area becomes inflamed, which is a part of the body’s normal response to the disease. But, those with a weak immune system cannot contain the infection.

Who Is At Risk Of Pneumonia?

People aged 65 or more and children aged younger than five are at the risk of the disease. Those suffering from health issues such as asthma, diabetes or heart disease are also at an increased risk of pneumonia. Cigarette smokers are also likely to get the disease.

How Does Pneumonia Affect Body?

Tiny air sacs at the ends of the breathing tubes become infected and start filling up with fluid and pus. This affects the normal process of gas exchange in the lungs that halts oxygen from reaching the blood stream. It also leads to rise in blood levels of the waste gas carbon dioxide, which cannot be removed easily. This causes breathing trouble.

Oxygen levels can fall down and affect the heart and brain. This can lead to coma and heart failure, and eventually cause death.