Learn About Pneumonia

Key Facts

• Bacteria and viruses (like the flu, the virus that causes COVID-19 and RSV) are common causes of pneumonia, a lung infection.
• While anyone can develop pneumonia, age, underlying medical conditions and behavioral factors can increase a person’s risk.
• There are vaccines available to help prevent pneumonia.

What Is Pneumonia?

Pneumonia is an infection in one or both of the lungs that may be caused by bacteria, viruses, or fungi. The infection causes the lungs' air sacs (alveoli) to become inflamed and fill up with fluid or pus. That can make it hard for the oxygen you breathe in to get into your bloodstream. The symptoms of pneumonia can range from mild to severe, and include cough, fever, chills, and trouble breathing.

Many factors affect how serious a case of pneumonia is, such as the type of germ causing the lung infection, the person’s age, their overall health and their behaviors. The people most at risk are infants and young children, adults 65 or older with risk increasing as age increases, and people who have chronic (long-term) medical conditions and weakened immune systems.

Pneumonia is a leading cause of hospitalization in both children and adults. Most cases can be treated successfully, although it can take weeks to fully recover. Tens of thousands of people in the U.S. die from pneumonia every year, most of them adults over the age of 65.

What Causes Pneumonia?

Pneumonia can be caused by a wide variety of bacteria, viruses and fungi in the air we breathe. Identifying the cause of your pneumonia can be an important step in getting the proper treatment.

Learn more about what causes pneumonia.

Who Is At Risk for Pneumonia?

Anyone can get pneumonia, and it can cause mild to serious illness in people of any age. However, there are factors that can increase your chances of getting sick and having a more severe illness. One of the most important factors is your age. People who are age 65 and over are at increased risk because their immune system is becoming less able to fight off infection as years go by. Infants and children two years of age or younger are also at increased risk because their immune systems are not yet fully developed.

Other risk factors can be grouped into three main categories: medical conditions, health behaviors, and environment.

Medical conditions

• Chronic lung diseases such as COPD, asthma, bronchiectasis, or cystic fibrosis that make the lungs more vulnerable.
• Other serious chronic illnesses, such as heart disease, liver disease, diabetes and sickle cell disease.
• A weakened immune system due to HIV/AIDs, an organ transplant, chemotherapy or long-term steroid use.
• Difficulty swallowing, due to stroke, dementia, Parkinson's disease, or other neurological conditions, which can result in aspiration of food, vomit or saliva into the lungs that then becomes infected.
• Recent illness from a respiratory virus—a cold, RSV, influenza, etc.
• Hospitalization, especially when in intensive care and using a ventilator to breathe.

Health behaviors

• Cigarette smoking, which damages the lungs.
• Person with an alcohol or substance use disorder.

Environment

• Exposure to certain chemicals, pollutants or toxic fumes, including secondhand smoke.
• Being around people who are sick. 
• Living in a long-term care facility.
• There are more germs causing respiratory illness circulating in the fall and winter, this causes more spread of respiratory illnesses within communities. People can get pneumonia at any time of the year though.