December 10, 2025
Pneumonia is a common lung infection that can make breathing difficult and, in some cases, become life-threatening. It happens when the air sacs in the lungs fill with fluid or pus. Each year, about 900,000 Americans are diagnosed, and around 150,000 end up in the hospital. Roughly 41,000 people die from complications, according to federal health data.
The illness can range from mild to severe. Some people recover at home with rest and medication, while others may need hospital care. Knowing how pneumonia develops, who’s most at risk, and what symptoms to watch for can help you catch it early and prevent serious illness.
Pneumonia develops when the lungs become inflamed and fill with fluid. Doctors group cases based on what caused them, where they were caught, and how they affect the lungs.
Lobar pneumonia affects one or more sections of the lungs. Bronchial pneumonia, also called bronchopneumonia, shows up in small patches across both lungs.
Most pneumonia starts with an infection. Bacterial pneumonia is the most common type and is caused by bacteria that can spread from person to person, though not everyone who’s exposed will get sick. Whether someone develops pneumonia depends on things like age, immune health, and underlying conditions. The viruses that cause viral pneumonia can also spread and often affect young children and older adults. Fungal pneumonia happens after breathing in spores from the environment and doesn’t spread between people.
There are also noninfectious forms. Aspiration pneumonia happens when food, liquid, or vomit accidentally enters the lungs. Hydrocarbon pneumonia can occur after inhaling toxic substances like gasoline, kerosene, or paint thinner.
“Walking pneumonia” is a common term people use to describe a mild case of pneumonia. It’s not a specific type of pneumonia, just one that can be easy to miss because the symptoms aren’t very strong.
Pneumonia is also described by where it’s picked up. Community-acquired pneumonia develops outside of hospitals or nursing facilities. Hospital-acquired pneumonia starts during a hospital stay. Health care-associated pneumonia affects people in long-term care or rehab centers, and ventilator-associated pneumonia can develop in patients who use breathing machines. These hospital-related cases can be more dangerous because the bacteria involved are often resistant to antibiotics.
Anyone can get pneumonia, but some people are more likely to get seriously ill. That includes:
• Children under 2
• Adults over 65
• Smokers
• People who drink heavily or use drugs
The risk also goes up for people with chronic illnesses, weak immune systems, or those recovering from another respiratory illness. People who have been recently hospitalized are also more vulnerable. Fungal pneumonia is more common among people who work in dusty areas or around bird, bat, or rodent droppings, where fungal spores can circulate.
You can lower your risk of pneumonia in several ways. Vaccines are available to protect against pneumococcal pneumonia, which is caused by Streptococcus pneumoniae, the most frequent source of the illness. Quitting smoking, limiting alcohol, washing your hands often, and keeping surfaces clean can also help. Managing chronic conditions like asthma or diabetes further protects your lungs.
For most people, pneumonia starts like a bad cold. Then it gets worse.
Common early symptoms include a runny nose, sore throat, headache, fever, and a cough. As it progresses, that cough might bring up green, yellow, or even bloody mucus. Many people also feel tired, lose their appetite, or notice chest pain when they breathe deeply or cough.
More serious symptoms can include chills, sweating, nausea, vomiting, and diarrhea. When oxygen levels drop (a condition known as hypoxia), people might feel confused, anxious, short of breath, or notice their skin turning bluish.
Certain types of pneumonia have specific signs. With aspiration pneumonia, you might cough up mucus that contains food particles. Hydrocarbon pneumonia, caused by inhaling toxic chemicals, can lead to extreme drowsiness or even a coma.
To diagnose pneumonia, doctors usually start by asking about symptoms and medical history, then listen to your lungs with a stethoscope. If they suspect pneumonia, they may order a chest X-ray, blood tests, or lab work to identify the cause.
Treatment depends on what caused the illness. Bacterial pneumonia is treated with antibiotics. Viral pneumonia often improves with rest, fluids, over-the-counter medicines, and, in some cases, antiviral prescriptions. Using a humidifier or breathing steam can help loosen mucus and ease congestion. Fungal pneumonia is treated with antifungal medication.
Severe cases usually require hospitalization. Treatment in the hospital may include oxygen therapy and intravenous fluids. If it’s not treated, pneumonia can cause serious complications such as fluid buildup around the lungs (pleural effusion), respiratory failure, a collapsed lung, abscesses, or a dangerous blood infection known as sepsis.
Pneumonia can get worse quickly, so it’s important to pay attention to your symptoms. Anyone who has chest pain, a high fever, or trouble breathing should contact a doctor right away.
With early treatment and rest, most people recover fully. But because pneumonia can become dangerous if ignored, it’s important to seek medical care right away if you think you might have it. Go to an urgent care center or emergency room if your symptoms are severe or include chills, sweating, nausea, vomiting, or diarrhea.
