Pneumonia is an infection that inflames the air sacs in one or both lungs. The air sacs may fill with fluid or pus (purulent material), causing cough with phlegm or pus, fever, chills, and difficulty breathing. A variety of organisms, including bacteria, viruses and fungi, can cause pneumonia.
Pneumonia can range in seriousness from mild to life-threatening. It is most serious for infants and young children, people older than age 65, and people with health problems or weakened immune systems.
The signs and symptoms of pneumonia vary from mild to severe, depending on factors such as the type of germ causing the infection, and your age and overall health. Mild signs and symptoms often are similar to those of a cold or flu, but they last longer.
Signs and symptoms of pneumonia may include:
- Chest pain when you breathe or cough
- Confusion or changes in mental awareness (in adults age 65 and older)
- Cough, which may produce phlegm
- Fever, sweating and shaking chills
- Lower than normal body temperature (in adults older than age 65 and people with weak immune systems)
- Nausea, vomiting or diarrhea
- Shortness of breath
Newborns and infants may not show any sign of the infection. Or they may vomit, have a fever and cough, appear restless or tired and without energy, or have difficulty breathing and eating.
When to see a doctor
See your doctor if you have difficulty breathing, chest pain, persistent fever of 102 F (39 C) or higher, or persistent cough, especially if you’re coughing up pus.
It’s especially important that people in these high-risk groups see a doctor:
- Adults older than age 65
- Children younger than age 2 with signs and symptoms
- People with an underlying health condition or weakened immune system
- People receiving chemotherapy or taking medication that suppresses the immune system
For some older adults and people with heart failure or chronic lung problems, pneumonia can quickly become a life-threatening condition.
Many germs can cause pneumonia. The most common are bacteria and viruses in the air we breathe. Your body usually prevents these germs from infecting your lungs. But sometimes these germs can overpower your immune system, even if your health is generally good.
- Bacteria-like organisms. Mycoplasma pneumoniae also can cause pneumonia. It typically produces milder symptoms than do other types of pneumonia. Walking pneumonia is an informal name given to this type of pneumonia, which typically isn’t severe enough to require bed rest.
- Fungi. This type of pneumonia is most common in people with chronic health problems or weakened immune systems, and in people who have inhaled large doses of the organisms. The fungi that cause it can be found in soil or bird droppings and vary depending upon geographic location.
- Viruses, including COVID-19. Some of the viruses that cause colds and the flu can cause pneumonia. Viruses are the most common cause of pneumonia in children younger than 5 years. Viral pneumonia is usually mild. But in some cases it can become very serious. Coronavirus 2019 (COVID-19) may cause pneumonia, which can become severe.
Pneumonia can affect anyone. But the two age groups at highest risk are:
- Children who are 2 years old or younger
- People who are age 65 or older
Other risk factors include:
- Being hospitalized. You’re at greater risk of pneumonia if you’re in a hospital intensive care unit, especially if you’re on a machine that helps you breathe (a ventilator).
- Chronic disease. You’re more likely to get pneumonia if you have asthma, chronic obstructive pulmonary disease (COPD) or heart disease.
- Smoking. Smoking damages your body’s natural defenses against the bacteria and viruses that cause pneumonia.
- Weakened or suppressed immune system. People who have HIV/AIDS, who’ve had an organ transplant, or who receive chemotherapy or long-term steroids are at risk.
To help prevent pneumonia:
- Get vaccinated. Vaccines are available to prevent some types of pneumonia and the flu. Talk with your doctor about getting these shots. The vaccination guidelines have changed over time so make sure to review your vaccination status with your doctor even if you recall previously receiving a pneumonia vaccine.
- Make sure children get vaccinated. Doctors recommend a different pneumonia vaccine for children younger than age 2 and for children ages 2 to 5 years who are at particular risk of pneumococcal disease. Children who attend a group child care center should also get the vaccine. Doctors also recommend flu shots for children older than 6 months.
- Practice good hygiene. To protect yourself against respiratory infections that sometimes lead to pneumonia, wash your hands regularly or use an alcohol-based hand sanitizer.
- Don’t smoke. Smoking damages your lungs’ natural defenses against respiratory infections.
- Keep your immune system strong. Get enough sleep, exercise regularly and eat a healthy diet.