What Is Pneumonia? 5 Warning Signs to Watch For

Whether caused by viruses, fungi or bacteria, this lung infection can turn serious — especially in older adults

Michelle Crouch,

Updated February 18, 2025

AARP

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Published November 02, 2021

/ Updated February 18, 2025

woman home wrapped in a blanket coughing and holding a cup of tea

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It’s pretty common to develop a cough or an upper respiratory infection in the winter. Most of the time you get over it quickly. But sometimes a winter illness can develop into pneumonia, a lung infection that is particularly dangerous for older adults.

In a typical year, about 1.4 million Americans go to the emergency room with pneumonia and more than 41,000 people die of the disease, according to the Centers for Disease Control and Prevention (CDC).

Pneumonia can cause severe illness in people of any age, but children under age 5 and older adults are the most vulnerable. A 2022 National Health Statistics report found about 5 percent of patients aged 18 to 44 died while hospitalized for pneumonia; that share jumped to 11 percent among patients 65 and older.

People who smoke, have weak immune systems or suffer from chronic conditions such as lung disease or heart disease are at higher risk for complications from the illness.

Pneumonia causes and diagnosis

Pneumonia can be caused by bacteria, fungi or viruses, including the ones that cause the flu, respiratory syncytial virus (RSV) and COVID-19.

The vast majority of people with pneumonia have bacterial infections, but recent data suggests that viruses cause more cases than doctors previously realized. Bacterial pneumonias tend to be more severe than those caused by viruses.

It’s not unusual to develop bacterial pneumonia while your body is fighting a viral infection, says Todd Rice, M.D., professor of medicine and director of the medical intensive care unit at Vanderbilt Medical Center in Nashville, Tennessee.

Pneumonia is diagnosed with a chest X-ray or CT scan. Your doctor may also send your blood and a mucus sample to a lab for a culture to try to determine what type of bacteria or virus is the culprit.

5 pneumonia warning signs and symptoms

Pneumonia symptoms can be mild or severe. They tend to be similar to those of a cold or flu, but they last longer and may get worse over time. Here are some common symptoms.

Productive cough. You will be “coughing up lots of nasty stuff,” says Charles Bregier, M.D., an emergency medicine physician and medical director at Novant Health in Charlotte, North Carolina. The sputum often has a yellow, green or gray look.
Fever. Fever and chills are signs that your body is fighting the infection. But the absence of a fever doesn’t necessarily rule out pneumonia, especially in those age 65 and older. (See sidebar.)
Shortness of breath. You may have trouble catching your breath when walking or talking, or feel like you’re breathing faster than normal.
Chest pain. You may experience sharp or stabbing chest pain that hurts more when you take a deep breath or cough.
Dizziness or delirium. Some older adults with pneumonia may experience a change in cognition or awareness, says Sarina Sahetya, M.D., a pulmonologist and intensivist at Johns Hopkins Medicine. “If someone comes into the hospital and says their loved one is confused,” she says, “that’s a red flag for us to start looking for infection.”

When to call a doctor

What to know about pneumonia and body temperature

A fever is often associated with pneumonia because the body is fighting an infection, but that’s not always the case in older adults, says Sahetya.

Sometimes older adults with pneumonia actually develop a low body temperature — below 97 degrees Fahrenheit, she notes.

“It has to do with how your immune system is responding to infection,” she says. “In people who are older, who tend to have weaker immune systems or who are immunosuppressed, instead of getting the immune system revved up, the infection actually can cause low temperatures.”

It’s important to reach out to your doctor right away if you suspect pneumonia, especially if the patient is in a higher-risk group. Because dangerous complications can occur, starting treatment early can be critical.

If at any time you are experiencing shortness of breath or persistent chest pain, you should seek immediate care by going to the emergency room, Rice says.

How to prevent pneumonia

How can you protect yourself and your loved ones from pneumonia?

Start by taking the same steps you use to protect yourself against other illnesses: wash your hands frequently, avoid touching your nose and mouth, and stay away from those who are coughing and sneezing. To keep your immune system strong, make sure you get enough sleep, exercise regularly and eat a healthy diet.

Getting the influenza, RSV and COVID-19 vaccines will help protect you from pneumonia caused by those viruses. There’s also a vaccine that helps protect against pneumococcal disease, which can lead to pneumococcal pneumonia, the most common type of bacterial pneumonia in the U.S.

The pneumococcal vaccine is recommended for adults 50 and older and others with certain health conditions that increase their risk for serious illness.

Editor's note: This story, first published Nov. 2, 2021, has been updated to include new information.

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Michelle Crouch is a contributing writer who has covered health and personal finance for some of the nation’s top consumer publications. Her work has appeared in Reader’s Digest, Real Simple, Prevention, The Washington Post and The New York Times.