Pneumonia: Causes, Symptoms, Diagnosis & Treatment (2024)

What is pneumonia?

Pneumonia is an infection in your lungs caused by bacteria, viruses or fungi. Pneumonia causes your lung tissue to swell (inflammation) and can cause fluid or pus in your lungs. Bacterial pneumonia is usually more severe than viral pneumonia, which often resolves on its own.

Pneumonia can affect one or both lungs. Pneumonia in both of your lungs is called bilateral or double pneumonia.

What’s the difference between viral and bacterial pneumonia?

While all pneumonia is inflammation caused by an infection in your lungs, you may have different symptoms depending on whether the root cause is a virus, bacteria or fungi.

Bacterial pneumonia tends to be more common and more severe than viral pneumonia. It’s more likely to require a hospital stay. Providers treat bacterial pneumonia with antibiotics. Viral pneumonia causes flu-like symptoms and is more likely to resolve on its own. You usually don’t need specific treatment for viral pneumonia.

What are the types of pneumonia?

We categorize pneumonia by which pathogen (virus, bacteria or fungi) caused it and how you got it — community-acquired, hospital-acquired or ventilator-associated pneumonia.

Community-acquired pneumonia (CAP)

When you get pneumonia outside of a healthcare facility, it’s called community-acquired pneumonia. Causes include:

• Bacteria: Infection with Streptococcus pneumoniae bacteria, also called pneumococcal disease, is the most common cause of CAP. Pneumococcal disease can also cause ear infections, sinus infections and meningitis. Mycoplasma pneumoniae bacteria causes atypical pneumonia, which usually has milder symptoms. Other bacteria that cause CAP include Haemophilus influenza, Chlamydia pneumoniae and Legionella (Legionnaires’ disease).
• Viruses: Viruses that cause the common cold, the flu (influenza), COVID-19 and respiratory syncytial virus (RSV) can sometimes lead to pneumonia.
• Fungi (molds): Fungi, like Cryptococcus, Pneumocystis jirovecii and Coccidioides, are uncommon causes of pneumonia. People with compromised immune systems are most at risk of getting pneumonia from a fungus.
• Protozoa: Rarely, protozoa like Toxoplasma cause pneumonia.

Hospital-acquired pneumonia (HAP)

You can get hospital-acquired pneumonia (HAP) while in a hospital or healthcare facility for another illness or procedure. HAP is usually more serious than community-acquired pneumonia because it’s often caused by antibiotic-resistant bacteria, like methicillin-resistant Staphylococcus aureus (MRSA). This means HAP can make you sicker and be harder to treat.

Healthcare-associated pneumonia (HCAP)

You can get HCAP while in a long-term care facility (such as a nursing home) or outpatient, extended-stay clinics. Like hospital-acquired pneumonia, it’s usually caused by antibiotic-resistant bacteria.

Ventilator-associated pneumonia (VAP)

If you need to be on a respirator or breathing machine to help you breathe in the hospital (usually in the ICU), you’re at risk for ventilator-associated pneumonia (VAP). The same types of bacteria as community-acquired pneumonia, as well as the drug-resistant kinds that cause hospital-acquired pneumonia, cause VAP.

Aspiration pneumonia

Aspiration is when solid food, liquids, spit or vomit go down your trachea (windpipe) and into your lungs. If you can’t cough these up, your lungs can get infected.

How can I tell if I have pneumonia versus the common cold or the flu?

It can be difficult to tell the difference between the symptoms of a cold, the flu and pneumonia, and only a healthcare provider can diagnose you. As pneumonia can be life-threatening, it’s important to seek medical attention for serious symptoms that could be signs of pneumonia, such as:

• Congestion or chest pain.
• Difficulty breathing.
• A fever of 102 degrees Fahrenheit (38.88 degrees Celsius) or higher.
• Coughing up yellow, green or bloody mucus or spit.

Who is most at risk of getting pneumonia?

You’re at an increased risk of pneumonia if you:

• Are over the age of 65 and or under the age of 2.
• Are living with a lung or heart condition. Examples include cystic fibrosis, asthma, chronic obstructive pulmonary disease, emphysema, pulmonary fibrosis or sarcoidosis.
• Are living with a neurological condition that makes swallowing difficult. Conditions like dementia, Parkinson’s disease and stroke increase your risk of aspiration pneumonia.
• Are in the hospital or at a long-term care facility.
• Smoke.
• Are pregnant.
• Have a weakened immune system. You might have a weakened immune system if you’re on chemotherapy, are an organ transplant recipient, are living with HIV/AIDS or are taking medications that suppress your immune system.

How common is pneumonia?

Anyone can get pneumonia. It’s a common illness, with millions of people diagnosed each year in the United States. About 55,000 people die each year of pneumonia in the U.S. It’s the most common cause of death in developing countries.