5 major causes of pneumonia and how you can prevent it

• You can get pneumonia through bacterial, fungal, or viral infections.
• You can also get aspiration pneumonia, which is when you inhale food, or hospital-acquired pneumonia.
• To prevent pneumonia, get the flu shot, wash your hands, and stop smoking.

Pneumonia is a lung infection that can be caused by bacteria, fungi, or viruses. Symptoms of pneumonia include shortness of breath, fever, and cough.

Here are the five major causes of pneumonia and how you can prevent the condition.

Bacteria

Bacterial pneumonia is any pneumonia caused by bacteria and is usually treated with antibiotics. More than 900,000 Americans develop bacterial pneumonia each year.

The most common cause of bacterial pneumonia in the US is Streptococcus pneumoniae, which is usually found in the nose and throat. The bacteria spreads through drops of saliva or mucus when people cough or sneeze. While many of us carry this germ without becoming ill, it often causes pneumonia in older people, young children, and smokers or those with weaker immune systems due to either illness or medication.

Although rarer than strep pneumonia, other bacteria can cause the condition, too. This is known as atypical pneumonia, or walking pneumonia. Walking pneumonia often has milder symptoms and does not require bed rest.

Fungi

The spores of certain fungi, if inhaled in large doses, can also lead to pneumonia. In 2011, more than 20,000 cases of fungal pneumonia were reported in the US, making this type of pneumonia less common.

Fungi that can cause pneumonia include:

• Histoplasmosis, which is common to the Ohio and Mississippi River Valleys.
• Cryptococcus, which is found in bird droppings nationally.
• Coccidioidomycosis, which lives in the soil of the Southwest.

Farmers, agricultural workers, and landscapers are at a higher risk for developing fungal pneumonia because they work in close contact with soil that can carry these fungi.

Additionally, the fungus pneumocystis jirovecii can lead to a serious condition called pneumocystis pneumonia (PCP) in immunocompromised people, such as people with HIV or recent organ recipients. Fungal pneumonia can be treated with antifungal medication.

Viruses

Some viruses, such as those that cause pink eye or the flu, can also cause pneumonia. Viral pneumonia accounts for about one in every three pneumonia cases, although these cases tend to be milder and shorter than bacterial pneumonia since there is less inflammation.

Respiratory illnesses, like the flu or COVID-19, can lead to pneumonia by causing inflammation and fluid build-up in the lungs, making it more difficult to breathe.

There are few to no treatments for most viruses that cause pneumonia, meaning patients must wait for the infection to pass. However, if doctors believe that a flu virus is to blame, they may prescribe some antiviral therapies or other medications to help ease breathing.

Hospital-acquired pneumonia

Hospital-acquired pneumonia refers to any pneumonia contracted 48 hours or more after hospital admission. The condition is serious not only because patients' immune systems may be weakened from other diseases, but also because the bacteria found at hospitals can be resistant to antibiotics.

Causes of hospital-acquired pneumonia include:

• Healthcare workers may spread it with their hands, clothes, or instruments as they move from one patient to another.
• Poor oral hygiene, which means it is more likely bacteria in saliva enters the lungs while breathing, talking, or eating, says Karen Giuliano, an associate professor of medical product innovation and development at the University of Massachusetts. This is called microaspiration.

Microaspirations can become dangerous in a hospital-setting because patients - and their mouths - are in contact with not only more bacteria, but different kinds than we would experience at home. Meanwhile, oral hygiene among hospitalized patients tends to be a low priority as healthcare workers focus on the problems for which patients were admitted - increasing the levels of bacteria in their mouths, she says.

Making sure people have access to good oral hygiene, like brushing their teeth, during their hospital stays may reduce the risk of hospital-acquired pneumonia.

Ventilator-associated pneumonia

This is another form of pneumonia that occurs when people on breathing machines contract pneumonia via germs entering their breathing tube. It is categorized as a distinct form of pneumonia separate from hospital-acquired pneumonia, despite its hospital setting.

Aspiration pneumonia

Aspiration pneumonia is a type of pneumonia that occurs when food or liquid is inhaled into the lungs, causing an infection. The phenomenon is one of the most common causes of pneumonia in long-term care facility patients. Although cases of the condition have declined in roughly the last decade, it remains a particular risk for patients over the age of 65.

Who is at risk for pneumonia?

Certain people are at a greater risk of developing pneumonia. At-risk groups include:

• People older than 65
• Children younger than two
• People with weaker immune systems due to illness, like diabetes and cancer, as well as those with chronic lung conditions
• Smokers
• People on medications like chemotherapy and long-term steroids
• Patients in hospital, including those on ventilators
• People living with HIV, especially those not yet on antiretroviral therapy or whose HIV is poorly controlled

How to prevent pneumonia

You can take several steps to reduce your risk of pneumonia, including:

• Those at risk should receive the pneumococcal conjugate vaccine or pneumococcal polysaccharide vaccine which both protect against streptococcus viral pneumonia
• Anyone over the age of six months should also get an annual flu shot
• Stop smoking
• Wash your hands frequently
• Manage chronic conditions such as asthma, heart disease, and diabetes
• People with HIV should begin antiretroviral treatment
• Hospital patients should try to walk as soon as possible, says Giuliano, as this can increase their lung capacity and prevent fluid build-up

Additionally, anyone being admitted to the hospital should make sure to pack their own oral hygiene kit. Giuliano suggests packing:

• A high-quality, soft-bristled toothbrush
• Toothpaste that contains substances such as fluoride to help breakdown plaque
• Alcohol-free antiseptic mouth rinse

Insider's takeaway

You can get pneumonia from bacteria, viruses, or fungi. Pneumonia can affect the young and old, but people who are hospitalized or have weaker immune systems because of age or underlying health conditions are more at risk.

Vaccinations, frequent handwashing, and managing chronic illnesses can help reduce your risk of pneumonia. Hospitalized patients should also be sure to practice good oral hygiene while in facilities and try to be as mobile as possible.

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