Fungal pneumonia is not contagious in the way most people worry about. You cannot catch it from someone who is sick by being in the same room, sharing utensils, or through coughing and sneezing. Nearly all fungal pneumonias come from breathing in spores that exist naturally in soil, air, and decaying organic matter. There is one notable exception, though, worth understanding.
How People Actually Get Fungal Pneumonia
Instead of spreading person to person, fungal pneumonia starts when you inhale microscopic spores from the environment. These spores are everywhere. Aspergillus, one of the most common culprits, has roughly 180 known species, and its spores float through both indoor and outdoor air constantly. Most healthy people breathe them in regularly without ever getting sick. The infection takes hold when someone’s immune system can’t clear the spores before they establish themselves in the lungs.
The three main types of community-acquired fungal pneumonia in the United States are Valley fever (caused by Coccidioides in soil), histoplasmosis (caused by Histoplasma in soil contaminated with bird or bat droppings), and blastomycosis (caused by Blastomyces in moist soil). All three follow the same pattern: spores live in the ground, get kicked into the air by wind or digging, and enter the lungs of whoever happens to breathe them in. None of these spread from one person to another.
The One Exception: Pneumocystis Pneumonia
Pneumocystis pneumonia, often called PCP, breaks the rule. This fungal lung infection, caused by Pneumocystis jirovecii, does spread from person to person through the air. Some healthy adults carry the fungus in their lungs without symptoms and can pass it to others, including people with weakened immune systems. PCP is rare and almost exclusively affects people with severely compromised immunity, particularly those with untreated HIV/AIDS. For the general population, the risk of catching PCP from a carrier is essentially zero because a functioning immune system handles the fungus without difficulty.
Where These Fungi Live
Your risk depends partly on geography. Valley fever is concentrated in the desert Southwest. Southern Arizona (including Phoenix and Tucson) and California’s southern San Joaquin Valley report the highest rates, though the fungus has been found as far north as eastern Washington State and northeast Utah. Northern Mexico and parts of Central and South America also have significant Valley fever activity.
Histoplasmosis is most common in the Midwest and South-Central United States, particularly areas along the Ohio and Mississippi River valleys. The fungus thrives in soil enriched by bird and bat droppings, so old chicken coops, caves, and areas under large bird roosts are hotspots.
Blastomycosis clusters around the Great Lakes region, with hotspots in northern Minnesota and Wisconsin and western Ontario in Canada. A related species has been reported in small numbers in the western United States and Canada.
Who Is Most at Risk
Healthy people who inhale fungal spores typically fight off the infection without realizing it, or they develop mild flu-like symptoms that resolve on their own. Serious fungal pneumonia disproportionately affects people whose immune defenses are compromised. The CDC identifies several key risk factors:
- Cancer treatment: Chemotherapy and radiation lower white blood cell counts, reducing the body’s ability to fight fungal invaders.
- Organ and stem cell transplants: Anti-rejection medications deliberately suppress the immune system, creating an opening for fungal infections.
- HIV/AIDS: Especially when untreated, HIV destroys the immune cells needed to clear fungal spores.
- Chronic lung disease: Pre-existing damage to the lungs makes it easier for fungi to establish an infection.
- Long-term corticosteroid use: These medications reduce inflammation but also dial down immune function.
- Extended hospital stays: Being sick enough to require prolonged hospitalization already means a weakened immune system, and high doses of antibiotics can disrupt the body’s natural defenses against fungi.
People without these risk factors can still develop fungal pneumonia if they inhale a large concentration of spores, such as during excavation work in an endemic area or while cleaning out a bat-infested building. But for most healthy individuals, the body handles routine spore exposure without trouble.
How Fungal Pneumonia Is Treated
Treatment relies on antifungal medications, and the duration varies widely depending on the type and severity. Mild cases in otherwise healthy people sometimes resolve without treatment at all. More serious infections typically require weeks to months of antifungal therapy. Invasive aspergillosis, for example, often involves at least several weeks of treatment, while chronic forms of aspergillosis may need six months or longer. Certain aggressive fungal infections like mucormycosis can require treatment lasting months, with some courses extending well beyond a year in severe cases.
The three main classes of antifungal drugs work differently, giving doctors options when one type isn’t effective or causes side effects. Treatment usually starts with a stronger intravenous form in the hospital for severe cases, then transitions to oral medication that you take at home for the remainder of the course.
Reducing Your Exposure
Since fungal pneumonia comes from the environment rather than other people, prevention centers on limiting spore inhalation, especially if you have a weakened immune system or live in an area where these fungi are endemic.
If you work outdoors or do activities that disturb soil, practical steps include stopping work during dust storms or high winds, wetting soil before digging to suppress dust, and staying upwind of excavation sites. For histoplasmosis specifically, preventing the buildup of bird or bat droppings around buildings and using dust suppression when cleaning contaminated areas makes a significant difference. A properly fitted NIOSH-approved respirator offers protection against all three major endemic fungal infections during high-risk activities like construction, demolition, or cave exploration.
People with compromised immune systems should consider avoiding activities that involve disrupting soil altogether, particularly in endemic regions. Even something as routine as gardening or yard work can stir up enough spores to pose a risk when your body can’t mount a normal defense.