Pigeons, herons, parakeets and other urban birds can carry fungi in their droppings that are capable of causing serious respiratory infections. The risk is associated with squares, parks and tree-filled urban areas where bird waste accumulates, dries and becomes particles that can be inhaled.
The problem goes far beyond visible dirt. A place may appear to be merely marked by bird waste, while the dried material can spread through the air as dust. People who spend time in those areas may not realize that the main concern is found in particles that cannot be seen.
Two fungi associated with bird waste
Two fungi stand out as the main agents of concern: Cryptococcus neoformans, which causes cryptococcosis, and Histoplasma capsulatum, which causes histoplasmosis. Both can be found in bird droppings accumulated on the ground in squares, parks and urban areas with trees.
Contamination occurs when particles from contaminated soil become airborne and are inhaled. These two infections are not transmitted from one person to another. In both cases, contamination occurs exclusively through inhalation of particles from contaminated soil.
The presence of birds in a park does not, by itself, describe the entire risk. The situation that requires more attention is the accumulation of droppings and the way those droppings dry. Once waste remains on the ground and dries, fungal particles can be lifted by movement or by dry sweeping.
Cryptococcosis and histoplasmosis differ
Cryptococcus neoformans is more closely associated with droppings from herons and pigeons. When the waste dries and turns into dust, the fungus can spread through the air and be inhaled. The resulting infection, cryptococcosis, first affects the lungs.
In severe cases, cryptococcosis can move to the central nervous system. For that reason, attention should not be limited to respiratory symptoms. An illness that begins in the lungs can become more serious when signs involving the nervous system appear.
Histoplasma capsulatum is found in soil enriched with droppings from several bird species. The species mentioned include parakeets, starlings and pigeons. The disease caused by this fungus, histoplasmosis, also begins in the lungs.
Histoplasmosis can be mistaken for pneumonia or tuberculosis. In tropical regions, its prevalence is significant. Because it resembles other respiratory illnesses, contact with areas where bird droppings accumulate is important information when compatible symptoms develop.
Although both diseases can begin in the lungs, they are not the same problem. One is associated with Cryptococcus neoformans, while the other is associated with Histoplasma capsulatum. The birds and soil conditions linked to them also differ in the description of the risk.
Who faces the greatest risk
Children who play in parks are especially vulnerable. They spend more time close to the ground, where the concentration of particles is higher, and their immune systems are still developing. Contact with areas where waste has accumulated can increase exposure to particles released as the droppings dry.
Older adults, pregnant people and those with diseases that affect immunity also face a greater risk of developing severe illness. The conditions mentioned include HIV, cancer treatment and the use of immunosuppressive drugs.
Urban sanitation workers can also face substantial exposure. Workers who sweep parks without respiratory protection are among the most exposed groups because dry sweeping raises precisely the particles that can carry the fungi.
In that setting, the cleaning method matters. Waste that has accumulated on the ground is already a concern, but dry sweeping can disperse the material and increase the amount of particles in the air. Respiratory protection is particularly important for people who perform this work.
Warning signs in the body
A dry cough that continues for more than two weeks after visiting areas with accumulated bird droppings deserves attention. A low-grade fever, tiredness and chest pain are also initial signs of both cryptococcosis and histoplasmosis.
These symptoms may seem nonspecific, especially because both infections begin in the lungs and one of them can be confused with pneumonia or tuberculosis. A cough that continues after contact with a contaminated square or park should not be ignored.
Some symptoms require urgent medical attention. Severe headache, a stiff neck or confusion may indicate that the fungus has reached the central nervous system. These signs can point to severe progression of cryptococcosis.
The connection with a contaminated area alone cannot identify which fungus is involved. Still, information about accumulated bird droppings and the duration of coughing, fever, tiredness or chest pain can be relevant when medical care is sought.
Practical ways to reduce exposure
Avoiding places with visible accumulations of bird droppings is the simplest measure. If it is necessary to pass through those areas, wearing a PFF2 or N95 mask significantly reduces the risk of inhaling particles.
Cleaning also requires care. Bird droppings should never be swept while dry. The correct approach is to moisten the material with water and sodium hypochlorite before removing it, preventing fungal particles from dispersing.
This recommendation is especially important for urban sanitation workers, who are among the people most exposed when they sweep parks without respiratory protection. Moistening the material before removal prevents cleaning from raising the dust that may carry the fungi.
Another measure is not feeding urban birds in squares. Providing food attracts more birds and increases the concentration of droppings in the area. Reducing that concentration helps prevent the accumulation of waste that can turn into airborne particles after drying.
Parks and squares are part of daily life for children, older adults and entire communities, but areas with visible bird waste require caution. Recognizing that the risk comes from invisible particles, rather than only from visible dirt, makes it possible to avoid exposure, pay attention to symptoms and clean contaminated material more safely.
Reporting: Anne Silva / Amazonia Mag
Editor, English Edition — Amazonia Mag
Anne Silva is the editor of Amazonia Mag, the English-language edition of Revista Amazônia. She curates, translates and adapts the outlet's science and environment coverage for an international audience, reporting on Amazon wildlife, flora, rivers, climate and research. Every story she edits is grounded in peer-reviewed studies, official data and on-the-ground reporting from the Revista Amazônia newsroom in Belém, Pará, Brazil. More by Anne Silva →