Histoplasmosis can remain hidden or dormant in the body for months or years after the initial exposure. While symptoms typically appear 3 to 17 days after breathing in the fungus, the infection can become latent, especially in people with weakened immune systems, and reactivate later.


From the CDC (US Center for Disease Control)
KEY POINTS


Histoplasmosis is an infection caused by a fungus called Histoplasma.
Activities that involve plant matter or disturb soil, particularly soil that contains bird or bat droppings, can increase risk for histoplasmosis.


Certain groups of people are at higher risk for developing severe histoplasmosis.

Overview

Anyone can get histoplasmosis if they've been in an area where Histoplasma lives in the environment. Breathing in spores from the fungus can cause illness but most of the time people do not get infected. It cannot spread between people or between people and animals.

Where it is circulating in the environment, it is difficult to avoid breathing in fungal spores. Avoiding activities that involve plant matter or disturb soil, particularly soil that contains bird or bat droppings, reduces risk for histoplasmosis.

Who is at risk

Populations at risk

Certain groups of people are at higher risk for getting histoplasmosis and for more severe infections, including people who:

Have HIV/AIDS.
Receive an organ transplant.
Take medications such as corticosteroids or TNF-inhibitors.
Are exposed to large amounts of the fungus such as:
Outdoor workers
Construction workers
Farmers, especially if handling or cleaning up after chickens.
Adults over the age of 55 and infants are more at risk for histoplasmosis.

Risk factors
The chances of getting histoplasmosis symptoms rise with the number of spores you breathe in. People more likely to be exposed to the spores include:
Farmers.
Pest control workers.
Poultry keepers.
Construction workers.
Roofers.
Landscapers and gardeners.
Miners and cave explorers.
Demolition workers.
Oil and gas extraction workers.
People most at risk of severe infection
Children younger than age 2 and adults age 55 and older have weaker immune systems. Because of this, they're more likely to get the most serious form of the disease, called disseminated histoplasmosis. Other factors that can weaken the immune system include:
HIV or AIDS.
Cancer chemotherapy.
Corticosteroid medicines such as prednisone.
Medicines called tumor necrosis factor inhibitors, which often are used to control rheumatoid arthritis.
Medicines that prevent the body from rejecting a transplanted organ.