How common is histoplasmosis?
In the United States, an estimated 60% to 90% of people who live in areas surrounding the Ohio and Mississippi River valleys (where Histoplasma is common in the environment) have been exposed to the fungus at some point during their lifetime.1 One study calculated the incidence of histoplasmosis in adults aged 65 years and older in the U.S. to be 3.4 cases per 100,000 population.2 Rates were highest in the Midwest, with an estimated 6.1 cases per 100,000 population.2
Histoplasmosis is most common among people who have HIV/AIDS or a weakened immune system for another reason. It’s especially a problem in areas of the world where antiretroviral therapy (ART) is not widely available, because ART helps keep HIV-infected people from reaching the stage where they are most vulnerable to histoplasmosis and other opportunistic infections.3 In Latin America, for example, histoplasmosis is one of the most common opportunistic infections among people living with HIV, and approximately 30% of HIV/AIDS patients diagnosed with histoplasmosis die from it.4
Public health surveillance for histoplasmosis
Histoplasmosis is reportable in the following states and US territories: Alabama, Arkansas, Delaware, Illinois, Indiana, Kentucky, Michigan, Minnesota, Mississippi, Nebraska, Pennsylvania, Puerto Rico, Rhode Island, and Wisconsin. Check with your local, state, or territorial public health department for more information about disease reporting requirements and procedures in your area.
Although most cases of histoplasmosis are not associated with outbreaks, histoplasmosis outbreaks linked to a common source do occasionally occur. Common-source histoplasmosis outbreaks often involve activities that disrupt soil, especially soil that contains bird or bat droppings. Examples of these types of activities include: construction,5 renovation,6 exploring caves,7 tilling soil,8 and cleaning up bird roosting sites.9 If you live in an area where Histoplasma is common in the environment, contact your local or state health department for the most up-to-date information about outbreaks.
Deaths due to histoplasmosis
One study of patients who were hospitalized for histoplasmosis in the U.S. estimated the crude mortality rate to be approximately 5% for children and 8% for adults.10 Another study found a six-month mortality rate of 4% among patients with symptomatic histoplasmosis.11 The overall mortality rate for histoplasmosis is likely lower than these estimates because these studies did not include patients who had less severe forms of the infection.