Twelve members of one family, three states, and a cave in Costa Rica

Histoplasmosis is a fungal infection that mainly affects the lungs, caused
by Histoplasma organisms found in soil contaminated with **bird or bat
droppings**. It is often misdiagnosed.

The CDC was notified of a cluster of suspected cases affecting **12 members of
an extended family from three US states** — Georgia, Texas and Washington.

They had all visited Venado Caves in Costa Rica, the site of a previous
histoplasmosis outbreak associated with contact with bat droppings, and the
likely source here.

Four family members were tested for fungal antigen, and **two returned
positive results for the Histoplasma capsulatum species complex**.

Why this one was found and others are not

Twelve people fell ill across three states with a respiratory illness that is
often misdiagnosed. In ordinary circumstances that is twelve unconnected
patients, each seen by a different clinician, most of them diagnosed with
something else.

It became a recognisable cluster for one reason: **they were a family, and
they talked to each other.** Nothing in the health system connected a case in
Georgia to a case in Washington.

Which means the same exposure happening to twelve strangers on the same tour
would, in all likelihood, have produced no cluster at all — twelve separate
diagnoses of pneumonia.

What clinicians are asked to do

Consider histoplasmosis in patients with compatible signs and symptoms:
fever, malaise, cough, headache, chest pain, chills and myalgias.

And the step that actually makes the diagnosis possible:

**Obtaining a detailed travel and activity history is necessary to identify
exposure to bat or bird droppings in caves or elsewhere.**

Not "have you travelled" — what did you do there. A cave tour is the kind of
activity nobody volunteers when describing a holiday to a doctor treating what
looks like a chest infection.

*Source: Ghai RR, Sajewski ET, Blass M, et al. Cave-Associated Histoplasmosis
Outbreak Among Travelers Returning from Costa Rica — Georgia, Texas, and
Washington, December 2024–January 2025. MMWR, Centers for Disease Control and
Prevention.*