The Centers for Disease Control and Prevention (CDC) has launched a nationwide probe into 12 members of an extended family who contracted histoplasmosis after a recent trip to Costa Rica. Pulmonary disease caused by the fungus Histoplasma capsulatum was suspected on December 24, 2024, during the exposure to the cave tour.
All the affected individuals included adults aged 42 to 49 years old and children aged 8 to 16, from families in Georgia, Texas, and Washington. They visited Venado Caves, which had been the site of a histoplasmosis outbreak in the late 1990s. All 12 explorers were believed to have come into close contact with bat droppings, which are the main source of fungal spores.
Symptoms appeared between 8 and 19 days after individuals returned from the cave. Patients frequently complained of fever, headache, tiredness, night sweats, aching muscles, and trouble with their respiratory or digestive organs. The only family member who did not enter the cave remained healthy.
The CDC and the health departments of Georgia, Texas, and Washington began the investigation on January 21. Authorities described the event as a matter of public health rather than a scientific research endeavor. While the symptom severity varied, every affected person showed signs of recovery or had recovered by 28 days after exposure.
Six family members sought medical care, and no one at first volunteered their travel history. This led to misdiagnoses and inappropriate treatments with antibiotics, corticosteroids, and cough suppressants. One adult was hospitalized when chest imaging suggested possible lung cancer. Based on the existing travel history, the working diagnosis was revised to histoplasmosis, and an antifungal therapy was prescribed. The patient’s management plan was later modified to itraconazole.
Two out of four people assessed tested positive for Histoplasma antigen, which carries a risk of false negatives in mild cases among healthy individuals. One patient had additional confirmation through repeat positive antibody tests. Lung imaging conducted for two patients reported chest X-rays suggested lung lesions consistent with advanced primary pulmonary histoplasmosis.
Using Council of State and Territorial Epidemiologists (CSTE) criteria, one case was classified as confirmed, eight were categorized as probable, and three of the cases were deemed suspected. Categorization as confirmed requires clinical and laboratory validation. Probable and suspected cases were epidemiologically linked to the confirmed patient.
Following the outbreak, the CDC put out an Epidemic Information Exchange (Epi-X) alert. It partnered with the Ministry of Health in Costa Rica and the US Embassy to reinforce traveler alert notifications. An advisory was issued in March 2025, warning travellers of the possible dangers of cave exploration in this area.
Histoplasmosis is often under-analysed, especially in travellers with non-specific mild symptoms. Health experts have raised concerns that both antibiotics and steroids can worsen a fungal infection and highlighted the importance of diagnosing a fungal disease in persons with unexplained respiratory illness after cave exploration activities.
Clinicians should inquire about travel history and report suspected cases to public health authorities to strengthen detection patterns and public health response in outbreak settings.
References: 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 Morb Mortal Wkly Rep. 2025;74(17):289–292
