Family Returns from Costa Rica with Histoplasmosis Cases
A recent report outlines how 12 members of a US family who visited a bat-inhabited cave in Costa Rica linked to a past histoplasmosis outbreak came back with confirmed or probable cases of the disease.
Histoplasmosis mainly impacts the lungs and arises from inhaling Histoplasma spores found in disturbed soil rich in bat guano or bird droppings. While most people show no symptoms, infants and individuals with compromised immune systems can experience severe, even chronic, illness if untreated.
In a study released last week in Morbidity and Mortality Weekly Report, a team from the US Centers for Disease Control and Prevention (CDC) looked into a cluster of suspected histoplasmosis cases among family members from Georgia, Texas, and Washington state, who traveled in December 2024 and January 2025.
Travel Details Spark Concerns
The family, consisting of 13 members, spent seven days in Costa Rica. On December 24, 12 of them toured the Venado Caves, a well-known site in the Alajuela province, near Nicaragua’s southern border. Among them, six were adults aged 42 to 49 and six were children aged 8 to 16.
During the two-hour tour, all reported encountering bats and coming into contact with bat droppings while navigating through tight spaces. They experienced mild to moderate sickness upon returning home, about 8 to 19 days later. Five adults and one child sought medical attention without mentioning their recent travel. Notably, the family member who didn’t visit the cave remained healthy.
Common symptoms included headache, malaise, fever, night sweats, muscle aches, and both respiratory and gastrointestinal issues. The investigation found no other activities that could have exposed the family to Histoplasma. Four members underwent tests for fungal antigens, two of which returned positive for the Histoplasma capsulatum species complex.
Three patients received antibiotics, two were administered corticosteroids, and one got a cough suppressant. One adult was referred to an emergency department after abnormal chest X-ray results raised concerns about lung cancer; that patient was given antifungal medication.
It was only the day after admission that healthcare workers, upon hearing about the recent travel, began to suspect histoplasmosis. On January 17, a Georgia physician specializing in infectious diseases alerted the CDC about the cases.
The cave had previously been associated with a histoplasmosis outbreak in 1998 and 1999, which affected 51 people.
Recovery of Patients
On January 21, 2025, the CDC kicked off a multi-state investigation in collaboration with the Georgia Department of Public Health, the Texas Department of State Health Services, and the Washington State Department of Health.
The researchers pointed out that antigen testing for all four patients occurred within one month of symptom onset, which is generally optimal. However, the sensitivity of these tests may be lower for individuals with mild disease.
One patient tested positive for both the antigen and complement fixation antibody tests. Besides the patient with suspicious radiographic results for lung cancer, another individual had abnormal x-rays showing nodules and opacities typical of histoplasmosis.
Family members were classified as having confirmed (1), probable (8), or suspected (3) histoplasmosis, following guidelines from the Council of State and Territorial Epidemiologists. By day 28 post-exposure, all sick family members had either fully recovered or showed signs of improvement, indicating mild or moderate histoplasmosis.
Concerns Over Treatment
The CDC sent out notifications to health departments to help identify additional cases of histoplasmosis and is collaborating with the US Embassy in Costa Rica to include information about the risks on Venado Caves’ tour waiver forms.
Currently, the Venado Caves tour website mentions that the cave houses a bat colony, and guests will receive masks, but it fails to warn visitors about histoplasmosis risks.
On March 18, the US Embassy issued a health alert, highlighting the potential for contracting histoplasmosis while caving, emphasizing that exposures at Venado Caves might still be ongoing.
Delays in diagnosing histoplasmosis are common, and treatment guidelines primarily advocate for antifungal medications in severe cases. The researchers emphasized that antibiotics are ineffective, and corticosteroids could worsen fungal infections. This suggests that fungal infections were not initially considered in the illness of some affected family members.
“Clinicians should keep fungal infections in mind when diagnosing patients with respiratory symptoms after caving or similar activities associated with histoplasmosis risk and report any suspected cases to local health authorities,” they concluded.
