Summary Blastomycosis , coccidioidomycosis , and histoplasmosis are the most common endemic mycoses in North America. Exposure within focal endemic regions is often unavoidable, and patients are often unaware of activities that increase individual risk. These fungi have traditionally had distinct geographic distributions, although these regions are expanding and the organisms are probably much more widespread. They occupy a specific ecological niche in the environment and can cause disease in healthy hosts. After inhaling the infectious “spores ,” these fungal pathogens often survive macrophage ingestion and escape, and then replicate and produce clinical disease. |
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Climate change widens spread of valley fever and other fungal diseases beyond typical hotspots
Infectious disease expert George Thompson has been studying and treating fungal diseases for more than two decades. He monitors its spread, symptoms and relative risks. Lately, he’s been more concerned about a growing threat: the spread of disease-causing fungi outside their traditional hotspots.
In a commentary published in the Annals of Internal Medicine , Thompson and his co-author from the Centers for Disease Control and Prevention’s Fungal Diseases Branch, Tom Chiller, raised the alarm. They noted the increasing presence and emerging risks of three endemic fungal diseases: histoplasmosis, blastomycosis, and coccidioidomycosis (valley fever).
“These three fungal diseases generally inhabit specific regions of the U.S. conducive to their survival,” Thompson said. He is a professor at the UC Davis School of Medicine in the Department of Internal Medicine, Division of Infectious Diseases and the Department of Medical Microbiology and Immunology. “Recently, we are finding more cases of these diseases outside their known areas, taking doctors and patients by surprise.”
Fungal infections are an emerging global threat
Fungi are microorganisms that are found abundantly in nature. They include yeasts, molds, fungi and more. While most fungi are harmless to humans, some can cause diseases (known as mycoses) that could wreak havoc on patients and the healthcare system.
Recently, the World Health Organization (WHO) published its list of priority pathogenic fungi, identifying the fungi of most concern that can cause infections for which there is drug resistance or other treatment challenges. These pathogens are expected to create even more problems over the next decade.
Climate change increases the spread of fungal infections
Endemic fungi have traditionally had different geographical distributions. Climate changes in temperature and rainfall are affecting where these fungi thrive.
The authors noted the expanding regions that host endemic fungi. Valley fever, for example, was found in Nebraska, far east of its traditional hotspots in California and Arizona.
“The organisms are probably much more widespread than we originally thought. There is an increasing likelihood that physicians who are unfamiliar with these organisms will encounter them during their daily practice,” Thompson said.
Doctors often miss the diagnosis of fungal infection
The three endemic mycoses have many symptoms, such as fever, chills, cough, night sweats, and fatigue. They can also cause lung infections that mimic pneumonia. As such, they can be easily confused with more common viral and bacterial lung infections.
Current pneumonia guidelines from the American Thoracic Society and the Infectious Diseases Society of America do not offer specific testing or treatment recommendations for endemic mycosis. Most doctors may have little experience in recognizing and treating these fungal lung infections.
About 20% of pneumonia cases in some parts of California and Arizona are caused by valley fever. However, it usually takes more than three weeks after symptoms begin to get the correct diagnosis. It may take even longer to diagnose histoplasmosis and blastomycosis.
Fungal infections are also commonly diagnosed as bacterial. When this misdiagnosis occurs, the patient is prescribed antibiotics that are not effective for fungal diseases. This also exposes them to unnecessary medications and contributes to the rise of antimicrobial resistance in the community. The authors urged doctors to take a complete travel history and perform further tests to rule out a fungal infection before giving patients a second round of antibiotics.
“In regions where these fungal diseases thrive, clinicians should consider diagnosis and testing for mycoses in all patients with suggestive diseases,” Thompson recommended.
The authors identified several factors that could contribute to these delays in diagnosis and treatment. One is the variation in doctors’ knowledge about diagnosing and managing diseases. Another is the lack of point-of-care diagnostics. The panels typically used for the diagnosis of respiratory infections do not include endemic mycoses. Serum antibody and urinary antigen tests for endemic mycoses are usually available only in certain laboratories.
Action plan to address endemic mycoses
The authors see an opportunity to improve fungal diagnosis and treatment practices through improved surveillance and continued medical education about these regional infections. They suggested a multifaceted approach to assist with preventive efforts and timely recognition and treatment of these diseases. They ordered:
1) National surveillance and notification of endemic mycotic diseases in both humans and animals.
2) Educational efforts for patients and providers.
3) Inclusion of endemic mycoses in future pneumonia guidelines.
4) Development of diagnostic tools at the point of care.
5) Exploration of a vaccine against panendemic mycoses to prevent infection.
