Clinical and Public Health Microbiology

Fungi and Global Catastrophic Biorisks

In an opinion piece published in Health Security, author Arturo Casadevall urges scientists and policymakers to remember the threats to human and animal health that can occur from widespread fungal infections instead of focusing exclusively on bacteria and viruses.

Casadevall notes that, although humans and most mammals are usually resistant to invasive fungal diseases, the source of this resistance is thought to be a combination of adaptive immunity and endothermy, or the difference between normal mammalian temperatures and the lower temperatures tolerated by most fungal species.  Because global warming is increasing the ability of fungi to survive at higher temperatures and medical treatments for a variety of conditions involve lowered immune defenses, this picture may change significantly in the near future.

Although fungal agents are high on the alarm lists of agricultural scientists, they tend to be ignored by policymakers and preparedness experts for the human population.  This may be because humans have never experienced a fungal plague equal to the Black Death, the global HIV/AIDS or flu pandemics, or the problems caused by the Ebola and Zika viruses.  This does not hold true for other species.

Fungal pathogens can quickly demolish entire ecosystems.  Currently numerous amphibian species are dying as a result of a chytrid fungus; North American bats are being decimated by fungal white nose disease, which is new to the Americas; and salamanders, turtles, and snakes have been dying off in large numbers from new fungal disorders.

In the human realm, immunological impairments from HIV/AIDS have promoted cryptococcal pneumonia, candidiasis, and histoplasmosis, and the newly evolved Candida auris is causing severe systemic disease in healthcare facilities that is resistant to all three classes of major antifungal drugs.

The blind spot about fungal threats also means that labs that are working on important pathogenic fungi cannot apply for biodefense money because the organisms they address are not on the NIH Priority Agents list or the List of Select Agents put together by the Department of Health and Human Services (HHS).

Casadevall reminds us of the old adage that generals often prepare to fight the last war.  Since the analysis of biological threats is heavily weighted towards viral and bacterial risks we already know about, future global catastrophic biorisks that involve fungi may be our future wars and may find us completely unable to defend ourselves.

For more information, go to Health Security 15(4), 2017; DOI: 10.1089/hs.2017.0048.