The Possibility of a Fungus-caused Pandemic: Separating Fact from Fiction

Since the beginning of the SARS-CoV-2 health contingency, much has been said about the possibility of a new pandemic shortly due to the effects of global warming. This phenomenon is a fact, and its effects seem difficult to stop in the short term. But not only are climates changing but so are the places where different species live.

A fungus-caused pandemic is a new possibility that the general public hasn't given much thought to, according to the new science fiction series "The Last of Us". Among the things that make pathogenic fungi unique are their ability to infect people with weak immune systems, their resistance to treatment, and their difficulty in making vaccines. In addition, opportunistic infections often have a very poor prognosis in frail patients.

Are mushrooms a cause for concern for a new pandemic, as the series suggests?

One of the things we have learned from science fiction is that it sometimes acts as a bridge between the present and the future. From Isaac Asimov's books, for example, we have gotten some predictions of what was going to happen in our days. However, it is important to understand that some things that are foreshadowed exceed reality and fact. Cordyceps sp. is a species-specific insect pathogen that generally inhabits tropical climates; it does not generate disease in humans.

But it should be clear that mutations happen often in living things, but not all of them are good enough to survive. This is one of the ways that living things can adapt to their surroundings. It is also one of the things that have led to the variety of life on Earth. In this case, it's important to note that this kind of change usually takes a long time and doesn't happen in a few years.

Mutations occur at different rates in different organisms. For example, fungi generally mutate slower than viruses and bacteria, approximately 100 million times less rapidly (10-8 to 10-10 substitutions per base pair per generation in Edwards and Rhodes, 2021), hence we see epidemics and pandemics more frequently due to viruses. Thus, it seems rational not to worry so much (but not to dismiss this possibility altogether), since they are ultimately the product of science fiction.

Are all fungi harmful to humans?

The reality is that fungi can be found everywhere: in the environment, in water, in food, and even in our bodies as part of the microbiota. They are essential for life on earth as we know it since they are organisms that decompose organic matter and play a very important role in the carbon and nitrogen cycles. People also use them to make medicines, foods like mushrooms, drinks like beer and fermented yogurt, bread, and aged cheeses, among other things. So, not all fungi can make people sick, and people shouldn't be so scared of them that they panic.

What about fungi that are already currently pathogenic for humans?

In the health field, it seems more urgent to worry about fungi that are indeed pathogenic and harm our health. We know that only a small number of fungi in the world are dangerous to humans. Body temperature is a major barrier to their spread (Sun et al., 2020).

Pathogenic fungi include dermatophytes (those that attack hair, skin, and nails), opportunistic fungi (e.g., Candida sp.), and systemic fungi (e.g., Histoplasma capsulatum). However, while some of these tend to generate infections that are no more than discomfort, pain, or cosmetic affection in immunocompetent subjects, others can cause life-threatening infections. Some strains of these have generated resistance to treatments, demonstrating their adaptability and potential health risk.

The World Health Organization (WHO) released a list of the most dangerous pathogenic fungi in December of last year. These fungi need more surveillance and testing in labs, more money for research, and public health interventions. So we already have disease-causing fungi to pay attention to.

Are there fungi of regional importance to which Sonorans should pay attention?

In Sonora, Coccidioides sp. is one of the fungi that we should pay attention to since it is endemic to the state and circulates in the environment. It is the pathogen that causes the so-called valley fever, an often asymptomatic disease that can sometimes cause flu-like symptoms or even pneumonia. This fungus is included in the WHO list of priority pathogens in the medium-risk category.

Since 1948, when Dr. Gaston Madrid wrote about cases of pulmonary coccidioidomycosis in Hermosillo, Sonora, we have known that Coccidioides sp. is in Sonora. But because this disease is no longer required to be registered, we don't know much about its spread in the population.

The most recent data we have is from Davila et al. (2018), who reported coccidioidin reactivity that was very similar to Gonzalez-Ochoa's record, 55.4%–63.9%, with seasonal variations throughout the year. From reports in the United States, we know that its frequency changes with the amount of rain and season each year.

For example, hot seasons with wind that happens during a very wet year help the virus spread and lead to more infections (Weaver and Kolivras, 2018).  Another factor that favors infection is contact with soil; for example, in those jobs that involve its handlings, such as agriculture, mining, and construction, which are very active in our region.

Is there anything we can do to prevent it?

Education is the key to prevention. First of all, it is necessary to remember that the arthroconidia of the fungus travel in the environment; it is their natural way of dispersion, so some reasonable measures to avoid infection are to protect oneself from contact with dust and to avoid breathing it, as in the case of sandstorms, which are frequent in our region.

Some protective measures that have been proposed are the use of masks and mouth masks for personnel who handle soil in their work or who are exposed to the environment in the field. Lastly, one of the things that have been shown to work in the past is making the general public and the medical community more aware of the disease.

One of the biggest problems with the disease is that it is easily confused with other respiratory ailments, so other similar conditions are often suspected first. A society that knows about this disease can find it faster, go to the doctor less often, and avoid complications.

Full Citation: Prensa y Colaboradores, Oficina de. “De Hongos Y Salud Pública - Centro De Investigación En Alimentación Y Desarrollo (CIAD).” Centro De Investigación En Alimentación Y Desarrollo (CIAD), 10 Feb. 2023, www.ciad.mx/de-hongos-y-salud-publica.