This Poison Fungus Is Evolving to Get Deadlier

It's not just bacteria: A fungus in the Pacific-Northwest is adapting into a more resilient version of its ancestors.

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Jul 16 2014, 10:30am
Cryptococcus gattii. Image:Wikimedia Commons/​Djspring

Fungus in the Pacific-Northwest is a highly peculiar thing. An overnight rain when the temperature is just right will yield a forest full of alien not-plants sprouting from soil, decaying matter, and healthy, living trees—all in a matter of hours. These aliens, found in colors and shapes that could really only be of extraterrestrial origin, sprout mushrooms, and some of those we might eat. So many of the rest, however, are often just grotesque, at least to a certain eye accustomed to the usual green order of a forest.   

Some of these fungi are poisonous to humans, of course, but by and large fungi are considered our friends. Disease-wise, we usually worry about bacteria and viruses, despite the latent virulent potential of many of the fungi we co-exist with. Virulence is really what we should expect from a class of life capable of such rapid growth. Human immune systems, however, are very good at keeping it in check, and fungal infections are often seen as signs of immune system weakness, becoming highly destructive in the presence of HIV/AIDS in particular. But a stroll through that damp Oregon forest is a good enough reminder of that potential to do a great deal of harm in virtually no time.

The Pacific-Northwest now finds itself home to a fungal species known as Cryptococcus gattii, a Brazilian variety first discovered on Vancouver Island in 1999. Fifteen years and several deaths later, C. gattii has adapted to its new home and now poses a threat serious enough to warrant “global health vigilance,” according to a new open-access study from the Translational Genomics Research Institute (TGen). "We identified several genes that may make the outbreak strains more capable of surviving colder environments and that make it more harmful in the lungs," said David Engelthaler, the study’s lead author, in a TGen statement.

The study, according to its authors, is among the largest investigations into a single fungus strain ever conducted. With support from the CDC, it encompassed 24 researchers from 13 institutions in seven nations. Together they sequenced 115 genomes of C. gattii collected from 15 different countries. The results for the Pac-NW strain are rather chilling, but also point the way to new treatments and diagnostic tools.

By 2010, the fungus had infected at least 60 people in the Pacific-Northwest, according to the CDC. Of the 45 patients with known outcomes, 15 died. A mortality rate of over 30 percent is no joke. As a tropical phenomenon, the fungus has been known to attack nervous systems, but the latest version appears to have acquired a new ability to cause severe (and deadly) lung infections in addition.

The newly adapted fungi has moved fast, spreading quickly through the rest of the Pac-NW region and on down through Oregon. The TGen sequencing is as much an insight into how to handle the fungus now as it is to handle what it might become. Fifteen years on, it’s become a uniquely adapted, uniquely dangerous version of its Brazilian kin. There’s every reason to think that, as it continues to adapt to its new Pac-NW home, C. gattii will get more and not less dangerous: a creepy addition to a public health landscape becoming more and more defined by adaptation to adaptation.