Human fungal outbreaks traced to Brazil rainforest

Over the past two decades, a deadly fungus previously only found in tropical and subtropical climates has begun infecting humans in other climate zones. So how has this fungus increased its reach?

In 1999, a highly infectious fungus called Cryptococcus gattii emerged on Vancouver Island in Canada. By 2007, the strain had killed 19 people and sickened more than 300 humans and animals on the island. The fungus has since spread into the United States with dozens of cases reported in California, Idaho, Oregon, and Washington. But where had this infectious fungus come from?

Before the Vancouver Island outbreak, C. gattii didn’t exactly fit the typical profile of a fatal infectious disease for the region. It was known to cause infections in humans and animals but never at the high rate that was reported on Vancouver Island. And previously, those infections were in tropical or subtropical climates where the fungus typically resides in tree hollows. Scientists have been puzzled by where the strain had come from and how it adapted to the cold so well.

Now, a new study by a group of international researchers might have answers to both of those questions. In a paper published in the journal PLoS ONE last week, the team reported that this strain of C. gattii originated in the rainforest of Northern Brazil where the genetic diversity of the pathogen is relatively high. In addition, they believe that global warming trends might be playing a role in the fungus’s spread as well.

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