A potentially lethal fungus is showing up in Oregon in a rare but highly virulent form. The fungus appears to be genetically distinct from similar strains that have been cropping up around the Pacific Northwest for more than a decade.
Cryptococcus gattii has been slowly spreading since at least 1999 across the Pacific Northwest, where it has caused more than 200 severe brain and lung infections and killed 24 people.
But a newly described strain called VGIIc is especially concerning, researchers report online April 22 in PLoS Pathogens. The strain is responsible for three of the seven known human cases of C. gattii infections in Oregon, says microbiologist Edmond J. Byrnes III of Duke University Medical Center in Durham, N.C.
“We don’t want to overly alarm people, because it’s still actually a very rare infection,” says environmental hygienist Karen Bartlett of the University of British Columbia in Vancouver, Canada, who was not part of the team that identified the new strain. But because this is the tropical pathogen’s first incursion into the temperate zone, she warns, “Physicians could potentially miss the diagnosis.”
The fungus has been known for years in warmer places such as South America, Southeast Asia and Australia. In the Pacific Northwest, the fungus thrives in an unusual range of places, says Joseph Heitman, a physician and microbiologist at Duke who collaborated on the study. It lives in soil and grows harmlessly on tree bark, particularly Douglas firs. People catch infections by inhaling spores or fungal cells wafting around in the environment and may not show symptoms for months after being exposed. Those who prove susceptible — for reasons not yet clear — can suffer prolonged coughs, weight loss and the general feeling “of being hit by a truck,” Bartlett says.
C. gattii could keep spreading in the Northwest, probably down the coast, Bartlett says, because cold winters with prolonged freezing of the soil are expected to limit its creep eastward.