Image courtesy Edmond Byrnes and Joseph Heitman, Duke Dept. of Molecular Genetics and Microbiology
Updated May 2, 2010
A new strain of hypervirulent, deadly Cryptococcus gattii fungus has been discovered in the United States, a new study says.
The outbreak has already killed six people in Oregon, and it will likely creep into northern California and possibly farther, experts say.
The new strain is of the species Cryptococcus gattii, an airborne fungus native to tropical and subtropical regions, including Papua New Guinea, Australia, and parts of South America. An older strain of the fungus was frst detected in North America in British Columbia, Canada, in 1999.
No one knows how the species got to North America or how the fungus can thrive in a temperate region, experts say.
"The alarming thing is that it's occurring in this region, it's affecting healthy people, and geographically it's been expanding," said study co-author Edmond Byrnes, a graduate student at the Joseph Heitman Lab at Duke University.
Less common than bacterial and viral infections, fungal diseases usually strike people with weakened immune systems—part of what makes the recent deaths of otherwise healthy people in Oregon so worrisome.
People can become infected with Cryptococcus gattii by inhaling the microscopic organisms—and there's not much you can do about it.
There's no vaccination or other preventative measure available for the new strain, though the infection can be treated with antifungals, the study says. And "there are no particular precautions that can be taken to avoid Cryptococcosis," according to the British Columbia Centre for Disease Control. "You can, however, be alert for long lasting or severe symptoms and consult a physician (or veterinarian for animals) for early diagnosis and treatment."
Appearing several months after exposure to the fungus, the infection causes a bad cough and shortness of breath, among other symptoms.
On a positive note, fungal infections, unlike viruses, can't be passed from person to person.
(See pictures of a new species of glowing fungi.)
Fast-Spreading Cryptococcus Gattii Superfungi
The first U.S. Cryptococcus gattii cases were identified in 2005. It wasn't until the new study, though, that genetic analysis revealed that the fungus is a new strain that had originated in Oregon.
Of the 21 known cases involving the new strain, 6 have been fatal—about 25 percent. The new strain has so far been deadlier than the strain in British Columbia, which killed 19 out of 218 known victims, or 8.7 percent.
The organism has also attacked domestic and wild animals, according to the study, published April 22 in the journal PLoS Pathogens.
Though the reason for the new strain's severity is unknown, "one thing fungi do that bacteria don't is they have sex with each other," Byrnes noted. (Related: "Rainmaking Bacteria Ride Clouds to 'Colonize' Earth?")
As with humans, nearly every fungus offspring represents a new combination of genes and their resulting traits. So it's possible that the new fast-spreading superfungi is the result of Cryptococcus gattii mating. (Learn more about human diseases.)
No matter how it arose, the tropical interloper looks like "it's going to stick around," Byrnes said, "at least for the foreseeable future."
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