Most patients infected with the rare Cryptococcus gattii fungus develop serious brain and lung infections, like the one shown in this X-ray.
A rare fungus found in soil and trees has sickened hundreds of people in British Columbia and the Pacific Northwest in the last decade -- and killed dozens -- but scientists now say they’re seeing different strains of the potentially deadly bug in additional U.S. states.
As of June, 171 cases of infection caused by Cryptococcus gatti, a fungus once confined to tropical climates, had been reported in the U.S. That includes at least 100 cases in Oregon and Washington, where officials have been tracking an outbreak since 2004.
But at least 25 cases have been detected in eight states outside of the Northwest since 2009 -- and six of those patients died, according to a new report in the journal Emerging Infectious Diseases.
No one’s calling it a public health crisis; officials at the Centers for Disease Control and Prevention say they just want to raise awareness.
“It is really, really rare; very few people get infected by this,” said Dr. Julie Harris, a fungal disease expert with the CDC. “You can still go outside, you can still do your daily activities.”
Of the six patients in the new tally who died, four succumbed to severe lung and brain infections before they were diagnosed. A previously healthy 18-year-old Georgia woman showed up at a community hospital with a headache and fever -- and died within two weeks of getting sick.
Of those who provided travel information, none had been to the Pacific Northwest recently, the study found.
Thirteen of the newest U.S. cases were reported in California, with five more in Georgia, two in New Mexico and one each in Alabama, Florida, Hawaii, Michigan and Montana.
The original outbreak was caused by three specific strains of C. gattii, but the new cases, including those in nearby California, were caused by unrelated strains, Harris said.
People are typically infected when they inhale the airborne spores of the fungus that began causing disease and deaths in 1999 in Canada. Since then, 338 cases have been tracked in British Columbia, health officials told NBC News. As of 2010, about 40 people in the U.S. and Canada had died from C. gattii infections, according to latest figures.
The reason the new cases are interesting, and worth documenting, is because they provide evidence that C. gattii isn’t confined to the Northwest and could be an unrecognized source of pneumonia and meningitis across the U.S.
“I think it’s something that has been going on and we haven’t found it because we haven’t looked for it,” said Harris.
Most Cryptococcus infections in the U.S. occur in people with weakened immune systems, such those with HIV or those who’ve recently undergone organ transplants. In many cases, they get C. neoformans, a close cousin to C. gattii, and much more readily recognized. Patients are typically treated with strong anti-fungal medications.
In the newly documented cases, doctors who encountered patients with puzzling fungal infections took their diagnoses a step further and insisted on testing for C. gattii. Because the infections aren't required to be reported outside the Northwest, such sporadic testing provides the only data that scientists have that the fungus is present in an area, Harris said.
Before 1999, C. gatti was mostly found in the tropical and subtropical regions of the world. But that year, it showed up on Vancouver Island, British Columbia, where it began infecting people and animals. By 2004, it was making people sick in Oregon and Washington and by 2011 it had become a reportable disease in those states.
Scientists don't know why it took hold in the Northwest, though they speculate that climate change may have contributed and that the fungus was then spread by commerce or travel.
C. gattii is alarming because it can strike healthy people and because it has a long incubation period -- from a few days to several months in some cases. Although many people are exposed to it, doctors don’t know why only some are sickened by it.
There’s not really anything hikers and other outdoor-lovers can do to reduce their risk of contracting a C. gatti infection, Harris said. The new information is more of a warning for doctors and health workers to consider the bug when they’re stumped by a puzzling infection.
“We just want them to know that, hey, these infections are not limited to the Pacific Northwest, or to people who travel there,” Harris said.
JoNel Aleccia is a senior health writer with NBC News. Reach her on Twitter at @JoNel_Aleccia or send her an email.
First published September 11 2013, 9:21 AM