'Killer' Fungus Not So Deadly

FRIDAY April 30, 2010 -- The new "killer" fungus spreading through the Pacific Northwest is part reality but also part hype, experts say.

"It's definitely real in that we've been seeing this [fungus in North America] since 1999 and it's causing a lot more meningitis than you would expect in the general population, but this is still a rare disease," said Christina Hull, an assistant professor of medical microbiology and immunology and of biomolecular chemistry at the University of Wisconsin School of Medicine and Public Health in Madison.

Cryptococcus gattii, historically a resident of more tropical climates, was first discovered in North America on Vancouver Island, British Columbia, in 1999 and has since made its way to Washington state and now, more recently, to Oregon.

"It's a strain that appears to have come from Australia at some point and has adapted to living somewhere cooler than usual," Hull said.

From the point of view of sheer numbers, the new C. gattii hardly seems alarming. It infected 218 people on Vancouver Island, killing close to 9 percent of those infected. In the United States, the death rate has been higher but, again, few people have been infected.

"At its peak, we were seeing about 36 cases per million per year, so that is a very small number," Hull said.

Michael Horseman, an associate professor of pharmacy practice at Texas A&M Health Science Center Irma Lerma Rangel College of Pharmacy in Kingsville, puts the overall death rate in the "upper single digits to the lower teens. . . It's not quite what I've been reading in the newspapers."

Experts had been concerned because the new fungus seems to have some striking characteristics, different from those seen in other locales.

For one thing, the North American C. gattii seemed to be attacking otherwise healthy people, not those with compromised immune systems, as was the case in the past.

But closer inspection reveals that not all healthy individuals are vulnerable.

"I don't think everybody's susceptible," Horseman said. "Most of the people that have had the disease tend to be older males and they're not necessarily the healthiest guys in the world. A lot of them had liver disease, kidney disease, lung disease. They were probably smokers."

And many may have been taking steroids, which would put them at additional risk, Horseman added.

Infection usually starts in the lung resulting in respiratory symptoms such as coughing and, in up to 20 percent of cases, progresses to meningitis, or inflammation of the membranes lining the brain.

"If you're essentially younger and you're fairly healthy, your risk is pretty low," Horseman said. "The risk is also pretty low if you stay in urban areas and aren't digging around in the dirt or hanging around trees for long periods of time." The fungus is found in both trees and soil.

The good news is that infection is usually treatable with antifungal agents. "The treatments are pretty effective for most people," Hull said.

"This is something to keep an eye on but in terms of global things to be afraid of, this isn't one of them," she added. "If I lived in or traveled to the Northwest and developed severe respiratory symptoms that didn't resolve over time, I'd probably check that out."

"I'm going to Vancouver in the fall and, at this point, I'm not too concerned about it," Horseman added.

More information

The Oregon Department of Human Services has more on C. gattii.

Posted: April 2010


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