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April 23, 2010 -- A potentially deadly airborne fungus, widely dubbed the killer fungus, has infected more than 50 people in the U.S., according to the CDC, and is expected to spread from the Pacific Northwest where it first surfaced.
Even so, public health officials say, there is cause only for concern and awareness, but not for alarm.
The killer fungus, which first surfaced in Canada in 1999, appeared in the U.S. in Washington in early 2006. Since then, reports of cases have occurred in Oregon and Northern California.
"We wouldn't recommend that people change their habits in any way," Julie Harris, PhD, MPH, a staff epidemiologist with the CDC, tells WebMD. "We wouldn't recommend people stay indoors or don't go hiking or don't go outdoors."
The fungus species triggering the infection is Cryptococcus gattii, which can cause pneumonia or meningitis. But the infection ''simply is not common enough for people to warrant changing behavior," Harris says. "It's still very rare. People should be concerned but not alarmed."
At a news briefing Friday, Katrina Hedberg, MD, MPH, interim state epidemiologist for the Oregon Department of Health Services Public Health Division, told reporters that it's also rare that people exposed to the fungus end up getting sick.
While the CDC wouldn't specify the number of deaths, citing incomplete data, Hedberg says that ''of the 50-plus cases, around 10 of them have died."
Twelve of those 50 cases, including three deaths, have been in the state of Washington, according to Nicola Marsden-Haug, MPH, an epidemiologist with the Washington State Department of Health, Shoreline.
Marcia Goldoft, MD, a medical epidemiologist with the department, urges people to keep the threat in perspective. "The benefits of outdoor activity and exercise far outweigh the risks of a rare disease such as C. gattii."
Researchers in the U.S. have been studying the fungus, traditionally located in tropical locations, for several years, says Joseph Heitman, MD, PhD, chair of the department of molecular genetics and microbiology at the Duke University Medical Center in Durham, N.C.
The fungus, he tells WebMD, ''originates in soil and is associated with certain tree species, and becomes airborne."
While the fungus was typically seen in tropical areas of South America and other tropical and subtropical regions, it surfaced in Vancouver Island, Canada, in 1999, says Heitman, the senior author on a report on the fungus published online this week in the journal PLoS Pathogens.
"It is a microbial pathogen that can cause significant illness and even death, but it is very uncommon," he says.
Infections can be treated with antifungal agents, but no vaccine is available for C. gattii, Heitman says.
The first recorded U.S. case was in Orcas Island, Wash., Heitman says. That was followed by cases in Washington and Oregon.
Hedberg says the 50 reported cases have occurred in Washington, Oregon, and Northern California.
Heitman's team has discovered a new pathogenic strain of the fungus in the Oregon cases.
Unlike another fungus type, Cryptococcus neoformans, which typically infects those who are HIV-positive or other immunocompromised people, the C. gattii fungus can infect apparently healthy people.
The 50 cases reported to the CDC, Harris says, include people from age 15 to 95.