A newly discovered strain of airborne fungus that has caused several deaths in Oregon seems set to spread, researchers say.

The microscopic fungus, called Cryptococcus gattii, lives on trees and in soil, and releases spores that can lodge in the throat, causing an infection. The infection can be treated with antifungal medication, but there is no vaccine to prevent or any precautions to take to avoid it, the BC Centre for Disease Control's website said.

Symptoms can appear two to several months after exposure, and may include a cough lasting weeks, sharp chest pain, shortness of breath, meningitis-related headache, fever, nighttime sweats and weight loss.

The mortality rate for recent C. gattii cases in the Pacific Northwest is running at about 25 per cent or six deaths out of 21 known cases analyzed in the United States, compared with a mortality rate of 8.7 per cent or 19 out of 218 known cases in British Columbia, researchers reported in Thursday's issue of the journal PLoS Pathogens.

"This novel fungus is worrisome, because it appears to be a threat to otherwise healthy people," said Edmond Byrnes III, a graduate student in molecular genetics and microbiology at Duke University in Durham, N.C.

"Typically, we see this fungal disease associated with transplant recipients and HIV-infected patients, but that is not what we are seeing," he added in a release.

The new strain seems poised to move into California and other adjacent areas, the researchers said.

There can be more complications in people infected with it compared with a more common and related fungus, Cryptococcus neoformans.

Severe infections

Because the new version or genotype of C. gattii, known as VGIIc, hits some humans and animals so severely, the researchers called for greater awareness and vigilance.

Doctors need to know if they are dealing with a virulent or harmless strain, which involves growing or culturing the fungus and then sequencing its DNA.

The new type reproduces both sexually and asexually, so researchers are trying to determine its origin by closely studying the genetics of samples.

The organism has also attacked domestic and wild animals, the study's authors said.

The research team also included scientists from the United Kingdom, New York, Sydney, Australia and Oregon.

This work was funded by the U.S. National Institutes of Health and U.S. National Institute of Allergy and Infectious Diseases.