Rare airborne fungus usually found in tropics has taken root in Pacific Northwest and has sickened 60 people and killed 15 in the past several years, health officials said Thursday.

The fungus, Cryptococcus gattii, can cause life-threatening respiratory illnesses if its spores are breathed in by people or animals, according to a weekly report published by the U.S. Centers for Disease Control and Prevention (CDC).

The fungus, found on and around trees, is not contagious among people. C. gattii infection causes a prolonged cough, shortness of breath, headache, fever, weight loss, and, in some patients, a stiff neck. Symptoms can take months to develop after exposure, from six to seven months.

The overall risk to the public is very low, and people do not need to avoid going outdoors and exercising, said Julie Harris, an epidemiologist with the CDC.

The first human infection reported was in Oregon in December 2004 with 60 cases -- 43 in Oregon, 15 in Washington, one in California and one in Idaho.

Of the 15 deaths, nine of the patients who were infected (20 percent) died due to their infection, and six others died of other reasons while infected with the fungus. The CDC reported that most of those who got sick had another condition that likely made them more susceptible to the fungal illness.

The CDC is also aware of 52 cases in animals, including cats, dogs, ferrets, elk and porpoises.

"It can be fatal to animals. Animals are closer to the ground, they're sniffing around, so we think they are probably more susceptible to infection than humans," Harris said.

The type of C. gatti found in the US is uncommon in other parts of the world. According to Harris, C. gatti is unlikely to spread because "fungi need very special environmental conditions to survive and to propagate."