热带真菌已入侵太平洋西北部

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A rare and dangerous fungus has been spreading in British Columbia and the U.S. Pacific Northwest. It causes serious lung and brain infections. It can be fatal. Now, researchers have discovered that a unique strain of the bug has emerged in Oregon. Officials are not calling this a public health emergency, but they are telling doctors to watch for cases. NPR's Richard Knox reports.

RICHARD KNOX: Until a decade or so ago, infections of this fungus, called Cryptococcus gattii, were never seen outside really warm places, such as Australia, Papua New Guinea, tropical South America and Egypt.

Dr. JULIE HARRIS (Centers for Disease Control and Prevention): So it was really surprising, in 1999, to find that in this temperate climate of Vancouver Island, people were getting sick with Cryptococcus gattii.

KNOX: That's Dr. Julie Harris. She's a specialist in fungal diseases at the Centers for Disease Control and Prevention. Harris says U.S. doctors started reporting cases of this strange disease six years ago.

Dr. HARRIS: Starting with, you know, just one to two cases per year in 2004 and 2005, to now, when we get dozens of cases per year.

KNOX: So far, there've been about 220 cases reported in British Columbia, and about 50 in Washington and Oregon. Around 40 people have died from infections that overwhelm the lungs and the brain.

Now, fortunately, fungal diseases like this are generally not passed from person to person. People get them from the environment. But researchers don't know why people and animals in the Pacific Northwest are getting infected with this tropical fungus, and why only a few who get exposed, get sick.

Dr. HARRIS: This is an airborne infection, and so these spores are really, really small and they can be carried in the air. And so, you know, hypothetically, anyone can inhale them.

KNOX: The fungus likes to hang out in forests, on trees in the surrounding soil. Many of those whove gotten sick so far have worked in jobs like forestry or construction. But many others have had only casual exposure to the woods or none at all.

Dr. HARRIS: You know, while we certainly can't say that this pathogen is everywhere, it's really challenging to say where it's not.

KNOX: Researchers have been struck by the number of different animal species getting infected: domestic cats and dogs, sheep and horses, elk and llamas, even porpoises and dolphins. This fungus is popping up in lots of different places. It's also changing.

Edmond Byrnes and his colleagues at Duke University Medical Center have discovered a new strain of the fungus unique to Oregon.

Mr. EDMOND BYRNES (Graduate Student, Duke University Medical Center): The new strain has only been around for a few years, and has already spread throughout much of Oregon. So I think it's clear that the organism is likely to spread further into Northern California.

KNOX: Their report is in the journal, PloS Pathogens.

Many experts think the spread of Cryptococcus gattii is a symptom of climate change. One thing is certain: these tiny spores can cause devastating illness. Bob Lewis of Portland knows about that. He was a hearty outdoors type when he got infected.

Mr. BOB LEWIS: In the spring of 2007, I felt I had something wrong with my chest and I went to the doctor. And they took X-rays and thought it was bronchitis.

KNOX: Months passed, the undiagnosed infection got worse. Thats typical, doctors often don't know what to look for and the fungus can hide in the body for months before causing serious illness. There's no quick test for it.

Finally, Lewis ended up in the hospital. Specialists were surprised to find he had one of the first Oregon cases of Cryptococcus gattii. The disease was certainly news to him.

Mr. LEWIS: Never heard of it. In fact, I couldn't even say the name of it for a week or so.

KNOX: Then Lewis's lung infection started growing fast. His wife, Joan, says he was gasping for breath.

Ms. JOAN LEWIS: At that point, our primary-care physician took me aside and said, Joan, if we can't get him breathing better on his own, he cannot survive more than three days. And, of course, that was a tremendous shock.

KNOX: Doctors eventually found expensive antibiotics that killed the fungus. But ever since, Bob Lewis has had to trail an oxygen tank and his health has never been the same.

Mr. LEWIS: My heart couldn't do the job it needed to do, so my left ventricle got enlarged. And then my kidneys developed a critical level of dysfunction. But I'm one of the lucky ones.

KNOX: The Lewis's weren't aware, until this week, that 39 cases of the disease have been reported in Oregon.

Mrs. LEWIS: Makes me want to cry, to hear those kind of numbers. This is a tragic and very, very frightening experience, and I wouldn't wish it on anybody.

CDC officials say there's really nothing people can do to minimize their risk. But they want physicians to be alert so patients don't have to wait as long as Bob Lewis did for diagnosis and treatment.

Richard Knox, NPR News.

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