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W. Nile virus misses Oregon

But health officials say look for the mosquito-borne bug this spring

Oregon seems to have dodged the West Nile virus for now, but the reprieve almost certainly will end when spring's warm weather resurrects mosquito populations.

The probability is almost 100 percent, said Gary Stevens, Jackson County's director of environmental health, during a presentation to the Jackson County commissioners Wednesday.

Oregon is one of just five of the contiguous 48 states where the virus has not been detected. (The others are Idaho, Nevada, Utah and Arizona.) Stevens said it's possible the virus already has made its way to Oregon but hasn't been uncovered by any of the monitoring programs across the state.

Maybe we just didn't see it, he said.

West Nile is a viral infection first isolated in 1937 in Uganda. The virus reproduces in infected birds and travels from bird to bird by mosquitoes, which spread the infection when they bite to drink blood. Mammals, including people, aren't usually part of the cycle but can get infected if bitten by a mosquito carrying the virus.

Stevens told the commissioners that the experience of states where the virus already has surfaced gives Oregon public health officials a good sense of what to expect next summer. Most people who get the virus will never know they have it.

Only one in five people who have been infected will show symptoms, which typically include aches and pains, a low fever, swollen lymph nodes, loss of appetite and nausea. Fewer than — percent of patients who are diagnosed with the virus will develop potentially fatal neurological problems, including seizures and polio-like paralysis that can be fatal.

Stevens noted that the virus strikes horses harder than humans: It's fatal in 30 to 40 percent of equine cases, but only about 5 percent of human cases are serious enough to be reported. There is no human vaccine or drug that targets West Nile, and care is limited to treating symptoms. An equine vaccine has been licensed, but its efficacy has not been determined.

The virus was first found in the United States in 1999, when a few East Coast residents were infected. This summer the virus spread, with human infections reported in 38 states and the District of Columbia. As of Tuesday, the national Centers for Disease Control and Prevention had logged 3,399 cases of West Nile infection this year, 193 of them fatal.

The virus also had been identified in about 6,400 horses, thousands of birds (mostly crows, jays and ravens), dogs and a few small mammals, including a chipmunk, a skunk, a squirrel and a domestic rabbit.

Stevens had some good news about the virus in the face of its eventual arrival: He noted that it is spread only by mosquitoes ' not between humans or from horses to humans ' and less than — percent of mosquitoes seem to carry it.

What we need to do is prevent mosquito breeding, he said, noting that mosquitoes can breed in standing water that collects in old tires, abandoned swimming pools or stock troughs.

Stevens said public health officials across Oregon will spend the winter educating people about the virus and encouraging them to use insect repellent to reduce the likelihood of their exposure. He said Jackson County's Web page will have information about the virus within two weeks ().

Information about the virus also can be found on the Web site maintained by the CDC ().

Reach reporter Bill Kettler at 776-4492, or e-mail

The Associated Press contributed to this story.