West Nile Virus Found in Hawaii

A wild sparrow captured at Kahului Airport on Maui has tested positive for West Nile virus, the first indication that the mosquito-borne disease has made it to Hawaii.

If the initial test results prove accurate, then Hawaii's birds, "already suffering from avian malaria and avian poxvirus, will face the onslaught of West Nile virus," said David Duffy, a professor of ecology at the University of Hawaii, writing on a scientific listserv that tracks the disease.

West Nile infects birds, humans and other animals and is transmitted by mosquitoes. It made its U.S. debut in 1999 in the Bronx, and has made its way farther West each year. Only Hawaii and Alaska had remained untouched as of late this summer.

No one knows for certain how infected mosquitoes made it across the Pacific, but scientists had previously predicted that some would manage to hitchhike in airplanes. In a recently published article in the journal EcoHealth, scientists affiliated with the Consortium for Conservation Medicine in Palisades, N.Y., estimated that seven to 70 West Nile-infected mosquitoes would reach Hawaii by plane each year once the disease became established on the West Coast, as it did this year.

About 82 percent of those would travel in the cargo hold, they predicted. The rest would enjoy the comforts of coach, business or first class.

With so much air traffic funneling through Honolulu's busy airport on Oahu, aggressive mosquito control efforts had been focused there. Spraying is to begin on Maui, as well, the Honolulu Star-Bulletin reported.

As of this past Tuesday, there were 1,784 U.S. cases of West Nile in humans (including one in the District, three in Virginia and 11 in Maryland) and 56 deaths, none in the D.C. region.

-- Rick Weiss

Visual Cortex Altered in Blind

A part of the brain that normally processes visual stimuli is transformed into a language center in blind people, new research shows.

The study offers convincing evidence of the "plasticity" of the brain -- the term neuroscientists use to describe the ability of the brain to acquire new functions.

Previous research had hinted that the visual cortex in blind people was being used when their verbal skills were tested. The new research showed that during transient disruptions of the visual cortex, blind people had difficulty performing verbal tasks.

Scientists had a group of nine blind people listen to a series of nouns and asked them to produce a matching verb in response. For example, the word "apple" was designed to elicit the verb "eat."

Researchers induced transient problems in the visual cortex of the blind volunteers using a technique known as transcranial magnetic stimulation. "They actually made more mistakes," said Agnes Floel, a research fellow at the National Institute of Neurological Disorders and Stroke, and one of the authors of the study. "The error rate went up, but they were also slower."

A group of volunteers with normal sight was given the same test. Disrupting the visual cortex among these people did not increase verbal errors.

Researchers said all the blind people had been blind from birth or from a very young age, and it was unclear whether people who went blind at older ages would experience the same phenomenon.

"It tells you about the possibilities of plasticity in the brain," Floel said in an interview. The study was published yesterday in Nature Neuroscience.

-- Shankar Vedantam

Duo Identifies Ultra-Low Hum

Scientists think they have found the source of a mysterious hum that reverberates through Earth, too low for human ears to hear.

They used to think it came from earthquakes; a big quake will set the whole planet ringing like a bell. But even when there are no big quakes, the hum continues, a slow, steady slosh of waves around the planet.

Now, with instruments in California and Japan, scientists have pinpointed the source. The hum, they say, starts in the oceans, when winter storms whip the waves into a frenzy.

"These waves interact with each other to create longer waves that reach deep into the ocean, all the way to the ocean floor," said Barbara Romanowicz, a seismologist at the University of California at Berkeley.

It is the thumping of those waves on the bottom, like the pounding of a drum, that sets Earth vibrating in a phenomenon known as free oscillation, she said. She and graduate student Junkee Rhie put forth their explanation in Thursday's issue of the journal Nature.

The hum has fascinated scientists since its discovery six years ago by a group in Japan.

It consists of long, slow seismic waves that raise the ground by a fraction of an inch as they go by. It takes five minutes for two of these waves to pass a given point. They put out very little power, about as much as a couple of 100-watt light bulbs, Romanowicz said.

Although these waves crisscross the planet all the time, people cannot feel or hear them. In musical terms, the sound would be about 16 octaves below middle C.

-- Knight Ridder Tribune

West Nile virus, transmitted by mosquitoes, infects humans and animals.