West Nile virus could hit area hard this summer

As dusk falls over the wetlands that border a huge park-and-ride lot in Kenmore, the crows of one of King County's largest roosts assemble once again to put on the nightly show that ends their day.

Waves of the jet-black birds flap through the fading light, arriving home to the tall Douglas firs, cottonwoods and cedars from their day's travels. A cacophony of familiar "caw-caw" calls rises from the woods as they welcome one another. Then the hundreds of proud birds settle in for the night.

Later this summer, these crows and their cousins throughout the state could die by the thousands, scientists warn. And if they do, they will be signaling that a heavy season of potentially deadly, mosquito-borne West Nile virus is upon us.

"They're sentinels for us," says John Marzluff, a University of Washington professor of forest resources who is a nationally known crow expert. "They die, and they're very visible when they die."

No one knows whether the virus will really take hold this summer and spread across the state with hundreds of human cases. But if the experience of a few other states is any indication — and if we have a hot summer along with some rainy spells — the illness could be a significant problem.

Last year, the state finally had its first three human cases, all relatively mild, after four years of finding the virus in a few horses and birds, mostly crows. It was one of the last states in the nation to have human cases.

Typically, it takes three years or so for the human cases to take off. But in Colorado, for example, the cases skyrocketed in just one year, from 14 cases in 2002 to 2,947 in 2003. In Idaho, the cases jumped from 13 in 2005 to 996 last year — only the third year after its first case. And California went from one case in 2002 to 779 in 2004.

Help prevent West Nile virus

Reduce mosquitoes: Eliminate standing water, as in buckets, tires, cans and plant saucers. Frequently change water in bird baths and wading pools.

Protect yourself: Screen windows. Wear long sleeves and mosquito repellent outdoors.

Report dead birds: Some will be tested for West Nile virus. Call 206-205-4394 or report online at www.metrokc.gov

Source: Public Health — Seattle & King County

It's worrisome enough that local government officials announced this week that crews in Seattle, Bellevue and Kirkland will soon inject special bacteria into drainage catch basins to kill the mosquito larvae.

"You could have an intense year, even though you had a small number of cases last year. There is certainly no hard-and-fast rule," said Emily Zielinski, a behavioral scientist with the Centers for Disease Control and Prevention.

Buildings aid breeding

Warm weather, which mosquito larvae need to hatch, has been key to an increase in West Nile cases elsewhere.

Marzluff and six UW colleagues recently reported in a new study that the number of Culex pipiens mosquitoes, which can carry West Nile, increases with the temperature. The research team, which trapped the insects in the Seattle area over two summers, also found that they were most abundant in the cities and suburbs, where buildings trap heat and make breeding conditions more favorable.

Information

Centers for Disease Control and Prevention's West Nile Web site: www.cdc.gov/westnile/

And the National Weather Service says odds are a little higher than usual that the summer will be warmer than normal from July through September. Mosquitoes typically need only a week or less of weather in the high 70s or so to hatch from eggs laid in standing water.

West Nile is spread to humans when mosquitoes bite an infected bird, then bite a person. The insects are most active in early morning and at dusk and are drawn to the carbon dioxide in exhaled breath as well as sweat and body odors to collect their "blood meal." Insect repellents containing DEET are effective in keeping them away.

That's why crows and other birds play a crucial role. Culex pipiens mosquitoes normally live only a few days to two months or so. Scientists believe most bird species can survive the virus indefinitely.

Though crows usually die within two weeks of contracting the virus, in their final days they are sitting ducks for feeding mosquitoes.

"Sometimes you see roosts with clouds of mosquitoes above them," said Marzluff.

Add to that the fact that, just as in Kenmore, communal roosts with huge populations of crows are often in mosquito-friendly habitat: areas with large trees protected by wetlands or on islands.

In addition to Kenmore, other large roost areas include Foster Island in Seattle's Washington Park Arboretum and several islands in the Snohomish River.

It's not just crows that are at risk. Other local birds vulnerable to the virus include Steller's jays, chickadees, gulls, song sparrows, house sparrows, house wrens and Western bluebirds, Marzluff said. Robins also may die after carrying the virus for a while, he said.

Those are among 317 bird species nationwide that can be killed by the virus, according to the Centers for Disease Control and Prevention. But the CDC says most species can survive the infection. That makes them long-term reservoirs of the virus.

"Take it very seriously"

Health authorities are concerned that the public remains complacent about West Nile because it has taken so long to infect humans here.

Eighty percent of those infected don't even become ill, and as many as 20 percent have relatively mild, flulike symptoms. But about one in 150 develops a severe, potentially fatal illness because the virus enters the nervous system. Symptoms can include high fever, headache, neck stiffness, disorientation, coma tremors, convulsions, muscle weakness and paralysis.

In Idaho last year, 171 West Nile patients had this "neuroinvasive" illness, and 23 of them died. In all, there were 996 reported cases there last year, but many more people likely got it and never received a diagnosis or reported to health authorities, experts say.

As one of the 171, Mel Lacy knows all too well how devastating the infection can be. The 50-year-old Middleton, Idaho, electrician nearly died from West Nile last August. He is still partially paralyzed and uses a wheelchair.

"It was pretty hairy for a while," he said. "It really spiraled down quickly."

His illness started with flulike symptoms, but within six days he couldn't stop vomiting and was hospitalized. Soon he was on a ventilator and couldn't move anything but his head and neck.

After months in the hospital, he started a difficult rehab in other hospitals that was interrupted by respiratory failure twice and heart failure once. Finally, the day after Christmas, Lacy was able to go home, where he has continued physical therapy.

Now Lacy can use his hands and feed himself again, but he can't hold his arms out for long. Still, he is working on walking again, and he says he is sure he will someday be able to use all his muscles.

Lacey lived around mosquitoes all his life, and it never made him sick. In fact, he hadn't really heard much about West Nile in humans before he became a victim.

"Take it very seriously," he advises now.

"It can totally change your life."

Warren King: 206-464-2247

or wking@seattletimes.com