Coming this summer to a water drain near you: a crew with a motorized tank full of mosquito-larva-killing bacteria and a specialized gun...

Coming this summer to a water drain near you: a crew with a motorized tank full of mosquito-larva-killing bacteria and a specialized gun that releases small amounts of the agent with every shot.

The target: West Nile virus.

Seattle officials Monday announced that this 14-person crew will hit most of the city’s 46,000 street water drains as the city gears up to fight what they worry could be an increase in cases of the disease.

Bellevue and Kirkland also will receive the preventive doses.

Only three people in Washington got West Nile virus last year, one of the last states in the nation to be affected. But health officials say they expect an increase because once the virus is present, chances of it spreading increase.

“The potential is definitely there,” said Sharon Hopkins, a veterinarian for Public Health — Seattle & King County, as she joined other officials Monday on Queen Anne Hill to demonstrate the larvacidal technology.

Hopkins said the virus follows a certain pattern: For the first few years, it appears in birds and horses. Then a couple of cases appear in humans, followed by a few more human cases the next year. Then it tends to expand exponentially. In Idaho, for example, cases went from the single digits to more than 1,000 over less than four years.

So in hope of preventing that from happening here, the crews will fan out across the city to disperse the larvicide — little corn-based granules full of bacteria — into the water drains, a place where mosquitoes are known to breed.

When mosquito larvae eat the bacteria, the bacteria release toxins that cause the larvae to stop eating and starve.

City officials said they did two years of research and concluded that the method will have minimal impact on the environment.

The bacteria are harmless to other organisms, and will eliminate the need to use other sprays to kill mature mosquitoes, said Sheila Strehle, the city’s West Nile response coordinator.

In 2006, three people in the state were confirmed with West Nile; none died. One horse and six birds have died from the virus in King County, according to the state Department of Health.

No cases — in humans or animals — have been reported this year.

But mosquito season really starts in July, when mosquito larvae begin to hatch. It hits its peak in August.

So the officials urged residents to use bug repellent, eliminate standing water in yards, and clean any clogged rain gutters, another often-overlooked place where mosquito larvae hatch.

Earlier this year, the state Department of Health also launched an advertisement campaign to educate people about the virus.

“It’s time for people to take it seriously,” said Tim Church, a spokesman for the department. “We’re more concerned than ever because of what has happened in our neighboring states.”

Manuel Valdes: mvaldes@seattletimes.com or 206-748-5874