West Nile virus crews fanned out across Lancaster city Wednesday to drop blocks of a mosquito-killing insecticide into storm grates, the first wave of prevention in what is feared to be a banner year for the sometimes deadly virus.

"I've confirmed the fact that there are much more mosquitoes this year than last year at this point," warns Matt Mercer, Lancaster County coordinator for the state-run West Nile Virus Mosquito Control Program.

"This year with the amount of water around and then this heat, that seems to play into triggering the West Nile virus activity."

Kim Wissler, a city health officer, has fielded 15 complaints in the last two weeks from people calling to report standing water in containers, tires, rain barrels, flower pots and on construction sites.

"There's so much activity. It's like, bam, it happened so very quickly," Wissler said, noting that in each case, the landowner, landlord or tenant removed the problem promptly.

Lancaster County had the dubious distinction of being one of the most active counties with West Nile virus in the state in 2010.

Six residents were hospitalized with the virus, but none of the cases was fatal. It was the most human cases here since 37 in 2003. Only Philadelphia, with 13 human cases, had more in 2010.

Statewide, there were 28 human cases — none fatal — the most since 2003.

Lancaster County also had the third-most samples of mosquitoes carrying West Nile virus (108), a tie with Erie County for the most dead birds found killed by the virus (six) and the most animal cases (a llama and three horses).

Within the county, Lancaster city had 46 samples of adult mosquitoes carrying the virus last year. That was, by far, the most found.

Other municipalities with the most samples of infected mosquitoes were Manheim Township with 13, Lancaster Township with 12 and East Hempfield Township with 10.

However, adult biting mosquitoes carrying West Nile virus were found in all corners of the county, including Conoy Township, Elizabethtown Borough, East Drumore Township, Ephrata Borough and Salisbury Township.

Because of the uptick in West Nile activity in Lancaster County, the state Department of Environmental Protection increased funding for Lancaster County's anti-virus program from $80,000 to $95,000 this year, which allowed Mercer to hire a second seasonal technician to help combat the mosquito population.

The virus is spread to humans, birds, horses, mules — and now a llama — by bites from infected mosquitoes, which pick up the virus by biting infected birds.

Not all mosquitoes carry the virus. There are two mosquito species here that crews are gunning for: Culex pipiens, the common house mosquito and a human biter, and Culex restuans.

Most people, when they get the virus, experience only flu-like symptoms. But the virus can prove fatal. In 2003, two of the 37 people who got the virus died.

One first line of defense began Wednesday morning as crews spread across the city to place an insecticide aimed at killing mosquito larvae into all the city's approximately 2,000 storm grates. Assisting the effort were inmates from Lancaster County Prison.

Since April, Mercer and his helpers have been placing traps around the county in search of mosquitoes that carry the virus.

In riverside pools of water near Marietta, adult mosquitoes were found earlier than they have been in the 10 years that the monitoring program has been in operation.

No mosquitoes tested so far are infected with the virus.

Crews also sample pools of standing water around the county to search for mosquito larvae, to find mosquito hotspots.

When infected adult mosquitoes are found, nighttime spraying usually follows.

"It's out there," Mercer observes. "It's in the bird community and it's just a matter of time before it surfaces."

Mercer and Wissler emphasize the best way to combat the spread of West Nile virus is for residents to make sure they don't have standing water around where mosquitoes lay eggs.

Common breeding grounds include flower vases, stopped-up rain gutters, tires, rain barrels and small ponds that are not filtered.

Tall grass and thick vegetation also increase the likelihood of mosquitoes.

West Nile virus officials also ask residents to report dead birds that appear to have recently died. Call the Penn State Cooperative Extension office at 394-6851.

acrable@lnpnews.com