YAPHANK, N.Y. (CBSNewYork) — A West Nile warning has been issued on Long Island.

A large number of mosquitoes are testing positive for the virus, including more than two dozen samples in one week alone in Suffolk County.

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Dr. Scott Campbell and his team at the Suffolk County Health Department sort and identify mosquitoes at their lab here after trapping thousands at some 50 sites. The samples have been sent for testing in Albany and results from the second week of August showed a scary spike — 29 mosquitoes testing positive for West Nile virus. All were female culex mosquitoes, according to the Health Department.

“They are temperature dependent, so the hotter the environment, the faster the mosquitoes develop,” Dr. Campbell said.

Temperatures went into the 90s that week. Mix that in with recent rain and experts say it creates a breeding frenzy and a higher likelihood of picking up West Nile, which can cause a fever, encephalitis or meningitis.

Suffolk County residents said they are concerned.

“When we go out to walk the dog in the evening there’s so many mosquitoes out, even when you put spray on it doesn’t help,” said Kathy Clark of Moriches.

“I don’t really feel it. I notice it after,” 7-year-old Celia Welch added.

Siblings from England told CBS2’s Rozner they’ve been staying in the United States all summer, but didn’t get bit until visiting Huntington on Monday.

“I’ve noticed I’ve got bites up and down my leg, which is weird because I don’t normally get bitten at all,” Dalia Kay said.

“I’ve got one on my finger,” Jordan Kay added. “They had like a white marking on them, which kind of in my head actually I thought West Nile virus, you know.”

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The highest concentration of mosquitoes that tested positive was found Huntington, Rozner reported.

“That is because there are more containers that hold water and allow for more mosquito breeding,” Campbell said.

Campbell advises residents to not only remove standing water, but also to clean containers.

“There will be eggs that will be left around the edge of the water level and you want to scrub those eggs away,” Campbell said.

Three birds have died from West Nile this summer but so far, but no humans have been affected. Suffolk County is urging residents to call in any sightings of dead birds, which, experts said, may be a sign of West Nile.

The county said two of the seven people who got infected with West Nile virus last year died.