CONTRA COSTA COUNTY (KCBS)— Mosquitoes are making their presence felt in the Bay Area almost a month ahead of schedule. The mixed cold-to-warm-to cold again weather has some experts warning it could signal an early start to West Nile virus season.

“We’re seeing a lot of mosquito activity earlier this year than in previous years and it’s primarily weather driven,” said entomologist John Washburn, the interim manager of the Alameda County Mosquito Abatement District.

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Washburn said there’s been a noticeable increase in service calls from people complaining about mosquitos.

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Deborah Bass of the Contra Costa Mosquito & Vector Control District said the early appearance of mosquitos cannot be good.

“The cycle between the warmer weather and the wet weather certainly is a recipe for potentially a bad West Nile season,” she said.

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2014 was a bad year for mosquito-spread, West Nile virus. Nearly 800 human cases were reported in California. 29 people lost their lives, the most since 2004.