A spike in the number of mosquitoes in the Sacramento region over the past few weeks is raising worries about a more dangerous than usual return of West Nile virus.
Recent rains in the region followed by unseasonable heat have created ideal conditions for mosquitoes to thrive, reported the Sacramento-Yolo Mosquito & Vector Control District this week. As a result, West Nile virus, mostly transmitted from infected mosquitoes to humans and animals, is expected to arrive earlier than usual this year. The district has responded by already testing dead birds and mosquito samples that may contain the virus.
“We are seeing a definite increase in the number of mosquitoes collected in the traps set out by our laboratory staff,” said District Manager Gary Goodman in a news release. “This is very significant, especially when you consider that it’s only the beginning of May. The mosquito season is just getting started, and it looks like it will be a very busy one.”
The California Department of Public Health confirmed last week the state’s first human case of West Nile virus this year in Kings County. The department previously announced it had recovered three dead birds carrying the virus, from Orange, San Diego and San Mateo counties.
“As people started moving around globally, not only pathogens but also mosquitoes started moving with them, too,” said Gregory Lanzaro, a pathology professor and researcher at the UC Davis School of Veterinary Medicine. “We are getting them out of the places they evolved to places where they have never been before.”
The Sacramento region’s vast rice fields and other farmland produce hefty numbers of mosquitoes each year, Lanzaro said. This year’s mosquito surge has also been helped along by lingering puddles and other moisture that have provided more habitats for the insects.
Most infected humans do not develop symptoms from the virus, but less than 1 percent can develop serious, possibly fatal neurological illnesses such as meningitis, according to the Centers for Disease Control and Prevention. The CDC reported that California saw 424 people infected and nine dead from the virus last year.
The local vector control district is asking the public to use effective insect repellent while outdoors and to dress in long sleeves and pants. The district is also advising residents to secure window screens and drain any standing water, where mosquitoes may breed.