The Sacramento-Yolo Mosquito and Vector Control District says several dozen samples of mosquitoes in Davis and Woodland have tested positive for the virus.
Luz Maria Rodriquez with the District says aerial spraying has begun in rural areas of Yolo County and Sacramento County is being monitored closely.
She says recent rain followed by extreme heat creates ideal breeding conditions for mosquitoes.
“When you have the moisture and then the high temperatures, not only does the virus replicate faster but then you also have mosquitoes that are completing their life cycle faster, which means we just have more mosquitoes,” she says.
The number of mosquitoes showing up in the district’s traps is the highest it’s been in a long time.
There’s been one human case of the virus reported so far in Sacramento County.