Mosquito abatement crews in Fresno County have been spraying insecticide in problem areas.
Any small pool of water can serve as a breeding ground for mosquitoes. Fresno mosquito control crews have also been checking their traps. The mosquitoes are then frozen and sent to a UC Davis lab where they're tested for West Nile.
Gary Byde with Fresno Mosquito & Vector Control said, "West Nile has been a huge concern here in California the last 5 - 6 years and this year seems to be specifically very active."
This year, nine out of 45 samples from the district have tested positive for West Nile. That's two more than in 2011.