Officials have confirmed five mosquito samples from both Sacramento and Yolo counties tested positive for West Nile Virus.
"Normally, we don't see our first positive mosquito samples until June or July so this is significantly earlier than previous seasons."
Luz Maria Rodriguez is with the Sacramento-Yolo Mosquito and Vector Control District. She says the earlier discovery could signal a longer and very busy mosquito season.
Two new dead birds have also tested positive for West Nile.
"The dead birds - one of them was in Elk Grove and then the other was in the Gerber and Bradshaw area of south Sacramento County."
Rodriguez says in response, the district is stepping up mosquito trapping and surveillance in the area to find locations where the pests may be breeding.