More than 150 samples of mosquitoes in Massachusetts have tested positive for West Nile this summer, but so far there have not been any human cases of the virus in 2025.

West Nile virus activity is on the rise in some northern California counties, according to the Sacramento-Yolo Mosquito and Vector Control District.

Residents are advised to eliminate mosquito breeding sites by removing stagnant water from areas like tires, pools and gutters.