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.

Officials say while most people infected with West Nile Virus have no symptoms or only mild flu-like symptoms, some people will develop a more severe form of the disease affecting the nervous system,...