Health officials urge prevention and caution after the mosquito-borne illness was reported in the South Bay.
Jul 29, 2026
Updated 2:42 pm PT
A municipal biologist examines a mosquito in Salt Lake City, Utah, on Aug. 26, 2019. Mosquitos are known for transmitting illnesses like West Nile, which can cause serious health complications. (Rick Bowmer/AP Photo)
Santa Clara County has reported its first two human cases of West Nile Virus in 2026, public health officials announced Wednesday.
West Nile Virus is the most common and most serious mosquito-borne disease in the region, Dr. Krishna Surasi, the county’s assistant public health officer, said.
Common symptoms include fever, head and muscle aches, nausea and vomiting. Severe cases can lead to neurological illness or death.
“These two cases are a reminder that West Nile Virus can cause very serious illness,” Surasi said. “While West Nile Virus is not spread person to person, there are steps the public should take to discourage mosquitoes from feeling welcome in our neighborhoods.”
Contra Costa County Mosquito and Vector Control District technician Josefa Cabada holds a container with mosquito larvae that were found in a retention pond on July 21, 2015, in Bay Point, California.
While most people who are infected experience mild or no symptoms, people over 60 or with certain underlying conditions are at risk of more serious illness.
The infected Santa Clara County residents received treatment and are recovering at home, according to Surasi.
It’s unclear if local mosquitoes infected the patients. Because both traveled domestically during the disease’s incubation period — which is generally between two days and two weeks — the county cannot be sure where they contracted it.