Mosquitos are known for transmitting illnesses like West Nile, which can cause serious health complications. Mosquitos are known for transmitting illnesses like West Nile, which can cause serious health complications. Santa Clara County has reported its first two human cases of West Nile Virus in 2026, public health officials announced Wednesday. “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.”