West Nile Virus Outbreak Prompts Widespread Mosquito Alerts in Arizona and California

Public health officials in Maricopa County, Arizona, reported 29 confirmed human West Nile virus cases and four deaths as of July 1, 2026, marking the worst early‑season start in more than two decades. The county, home to over 4.5 million residents, issued an urgent advisory ahead of the July 4 fireworks, urging people to apply EPA‑registered DEET repellent, repair screens, and eliminate standing water. The CDC noted 48 confirmed infections nationwide, nearly five times the historical average for this point in the year.

Meanwhile, Orange County, California, confirmed West Nile‑positive mosquitoes in at least ten cities, including Costa Mesa and Westminster. Although no human cases have been reported this year, vector‑control officials warned residents to use repellents, keep screens in good repair, and regularly dump stagnant water. The heightened mosquito activity was described as “off the charts” compared with the five‑year average.