Early West Nile virus season spikes in US and Europe

Health officials in the United States and Europe are reporting an unusually early and severe start to the West Nile virus season, with multiple deaths and a wide geographic spread of cases. The 2026 transmission period is showing activity far exceeding historical averages before the traditional peak months have even begun.

In the United States, the Centers for Disease Control and Prevention confirmed 48 human cases across 23 states as of June 30, a figure nearly five times the average for that point in the season. Four deaths have been reported, all in Arizona. The last time the season began with similar severity was in 2004. The epicenter of the U.S. outbreak is Maricopa County, Arizona, which had confirmed 29 human cases and all four deaths as of July 1. Local health officials reported 183 mosquito pools had tested positive for the virus as of July 13, indicating widespread circulation. Beyond Arizona, cases have been reported in states including Texas, Colorado, Tennessee, California, and Florida.

Separately, Tarrant County Public Health in Texas confirmed the county's first human case of 2026 on July 24. The patient was diagnosed with the more severe neuroinvasive form of...