In the summer and fall of 2021, West Nile virus spread rapidly through Arizona’s Maricopa County and other areas of the state.
The outbreak, with more than 1,700 cases reported and 127 deaths. was the largest in the United States since the mosquito-borne virus first emerged in this country in 1999. But with the nation facing a far larger public health crisis with the Covid-19 pandemic, it went almost unnoticed.