The deadly West Nile virus is spreading across the United States faster than usual this year, spurred by a mild winter and a hot spring that has bred a surge of early-season mosquitos.
The Centers for Disease Control and Prevention said 56 cases of human infection had been reported through Tuesday, the highest number at this point of the summer since 2004. Most of those cases, 44, have been cases of severe neuroinvasive disease, which presents the highest risk to humans.
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