NewsDesk  @infectiousdiseasenews

The Utah Department of Health reports at least 11 Utah residents in Salt Lake, Davis, and Weber counties have been diagnosed with West Nile virus (WNV) this season, (nine neuroinvasive, and two non-neuroinvasive), one death has occurred in the Weber/Morgan Health district, and five additional cases are pending confirmation.


While most people infected with West Nile virus don’t develop any symptoms, about one in 150 people develop a severe illness that affects the central nervous system. Among patients with neuroinvasive disease about one in 10 die.

According to Hannah Rettler, Utah Department of Health (UDOH) Vectorborne/Zoonotic Epidemiologist, “Utah is now seeing the highest number of mosquito trap sites test positive for WNV than we’ve had in the history of West Nile surveillance in the state. As of August 23, 2021, 8% of mosquito trap sites tested positive for WNV (506 out of 5,906 total sites). For reference, in 2020, 0.008% tested positive and in 2017, the year with the highest number of human WNV cases (62), 8% of mosquito trap sites tested positive for WNV.

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“West Nile virus is an annual presence in Utah and it isn’t going away,” adds Rettler. In addition to the human cases, nine horses have tested positive for West Nile virus, two crows, two sentinel chickens, one magpie, one scrubjay, and one red-tailed hawk. Rettler worries, “We could see many more Utahns become ill unless residents take steps to reduce mosquito exposure.” Utah records an average of 12 human cases of West Nile virus each year, ranging between two and 21 cases. In 2019, there were 21 human cases, and in 2020 there were two.

According to the Centers for Disease Control and Prevention (CDC), more than 200 WNV cases have been reported in 29 states, including 10 deaths.

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