WNV Remains Leading Cause of Arboviral Disease in Continental US

West Nile virus (WNV) remained the most common cause of neuroinvasive arboviral disease in the continental United States in 2023, according to findings published June 12 in Morbidity and Mortality Weekly Report. The report summarizes surveillance data reported to Centers for Disease Control and Prevention by U.S. jurisdictions for six nationally notifiable arboviruses: WNV, Powassan, La Crosse, Jamestown Canyon, St. Louis encephalitis and eastern equine encephalitis viruses.

In total, 48 states and the District of Columbia reported 2,770 confirmed domestic cases of arboviral disease, including those caused by WNV (2,628, 95%), Powassan (49, 2%), La Crosse (35, 1%), Jamestown Canyon (27, 1%), St. Louis encephalitis (21, 1%), eastern equine encephalitis (seven cases, less than 1%) and unspecified California serogroup viruses (three cases, less than 1%).

The authors noted that the 2023 case count more than doubled compared with 2022 (1,247 cases), largely driven by a 132% increase in reported WNV cases. Although La Crosse virus was the most common cause of neuroinvasive arboviral disease among children, WNV continues to cause the highest overall burden, with more than 2,000 cases reported in seven of the past 10 years.

According to the authors, the report highlights the ongoing threat of WNV transmission through organ transplantation. In 2023, three cases of WNV, including one death, resulted from organ transplants received from two asymptomatic donors. Since 2018, a total of four transplant-related clusters have been identified, resulting in eight infected recipients and three deaths.

“These reports underscore the ongoing risk for transmission through solid organ transplantation associated with high morbidity and mortality and the need to potentially screen organ donors for the presence of viral RNA during periods of elevated WNV risk,” they concluded.

Additional information about the six nationally notifiable arboviruses is available in AABB’s emerging infectious diseases fact sheets.