In the US, the highest incidence of POWV is in Minnesota and Wisconsin, with Massachusetts and New York also having higher incidence than other states in the Great Lakes or Northeast region. POWV was included in the list of nationally notifiable diseases to the U.S. Centers for Disease Control and Prevention (CDC) in 2002. Between 2009 and 2018, 133 cases of neuroinvasive POWV and 12 cases of non-neuroinvasive POWV were reported to the CDC. Since its discovery in 1958, there have only been 150 reported human illnesses caused by POWV. The incidence rate of POWV in the United States was 1 case per year from 1958-2005, and has risen to an average of 10 cases per year since then.