West Nile Virus (WNV) is an RNA arbovirus that cycles between
mosquitoes and birds, but also infects and causes disease in
humans, horses and vertebrate species. Although most infections
are asymptomatic, WNV has emerged as the most common cause of
epidemic meningoencephalitis in North America and the leading
cause of arboviral encephalitis in the United States. Mosquitoes
of the genus Culex (Cx.) are the most active vectors of WNV in
North America. Approximately 85% of human WNV infections in the
United States occur in late summer with a peak number of cases
in August and September. Vertical transmission is defined as the
passage of virus from an infected female parent mosquito to her
F1 progeny. Although vertical transmission of WNV has been
demonstrated in the laboratory, confirmation of vertical
transmission of WNV in wild mosquito populations has been
elusive. WNV was first identified in Clark County mosquito
populations in 2004. The Southern Nevada Health District’s
Vector Control office conducts survei