ABSTRACT
West Nile Virus (WNV) consists of a linear single-stranded RNA (Figure 21.1) and is one species of the Flavivirus genus and Flavivirus family. This genus also includes the pathogens for several human diseases, which will be discussed at the end of this chapter. WNV was not discovered until 1937 when it was isolated from a sick woman living in the West Nile district of Uganda, Africa (the disease and virus were named for the location where they were rst identied). In this chapter, West Nile fever (WNF) is dened as the human disease caused by WNV, including neuroinvasive diseases (i.e., infections of the central nervous system that result in meningitis and encephalitis). The rst recognized epidemics of WNF struck Israel in 1951 and Europe in 1962. Prior to the 1990s, WNV was not known to cause illness in birds, and the symptoms of WNF in humans were mild and complications rare. In Egypt, it was a common childhood illness, and over 80% of adults had antibodies to WNV (Taylor et al. 1956,
Zeller and Schuffenecker 2004). However, the virus morphed in the 1990s when outbreaks of WNF in Europe, northern Africa, and the Middle East were unusually severe and lethal (Rossi et al. 2010). In Romania alone, more than 500 people were diagnosed with WNF in 1996-1997, and 10% of them died. In 2000, 417 WNF patients required hospitalization during a lethal outbreak in Israel; 35 perished. WNF outbreaks still occur sporadically in Europe, including Austria in 2008, Italy in 2009, and Greece in 2010 (Sidebar 21.1). Kunjin virus is a unique type of WNV that occurs in Australia (Hubálek and Halouzka 1999, Zeller and Schuffenecker 2004, Papa et al. 2010).
