Transmission and Life Cycle

The West Nile Virus is most commonly carried through mosquitos. It is transmitted when a mosquitto bites an infected bird. The virus travels through the mosquito's salivary glands into the circulatory system where it remains for a few days. It can then be released when the mosquito bites another organism. The organism which the virus is passed onto is only contagious if they are able to develop a high enough concentration of the virus in their blood (3). Its host range consists of mosquitos, birds, horses, humans, and other species (5). Birds and mosquitos are contagious, while other organisms which cannot spread the virus to other living things, such as humans and horses, are known as "dead end organisms" (3). Humans typically contract the virus from mosquitos, though 43 other species, including ticks, have been reported to serve as vectors (1).

Figure 2.1: Transmission Cycle of West Nile Virus (3).

Figure 2.2: The Culex genus of mosquitos, which serves as a primary vector in the United States (1).

Like all viruses, the West Nile Virus can only replicate in host cells because it lacks metabolic enzymes and equipment for making proteins. The virus infects a host cell by fusing to its plasma membrane, inserting its viral genome. Once inside, the protein the virus encodes can reprogram the cell to copy the viral nucleic acid and manufacture viral proteins (5).