CDC: Division of Vector-Borne Infectious Diseases, West Nile Virus
WNV is an arbovirus, short for arthropod borne virus. WNV resides in bird reservoir hosts and is spread to incidental hosts like cats, dogs, horses and humans, primarily by mosquitoes, although it has been found in ticks. As birds migrate, they transport the virus to new mosquito populations. Mosquitoes feed on bird blood, the virus reproduces, and the cycle continues. In the United States, West Nile virus has resulted in the largest arboviral meningoencephalitis epidemic documented in the Western Hemisphere and the largest reported epidemic of West Nile related viral encephalitis.
Humans have a small but important role in the transmission of WNV. WNV can reside for a short time in the blood and tissue of asymptomatic humans. Therefore, exposure to infected blood and body tissue can transmit the disease. Transmission of WNV is possible through blood transfusion, needle stick, tissue transplant, transcutaneous exposure, breast feeding and transplacental inoculation. WNV is yet one more reason for the strict adherence to Blood and Body Fluid Precautions.
CDC: Division of Vector-Borne Infectious Diseases, West Nile Virus