It is not believed that the virus is present in high enough numbers or for long enough to reinfect another mosquito if the infected person or animal was bitten again. Conversely, it is always possible that a mosquito could transmit the virus from one person to another, but this would be virtually impossible to trace. Until recently, it was believed that only mosquitos could transmit the disease, but evidence now indicates that crows can transmit the virus to other crows in the absence of mosquitos as demonstrated in an experimental study 3 . Virus numbers are very low in the blood and this viremia is short lived. In light of this, it is believed that horses and humans are dead end hosts, and that the disease needs mosquitos to be transmitted.
Histological lesions are similar to other arboviruses and herpesvirus encephalopathies.
Most commonly, mild to moderate non-suppurative encephalomyelitis and vasculitis with perivascular cuffing have been described, and may include multifocal necrosis of affected tissues. Usually the lower brainstem and ventral horns of the thoracic and lumbar spinal cord are affected, while the cerebellum and cortices may not be. The dura may be thickened and submeningeal edema may be present. Back to Home Prevention and Control of WNV Major prevention involves moquito and tick control if you are living in or travelling to a West Nile virus positive area. Sentinel chickens have been stationed along the Atlantic Flyway and are tested routinely.