Other studies have shown horses may only show signs of fever with no other signs. An outbreak of arboviral encephalitis first occurred in New York City in late August and has since been identified in other New York, Connecticut, and New Jersey counties. Prior to and during this outbreak there have been mortalities in crows around the New York City area. The virus was initially identified from bird samples collected at the Bronx zoo. The virus was isolated at NVSL laboratories, and forwarded to the CDC for identification and characterization.
Surveillance is ongoing, and wild bird death reports are being encouraged.
The virus was transmitted to birds by infected mosquitoes and from infected mosquitoes to humans and other animals. There is no evidence that this virus can be transmitted directly from infected horses to humans or to other horses or pets. Based upon published scientific information, viremias in horses are inadequate to infect mosquitoes. Accordingly, restricting the movement of horses is unnecessary to control virus transmission. Preventing exposure of horses to mosquitoes is essential.