tes in mosquito tissue during the EIP, eventually infecting most of the internal organs including the salivary glands. Once the salivary glands are infected, the mosquito is usually able to transmit the virus to additional hosts during blood feeding. In NYC, these hosts may have included local wild birds: crows, pigeons, sparrows, gulls or as yet unidentified amplification hosts. This would thus establish an amplification and transmission cycle capable of moving virus out of the original transmission focus. The 1999 New York City focus was likely the Whitestone, Auburndale, and Flushing sections in the borough of Queens.Another possibility is that a bird infected with WN virus may have been imported into the city either legally or illegally. Legally imported birds are quarantined for at least 30 days. This should ensure that infected birds do not come into contact with arthropod vectors. Illegally imported birds are not quarantined and may have been a source of virus capable of infecting local mosquitoes. Finally, infected ticks or infected mosquitoes may have hitched a ride on an international air flight and exited at Kennedy International. Infected nymphs or adult ticks could also have hitched a ride while attached to a human traveler or a wild or domestic animal. These ticks might then have dropped off and later fed on a New York animal susceptible to WN virus, thus initiating a NYC transmission cycle. Finally, the virus may have been released accidentally from a legitimate scientific experiment or on purpose as an act of bio-terrorism. The accidental or purposeful release of any mosquito-borne pathogen would require timing that coincides with environmental conditions that favor virus amplification in vertebrate amplification hosts and transmission by suitable vectors, prior to any possible wide-spread transmission of the virus to humans. West Nile viruses possess distinct RNA profiles which can be characterized to discern different ...
