In August 1999, several reports of New Yorkers finding dead birds coincided with Veterinarians treating crows with an undiagnosed neurological disease. While awaiting analysis on necropsy of some of the crows, six exotic birds died at the zoo. At the same time, the Chief of Infectious Diseases noticed increased numbers of spinal taps being performed in human patients admitted with meningoencephalitis. Two elderly patients died, and their brains were submitted for further testing to try and determine the cause of the disease.
By the start of September, 2 weeks later, an outbreak of an unknown disease in New York was announced, and a hotline was established, with up to 40 suspected human cases. Eventually it was considered that the dying birds and the outbreak in humans could be linked, resulting in 400 birds being examined for necropsy. After extensive testing for poisons, bacteria and viruses all gave negative results, testing for exotic diseases began. It was eventually confirmed that the responsible disease was a virus, West Nile Virus, which until that point had never been seen in the Western Hemisphere. WNV is a zoonotic virus transmitted by mosquitos, with birds acting as an amplification host. One Health collaboration may have lead to a faster diagnoses, as it took veterinarians and human physicians time to begin to collaborate and communicate their findings and put all the pieces together.