To kill an infestation of disease-laden mosquitoes in mid-1999, New York city authorities authorised the continuous spraying of Malathion, a known toxic chemical, to kill the mosquitoes. It was deemed necessary to spray the general pollution and city areas to spray to stop the spread of Japanese Encephalitis, the 4th incarnation of the alleged virus borne by the mosquitoes. The strain was first identified as St. Louis Encephalitis, then West Nile Encephalitis, then West Nile-like, and finally Japanese Encephalitis. Each variety of the disease is carried by mosquitoes.