New York State West Nile Virus Response Plan

INTRODUCTION

This document is the 2001 plan that the New York State Department of Health has developed by working in conjunction with other state agencies, local health units, and the Centers for Disease Control and Prevention to minimize the impact of West Nile virus in New York State.

This plan is a guidance document for local health units and other governmental agencies. It does not direct local health units to take particular actions. Rather, it describes those steps that, at this time, are considered to be most effective in protecting public health and the environment. Because our understanding of West Nile virus, while growing, remains incomplete, changes to the plan, as new information is acquired, are anticipated.

The outbreak of West Nile virus encephalitis in the New York City metropolitan area in the summer and fall of 1999 was an unprecedented event. After the initial outbreak in 1999, it was not certain if the virus had run its course or if the cycle of infection would begin again when mosquitoes emerged from hibernation. To prepare for its possible recurrence, New York State organized a series of work groups in the winter of 1999-2000, which included representatives from New York State agencies, local health departments, New York City officials, and representatives from community, environmental and other non-governmental organizations. The result of that effort was the 2000 New York State West Nile Virus Response Plan; the Plan emphasized surveillance, public education, and a hierarchical response for the management of mosquitoes.

Not only did West Nile virus persist through the winter, the virus spread rapidly throughout New York State and the northeastern United States in the summer and fall of 2000. By the end of the mosquito season, all but one county in New York State had documented West Nile virus activity. Fourteen New York City residents were hospitalized due to West Nile virus infection. In addition, West Nile virus infection was confirmed in 1,263 birds, 366 mosquito pools and 26 mammals.

After the 2000 outbreak, the New York State Department of Health reconvened the work groups to revise its response plan and to incorporate the valuable lessons learned during the past mosquito season. The result is the following revised plan, which includes five major sections: prevention, response and control; mosquito surveillance; bird and mammal surveillance; human surveillance; and public communications. Important changes from the previous plan are highlighted in the beginning of each section.

This plan is based on the realization that control measures are unlikely to eradicate West Nile virus from New York State. Therefore, the goal is to prevent amplification of the virus to the extent that it places humans and domestic animals at risk of serious illness. Evidence from human serosurveys that were conducted in 2000 showed that the risk of human infection and illness is quite low, even when West Nile Virus is present in the environment. It appears that humans are at greatest risk of serious illness in areas of extraordinary amplification of West Nile virus as a result of transmission among birds and mosquitoes. Therefore, this plan is based on the approach of conducting careful surveillance to detect when West Nile virus is present and increasing, and then to conduct a graded response appropriate to the level of human threat. As the threat increases, the public health response changes from public education campaigns, mosquito larval habitat reduction programs, and larval control, to higher levels of education and enhanced larval control activities. Mosquito adulticiding is reserved for those situations where there appears to be imminent risk to human health.

Implementation of this plan will require the dedicated cooperation and participation of local, state and federal agencies, community organizations, and the public. With a coordinated response, the overall goals of this plan will be achieved by minimizing the risk of West Nile virus illness in humans and domestic animals through use of a graded response that causes the least adverse impacts on the environment.