West Nile Virus: The Big Apple bites back

Following the well-publicized outbreak of West Nile Virus in 1999, New York and surrounding areas implemented a multi-tiered attack to avoid a similar crisis in the future. Efforts appear to be paying off; the number of West Nile Virus cases in the New York area has decreased from 62 in 1999 to 14 in 2000, and from seven deaths in 1999 to two deaths the following year.

Carried by birds, West Nile Virus is a form of encephalitis. Mosquitoes become infected when they bite the birds and subsequently transmit the virus to humans and animals.

According to the Centers for Disease Control and Prevention (CDC), based in Atlanta, West Nile Virus has commonly been found in Africa, Eastern Europe, West Asia and the Middle East. It was first detected in the United States in July 1999, when New York was taken by surprise, and it has since been found in birds and animals in New Jersey, Massachusetts, Connecticut, Rhode Island, New Hampshire, Maryland, Virginia and North Carolina.

In New York, the earliest cases of West Nile Virus occurred in Queens, and, as a result, prevention efforts initially focused on that borough. Working with the CDC and the New York State Department of Health, the New York City Department of Health and Office of Emergency Management initiated public education and assistance programs, as well as mosquito control measures and surveillance. In a 1999 address of the New York State Assembly, CDC Entomologist Roger Nasci explained those efforts.

– Public education/assistance During that first wave of West Nile Virus, the city’s priority was to notify the public. In addition to telling residents about the presence of the virus, officials advised residents to minimize their exposure to mosquitoes – either by reducing outdoor activity (particularly during the evening) or by using mosquito repellent. Pamphlets were distributed door to door in neighborhoods where cases had been confirmed. Additionally, the health department issued daily press releases, and the mayor addressed the crisis daily in press conferences.

To assist residents in protecting themselves, the city purchased mosquito repellent and made it available to the public through fire departments and other agencies.

– Mosquito control Efforts to reduce the mosquito population consisted of eliminating habitats for larvae; larvicide application in swimming pools, storm sewers and other areas of standing water; and application of adulticide in areas where mosquito populations were dense. As the number of West Nile cases grew throughout the summer, mosquito control efforts were expanded to cover all of New York’s boroughs.

A fleet of 30 vehicles and a staff of 50 entomologists, technicians, pilots and certified applicators were mobilized to conduct the application. The pesticide Anvil helped control the populations of adult mosquitoes during August and September, when the potential for West Nile Virus transmission was highest. Ground applications were made in New York City and throughout the Northeast, while aerial applications were made only in New York.

– Surveillance Throughout the summer, technicians monitored both larval and adult mosquito populations, and residents were called upon to report dead birds to authorities for testing. Similar monitoring continues, and, last year, localities throughout New York and in Connecticut and New Jersey adopted New York City’s approach to West Nile Virus prevention.

To some degree, the program’s success is proven by the number of cases reported in 2000. “Without question, the efforts in New York State to control the mosquito populations in the Northeast had a significant impact in reducing the number of cases of West Nile Virus in 2000,” says Joel Coats, a professor of entomology and toxicology at Iowa State University, Ames, Iowa. “I think in the future we’ll see the 2000 West Nile effort as a template for other communities faced with problems of large-scale mosquito-borne diseases.

This article was written by Lyell Clarke, president of Clarke Mosquito Control, based in Roselle, Ill. The company assisted New York in planning its control program and applying pesticides.