KNOWLEDGE ABOUT THE factors that cause the spread of West Nile virus has enabled public health agencies to devise methods to prevent the virus from infecting more people and animals.

Since the 1999 outbreak of West Nile virus in the United States, health officials on the national, state, and local levels have formulated extensive plans of action to try to contain the current epidemic and to prevent future outbreaks of the disease.

Prior to the appearance of West Nile virus in the United States, public health departments did not have trained personnel who could handle an outbreak of vector-borne disease. But the federal Centers for Disease Control, along with other agencies like the United States Department of Agriculture, formulated lengthy recommendations once the virus posed a widespread threat.

They issued these recommendations to state and...