West Nile virus has continued its inexorable spread westward across the United States and its presence is now confirmed in all states except Alaska and Hawaii. As of October 27, the USDA reported a total of 1192 equine cases throughout the United States, of which 521 were in California and 109 in Arizona.

Information on the incidence of equine cases on a state-by-state basis can be obtained from https://www.aphis.usda.gov/vs/nahps/equine/wnv/map2004.html.

A similar pattern of disease dissemination has emerged in the human population with the Centers for Disease Control reporting on October 26 a total of 2,231 cases, which include 73 fatalities. Arizona reported 379 cases; California, 710; and Colorado, 276. One hundred eleven cases in Arizona and California were identified following screening as presumptive blood donors.

From Equine Disease Quarterly, funded by underwriters at Lloyd’s, London, brokers, and their Kentucky agents