After being fairly stable for 3 years, the number of human cases of West Nile virus jumped almost 700% in 2012, according to data released by the Centers for Disease Control and Prevention.
There were 5,674 total cases reported in 2012 – up 697% from 712 in 2011 and the highest since the peak year of 2003, when there were 9,862 cases. The 286 deaths due to West Nile virus that occurred in 2012 were the most in any year in the United States. The previous high was 284 in 2002. The 2,873 cases of neuroinvasive disease also were the highest since 2003, the CDC said.
"Last summer’s outbreak likely resulted from many factors, including higher-than-normal temperatures that influenced mosquito and bird abundance, the replication of the virus in its host mosquitoes, and interactions of birds and mosquitoes in hard-hit areas," the CDC noted.
