Health Highlights: Aug. 17, 2004 Here are some of the latest health and medical news developments, compiled by editors of HealthDay:    -----     Arizona Leads Nation in West Nile Cases      Thousands of abandoned swimming pools, along with irrigation canals and other prime breeding sites for mosquitoes in Phoenix, have made Arizona the state hardest hit by West Nile virus this year.      Arizona has accounted for at least 290 of more than 500 reported cases of West Nile virus in the United States so far in 2004...