Summary: <p>Tampa, Fla., Mayor Bob Buckhorn said he was prepared to call off the Republican National Convention next week if Hurricane Isaac threatens public safety. The housing market showed more signs of recovery as home sales rose in July. And U.S. health officials said the West Nile virus outbreak in five states was one of the worst in American history. Naftali Bendavid of The Wall Street Journal, Jeanne Cummings of Bloomberg News and David Chalian of Yahoo! News join Diane for analysis of the week's top national news stories.</p>
