West Nile Outbreak Shaping Up as Worst Ever in U.S., Authorities Say

The nation is heading toward the worst outbreak of West Nile disease in the 13 years that the virus has been on this continent, federal health authorities said Wednesday.

But it is still unclear where and how far cases will spread. Dallas declared an emergency last week, and West Nile deaths have been concentrated in Texas and a few nearby states, including Louisiana, Mississippi, Oklahoma and South Dakota.