As West Nile Virus Cases Rise, Vaccine Still Far Off

Nancy A. Melville

September 17, 2012

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September 17, 2012 — As 2012 appears to be heading to the record books for the worst outbreak of West Nile virus since the disease was first detected in the United States in 1999, a vaccine and antiviral treatment for the virus remain elusive.

According to the Centers for Disease Control and Prevention (CDC), a total of 1405 cases of West Nile virus neuroinvasive disease have been reported to the agency in 2012, as of September 11, representing the highest number of cases reported through the second week in September since the virus was first recognized in 1999. Of those cases, 118 resulted in death.

Including neuroinvasive and nonneuroinvasive cases, a total of 2636 cases have been reported, the highest rate through the second week of September since 2003. However, CDC officials say the severity of a West Nile outbreak is more reliably measured according to neuroinvasive disease reports.

"We consider neuroinvasive disease the best indicator of the scope of the epidemic, since these cases are most consistently reported, and thus we still continue to believe that this year's outbreak is the most serious outbreak to date since West Nile virus was discovered in the United States," Lyle Petersen, MD, MPH, director of the CDC's Division of Vector-Borne Infectious Diseases and the National Center for Emerging and Zoonotic Infectious Diseases, said in a press briefing this week.

Dr. Petersen noted that because West Nile virus outbreaks in the United States tend to peak in mid- to late August, the worst may be over, and the peak of the epidemic may have passed.

However, the size of this year's outbreak puts a spotlight on the question of why neither a vaccine nor an effective treatment for the virus is available after all these years.