News

If historical trends hold true, the West Nile virus epidemic peaked some time in August, although numbers of cases continue to increase because of lags in detection and reporting.

As of Sept. 11, the CDC had received reports of 2,636 cases of West Nile virus disease, with 118 deaths, up from 1,993 cases and 87 deaths last week. The virus has been detected in humans in all but five states and has been found in humans, birds, or mosquitoes in every state except Hawaii and Alaska.

Slightly more than half of the reported cases (1,405) involved neuroinvasive disease. That's the highest number of such cases reported through the second week of September since the virus emerged in the U.S. in 1999.

And the number of neuroinvasive cases -- the best indicator of the size of a West Nile epidemic -- is expected to meet or exceed the previous record of 2,946 in 2002, Lyle Petersen, MD, MPH, director of the CDC's division of vector-borne infectious diseases, said Wednesday on a conference call with reporters.

The same trend is expected for the number of deaths, keeping the current outbreak on track to be the worst on record, Petersen said.

Although there were more total cases reported at this time of the year in 2003, Petersen said that that was an artifact of excessive testing for non-neuroinvasive disease by a single state that year.

"One good piece of news is that, based on historical data, ... we've turned the corner on the epidemic," he said. "We're hopeful that the worst of the outbreak is behind us."