CDC Update on West Nile Virus Cases

In a media briefing held today, representatives from the Centers for Disease Control and Prevention (CDC) and the Texas Department of State Health Services presented information on West Nile virus (WNV) case numbers and provided an update on the situation in Texas.

Lyle R. Petersen, MD, MPH, director of the Division of Vector-Borne Infectious Diseases at the CDC,  addressed people's concerns about the spread of WNV: "As we have reported in recent weeks, the number of people reported with West Nile virus continues to rise.  We have seen this trend in previous West Nile epidemics and so the increase we report today is not unexpected.  In fact, we think the reported numbers that will get higher through October.  We recognize that people are worried about the threat of West Nile virus this season. And we want to assure you that we're working closely with state and local governments to contain the outbreak."

According to Petersen, as of Aug. 28, 2012, a total of 48 states have reported West Nile virus infections in people, birds or mosquitoes. Only Alaska and Hawaii have reported no West Nile virus activity. Forty-three states have reported at least one human case of West Nile virus disease. As Petersen explained, "CDC received reports of 1,590 cases of West Nile virus disease in people, including 66 deaths. Of these, 889 (56 percent) were classified as neuroinvasive disease, such as meningitis or encephalitis; and 701 (or 44 percent) were classified as non-neuroinvasive disease.  These numbers represent a 40 percent increase over last weeks report of 1,118 total cases, 629 neuroinvasive disease cases, and 41 deaths.  The 1,590 cases reported thus far in 2012, is the highest number of West Nile virus disease cases reported to the CDC through the last week in August since West Nile virus was first detected in the United States in 1999.  More than 70 percent of the cases have been reported from six states, which in descending order are Texas, South Dakota, Mississippi, Oklahoma, Louisiana, and Michigan.  Nearly half of the cases are from Texas."

Petersen added, "We cannot accurately predict how many human cases will be reported this year.  However, based on current reports, we think the numbers may come close to or even exceed the total number reported in the epidemic years of 2002 and 2003, when about 3000 cases of neuroinvasive disease and more than 260 deaths were reported each year. Because cases of West Nile fever (or non-neuroinvasive disease) are very underreported, we think that cases of neuroinvasive disease are the best measure of the severity of the epidemic. From what weve seen in West Nile epidemics in previous years, we expect that this years epidemic will peak in mid- to late-August. The incidence of infection may peak earlier in southern states than in northern ones."

David L. Lakey, MD, commissioner of the Texas Department of State Health Services, acknowledged that this outbreak is more than just about the data: "We understand that it's more than just the data, that there have been a large number of people whose lives have been changed related to the outbreak of this event. One of the issues that a lot of people wonder about is, 'have we peaked in Texas or not?' At this time, as I look at the data, Im not convinced we have peaked.  We may have plateaued. We are ntensifying our efforts to make sure we control the disease,  especially when seeing increased disease in a different part of the state."

As of Aug. 30, 2012, Lakey reported that Texas has 783 state confirmed cases of West Nile disease, with 31 deaths. There have been 416 cases of West Nile neuroinvasive disease.

"Those numbers are going to continue to go up," Lakey said. "I think we have a lot of reports that are being entered right now and those numbers  will be updated this afternoon. We know that there will be additional cases and deaths entered later today. Assuming normally disease progression, it looks like it's going to be our worst year with West Nile. We have 416  cases of West Nile neuroinvasive cases; in 2003, we had 439. Looking at the progression, this will be on our worst year.  In 2003, we had 40 deaths. Again, we're at 31 so far this year. So we're closely evaluating the disease incidents  from all counties in the state of the Texas, but focusing on certain counties that have been hardest hit."

For specific data for any county in the state of Texas, visit: www.tx.westnile.org.