West Nile Epidemic: How Real Is the Threat?

July 27, 2007— -- First, the bad news: an early spike in the number of cases of West Nile virus infection reported this year has some researchers predicting a possible epidemic as the end of summer approaches.

But don't board up your windows or stock up on bottled water just yet. Infectious disease specialists say such an epidemic would not be as deadly as those involving other viruses -- and would be largely preventable, to boot.

"What we're seeing is the expected increase in West Nile virus transmission that occurs during the summer months," said Dr. Ned Hayes, a medical epidemiologist with the U.S. Centers for Disease Control and Prevention (CDC). But he added that this year, early figures appear high.

According to July 24 data, the CDC has fielded a total of 122 reports of human West Nile Virus infection in 17 states so far this year. Three people have died.

The number of West Nile reports this year so far outstrips the figure recorded at this time last year. Whether this bump will lead to an epidemic this year has yet to be determined, according to infectious disease specialists.

"West Nile virus clearly does have epidemic potential, as demonstrated in years past," said Dr. William Schaffner, chair of preventive medicine at the Vanderbilt University School of Medicine.

"The increase for this time of the year... portends further increases later in the summer to early fall when [West Nile virus infection] usually peaks."

"It is difficult to predict if the trend will continue," said Dawn Wesson, associate professor of tropical medicine at the Tulane University School of Public Health and Tropical Medicine. "Certainly if it does, it could be a bad year for West Nile virus cases and disease."

But while doctors and researchers say it is important to implement preventive measures to stem the surge in infections, a West Nile epidemic would not likely pose the same threat to human life as other viral epidemics, such as those involving influenza.

"The word 'epidemic' is scary," noted Dr. Clifford Bassett, vice chair of the public education committee for the American Academy of Allergy, Asthma and Immunology.