West Nile Virus case total continues to grow
by Wyoming Department of Health
September 3, 2007
The 2007 West Nile virus infection case count in Wyoming residents continues to grow at a steady pace with 119 cases reported so far to the Wyoming Department of Health.
Eleven of Wyoming’s 23 counties have reported West Nile virus cases this year. Of the 119 reported cases, 85 have been among Fremont County residents. There have also been 13 cases reported in Campbell County; seven in Sheridan County; five in Goshen County (includes one death); two each in Crook and Natrona counties; and one each in Hot Springs, Laramie, Park, Washakie and Weston counties.
According to Dr. Tracy Murphy, state epidemiologist with the Wyoming Department of Health, a number of factors can affect how case numbers are interpreted. “There is variability around the state in how aggressive healthcare providers are regarding West Nile virus testing,” he said. “We know many cases are not diagnosed because ill people do not seek care and because some medical professionals do not pursue testing.”
Most people infected with West Nile virus do not develop symptoms. Of those who become ill with what’s called “West Nile fever,” symptoms include fever, headache, body aches, skin rash and swollen lymph nodes. A very small percentage of infected persons develop West Nile neuroinvasive disease (meningitis or encephalitis). Nine of this year’s reported cases in the state (7.6 percent) have been of this type. Symptoms include severe headache, fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions and paralysis.
Murphy said West Nile virus neuroinvasive disease is more likely to be diagnosed because people become quite ill. “As a result, they are more likely to see a doctor and to be tested,” he explained.
“Further analysis of the neuroinvasive disease rates suggests there is likely not as big a disparity of West Nile virus infections among several counties as the overall number of reported cases would suggest,” Murphy said. It is estimated there are about 150 infections for every case of neuroinvasive disease.
The age range for the reported cases is 11 through 86, with a median age of 48. Females account for 53 percent of the cases and males are at 47 percent.
“We continue to recommend people keep mosquitoes away by using an insect repellant and wear appropriate protective clothing when spending time outdoors,” Murphy said. Avoiding the outdoors at dawn and dusk and draining standing water are also important prevention strategies. Mosquitoes spread West Nile virus after they feed on infected birds and then bite people, other birds and animals.
In 2006, 65 human cases and two deaths were reported in Wyoming. There were 12 human cases with 2 deaths in 2005; 10 human cases with no deaths in 2004; and 393 human cases with 9 deaths in 2003.
More West Nile virus information is available at http://www.badskeeter.org/ or by calling 1-877-WYO-BITE.