West Nile virus has been the leading story in the health segment in America for sometime now. And although the number of human cases is quite substantial, it has nevertheless dropped from the peak levels attained around two years ago.
The reasons for this drop are varied. This year 1,299 cases of WNV were reported, down from the 1,386 cases at the same time last year and significantly down from the 4,137 cases in September 2003. The Centers for Disease Control and Prevention has labeled 2003 as the worst year in the history of the West Nile Virus. Nebraska, South Dakota and Colorado were the worst hit areas in that year. This year Colorado has recorded just 48 cases as against the 3,000 reported in 2003, a testimony to the fact that the disease is by far less effective now.
The state Department of Health Services has said that this year, California is the worst affected state with 593 cases out of which nine have so far proved fatal. This figure is more or less similar to last year's figures. However, a large number of birds and mosquitoes have been detected as carriers for the first time. The impact of Hurricane Katrina on the WNV is yet to be assessed, but the fact is that large numbers of birds were also affected by it, so health officials say that perhaps, the impact would not be maximum.
Preventive measures are largely responsible for the drop in numbers, though health officials say that they are unsure if it is the single factor responsible for this decrease. Theresa Smith, an epidemiologist who heads West Nile surveillance for the CDC, acknowledged that preventive measures like using mosquito repellent, such as DEET have helped, but "There probably never will be an ability to predict West Nile."
As far as Colorado's count is concerned, John Pape, who heads West Nile surveillance for the Colorado Department of Public Health and Environment, said that the mosquito population supporting the virus has fallen dramatically even though the state has had a wet spring followed by a hot summer, "Every once in a while every one of these factors that we are just beginning to understand are going to happen the right order, and we'll have a few thousand cases like we had in 2003," he said.
A vaccine for the virus is still in the works and would not be in the mainstream for several years. Therefore this drop in cases is surprising for scientists, yet welcome news for people.
