States Prepare for West Nile Season

Health officials hope educating the public will help head off the virus.

ByABC News
February 10, 2009, 6:28 PM

May 26, 2008— -- SIOUX FALLS, S.D. (AP) - Officials have found that controllingWest Nile virus is as much about educating the public as it iskilling mosquitoes.

South Dakota, with the nation's highest rate of seriousinfections, is entering its seventh summer of the sometimes fatalvirus that is transmitted by mosquitoes from infected birds tohumans.

Not every mosquito species transmits the virus. Early in springit's a nuisance mosquito called Ades vexans that's bothering peoplein the eastern part of the state but seldom carries the virus. It'sfirst to show up because eggs laid in fall hatch in spring.

"Just add water and poof, you've got mosquitoes," said MikeHildreth, a professor and researcher at South Dakota StateUniversity.

But the real threat of West Nile virus comes later in summerfrom the Culex tarsalis mosquito, which lays eggs in the spring andneeds to repopulate and find infected birds before it turns itsattention to humans.

That's why the number of human West Nile cases generally peaksin the second week of August and why public policy and personalprecautions often are driven by the less-dangerous nuisancemosquito that shows up earlier.

"Last year, with the dry summer, what we were hearing frompeople is, `There's no mosquito problem, why are you spraying?',and yet the tarsalis, which handles the drier conditions much, muchbetter, was in plentiful numbers," Hildreth said.

South Dakota had 208 human infections and six deaths last year.Twenty-six people have died in South Dakota from West Nile since itfirst appeared in 2002. More than 300 have developed the seriousneuroinvasive complications of encephalitis and meningitis.

The virus already is circulating in some states. Human caseshave been reported in Arizona, Mississippi and Tennessee, said LonKightlinger, epidemiologist in the state Health Department.

South Dakota's per-capita rate of serious complications fromWest Nile is the highest in the nation. Wyoming ranks second,Nebraska third and North Dakota fourth, Kightlinger said.