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West Nile cases hit 10 in county; hot month extends biting season

Sep 6, 2013 - By Katie Roenigk, Staff Writer

At least 10 Fremont County residents have contracted West Nile Virus this season -- far more than in any other area of the state.

One man in Park County has died of the virus, according to the Wyoming Department of Health, and Platte and Natrona counties each reported one non-fatal case.

"We have definitely seen an uptick in WNV cases in Wyoming over the last few weeks," WDH surveillance epidemiologist Emily Thorp said Tuesday.

Most West Nile cases are believed to go unreported, so the actual number of infected people could be much higher.

By the end of last summer, seven human cases of WNV had been recorded in the state, including two in Fremont County. None of the bugs trapped in Fremont County tested positive for the virus last year, either, but in 2013 WNV has been detected in mosquito populations throughout the local area.

"This has been a long, hot year, and those temperatures really promote the (transmission of) West Nile," said Nancy Pieropan, a member of the Fremont County Weed and Pest biological control staff. "You have to have nice, warm temperatures for the disease to amplify in the mosquito itself before it can be transmitted to other hosts."

The Centers for Disease Control and Prevention says most people infected with WNV will have no symptoms, but 20 percent of people will develop a fever, and less than 1 percent of infected people will develop a serious, sometimes fatal, neurological illness.

End of season

Mosquito numbers are dwindling as the summer season approaches its end, and no WNV was detected in Riverton during trapping operations last week. But Pieropan said people still need to protect themselves from being bitten by the bugs.

"Even though I didn't find any (WNV) in the Riverton area, that doesn't mean there's not any there -- I just didn't catch any," Pieropan said Tuesday. "People should still be behaving like there's risk of getting West Nile, because there certainly still is."

Mosquitoes can remain active into October.

On Aug. 29, only 10 mosquitoes were trapped on Davis Lane in Riverton, but nine of them were Culex tarsalis, the type of bug that carries WNV. Those did not test significantly positive for the virus, however.

On Jackson Avenue, five female mosquitoes were trapped Aug. 29, including one Culex tarsalis. Again, no WNV was detected.

Positive hits

On Aug. 28, mosquitoes trapped on Carbine Lane in Lander and Ohio Street in Hudson tested positive for WNV.

Earlier in the month, on Aug. 14, mosquitoes on Davis Lane, Jackson Avenue and North Smith Street in Riverton all tested positive for WNV. And for the past five weeks, test results in the Arapahoe area on Mission Lane have shown positive results for the virus.

Pieropan said this will be the last week of mosquito testing through the Weed and Pest group for the season, but she encouraged people to stay vigilant about the bugs until cooler weather comes. Officials say residents should wear bug spray and long sleeves and try to stay indoors during dawn and dusk when mosquitoes are most active.

"The mosquitoes out flying around now could very well be transmitting West Nile," Pieropan said. "Continue to be cautious. ... It's in the system and will remain in the system until the system shuts down for the winter."

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