Reported human infections of West Nile Virus this year have exceeded those from 2005.

The latest figures from the North Dakota Department of Health show human cases at 112, up from 84 reported the previous week. This is 26 more cases than the 86 human cases reported in 2005.

"Of the 112, we looked at when the majority became ill, and it was the first week of August," said Michelle Feist, West Nile virus surveillance coordinator for the state.

There is a lag time from the when a person is infected and when a person exhibits symptoms, Feist said. It takes three days to two weeks for a person to show symptoms. Then it can take up to a week for test results to come back, she said.

In previous years, the peak of the West Nile virus season was the last week of August or the first week of September.

Only one death has been linked to the virus this year. It was a man from the southeastern part of the state who was in his 60s. He was hospitalized and had underlying medical issues.

About a fourth of the people infected with the virus, 25 to date, have been hospitalized. More men than women have tested positive for the virus, and 65 percent of the people who tested positive are 40 or older. People in their 40s have accounted for most of the cases, at 31.

The best way to prevent a West Nile infection is to not get a mosquito bite, Feist said. Staying indoors at dusk and dawn, when mosquitoes are most active, using insect repellent with DEET and wearing long-sleeved clothing and pants when outdoors helps, she said.

Most people who are infected with West Nile - up to 80 percent - do not show symptoms. Those who do have a range of symptoms, from body ache, nausea and headache that can vary in severity, Feist said. The most severe cases of West Nile can cause encephalitis or meningitis. It can result in death.

The forecasted cool weather for this weekend could put a dent in the mosquito populations, which have been low compared to previous years.

"The first hard freeze could kill the adults," Feist said. "Also, they could seek shelter."

As the weather cools, some will die off, she said. The mosquito that is the primary cause of transmitting the virus to humans is the Culex tarsalis.

The North Dakota Department of Health provides weekly updates on the number of confirmed cases of West Nile.

(Reach reporter Sara Kincaid at 250-8251 or sara.kincaid@;bismarcktribune.com.)