A crow had been found with the virus in Grand Forks on Monday, and test results came back positive Tuesday.
Grand Forks health officials are warning the public to protect themselves against mosquito bites after the first North Dakota case of West Nile virus was found Tuesday and the number of mosquitoes that can transmit the disease has risen.
The percentage of culex mosquitoes, the most common species to transmit the virus and one of the most common mosquitoes in the region, jumped from an average of 15 percent of total mosquitoes to 58 percent on Monday, said Todd Hanson, supervisor of Grand Forks Mosquito Control.
A crow had been found with the virus in Grand Forks on Monday, and test results came back positive Tuesday, but Hanson would not identify exactly where the bird had been found.
After a mosquito feeds on an infected bird, it can pick up the virus and transmit it to humans and other mammals as well as noninfected birds, according to the Grand Forks Health Department.
No major change
No major change to mosquito control will be made in response to the elevated risk because Grand Forks Mosquito Control operates as if the virus were always present, according to a news release by the Grand Forks Health Department.
Several factors can trigger a spraying, such as weather conditions and a high percentage of culex in a low number of total mosquitoes, he said. Under normal conditions, the city requires an average of 75 mosquitoes per trap to spray for nuisance control.
“We’ve been spraying based on our trap counts, primarily for nuisance control,” Hanson said. “Last week we started seeing an increase in the culex, and now we’re focusing more on spraying for the West Nile virus.”
The culex species can carry other viruses such as St. Louis encephalitis and typically starts to appear in the city’s traps in late June.
Symptoms and cases
Most people infected with the West Nile virus, which can be fatal, do not develop symptoms.
Still, a mild illness with symptoms such as fever, headache, body aches and swollen lymph nodes can develop in some people one to two weeks after exposure, according to the Grand Forks Health Department.
Although less than 1 percent of infected people can develop encephalitis — an inflammation of the brain identified by high fever, headache or neck stiffness — Hanson warns that the virus kills people each year.
“One person actually died this year from the West Nile virus they got last year,” he said.
Generally, the number of animal and human cases reported across the state has been sporadic since 2008, according to the North Dakota Department of Health.
Last year a total of 89 were reported, the highest in five years. People ages 60 and older made up the majority of cases, and people in that age bracket are most vulnerable to getting the virus. In previous years, cases ranged from one in 2009 to 37 the year prior.
The most important thing for the public is to avoid mosquito bites, and the best way to do that is by wearing repellent with DEET and avoiding dusk, as the culex species is most active at night, Hanson said.
“Eliminate any standing water around your home,” he said. “Mosquitoes will lay eggs in a cup of water.”