Risk of West Nile disease builds in fall

Labor Day weekend is not only the last weekend of summer — historically it is a dangerous time for exposure to the West Nile virus in Missouri. With four human cases reported in the last week, state health officials caution residents that the virus is not going away.

West Nile cases increase in the late summer and early fall. In the past several weeks, dead blue jays that tested positive for the virus have been found in northwest and southwest Columbia, according to the Boone County Health Department. Although there have yet to be any human cases of infection in Columbia, the threat of the virus remains.

“We’ve had four positive birds so far, no humans and no horses,” said Stephanie Browning, director of Columbia Boone County Health Department. In Missouri, the number of dead birds testing positive for the virus has increased by nearly 70 percent in recent weeks.

Nearly half of Missouri’s human cases last year were infected around the Labor Day holiday. Browning expects this year’s reported cases to increase in the coming months. The state health agency is warning people to avoid being outdoors at dawn and dusk, when mosquitoes, the insects that spread the disease, are most active.

As rainfall increases and weather cools down, mosquitoes are not only more active, they are reproducing, said Dr. Howard Pue, Missouri State Public Health Veterinarian. In fact, Pue said, this summer’s lack of rain may cause mosquitoes to reproduce with more vigor.

“Mosquitoes are definitely not an endangered species,” Pue said. “They will sustain their population.”

So far this year, human cases were reported in Putnam, St. Louis and Jackson counties and in St. Louis. AlthoughColumbia is not on this list, Karen Yates of the Missouri Department of Health and Senior Services cited the recent rain as cause for concern. In particular, standing water left in flowerpots, gutters and other places is an attractive place for mosquitoes to breed.

DHSS is advising people, when outdoors, to wear pants and long-sleeved shirts and use insect repellents containing DEET. Exposure to West Nile virus could produce flu-like symptoms, including high fever and severe headache. It usually takes about two weeks for symptoms to appear, although health officials said that some infected people may not have any symptoms at all.