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On the Trail of the West Nile Virus

Some scientists race to develop vaccines against the scourge while others probe the possible lingering effects of the mosquito-borne infection.

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The last major outbreak of mosquito-borne disease in the United States was the 1975 epidemic of St. Louis encephalitis, in which some 2,000 people were reported to have contracted the disease and about 170 to have died. Interestingly, the St. Louis virus epidemic struck many of the same Chicago-area neighborhoods that would be visited by the West Nile virus 27 years later.

 

“This community has been bitten before, so to speak,” said Wichter. Indeed, he took a job in 1977 at the Oak Lawn hospital because he had been intrigued by several cases of St. Louis encephalitis in the community. “I came here because of this St. Louis [encephalitis] experience,” he said with a laugh, “and of course we’ve never seen a case since. So I’ve been waiting for 27 years for something to happen!”

 

Illinois health officials had been on the lookout for West Nile since the spring of 2000, and they identified the first infected bird the next year. In 2002, said Linn Haramis, an entomologist with the Illinois Department of Public Health, authorities began bird surveillance on May 1 “and got our first dead bird on May 2.” By late July, people began showing up in emergency rooms complaining of fever, headache, muscle pain or weakness, stiff neck, sometimes with nausea or a rash; some had severe neurological problems, like mental confusion or an inability to walk. Because public health laboratories became overwhelmed with samples of blood and spinal fluid from suspected hospital cases, and also because the virus takes days to grow in the lab, physicians didn’t get conclusive test results back for two or three weeks. “It was very frustrating,” Wichter recalled.

 

Public concern exploded. In early July, the Illinois Department of Public Health was averaging 4,000 hits a week on the West Nile virus page of its Web site; by September, people seeking information were hitting the page 100,000 times a week. Local residents reported every dead crow. “Don’t send us any more birds!” the Chicago health department urged. Seemingly every animal case of West Nile—lapdog or wolf, sparrow or raptor—made the news. Chicago officials drained neglected residential swimming pools, a prime mosquito breeding site. Cemetery groundskeepers urged mourners not to leave vases at grave sites. City workers fanned out to place larvicide tablets in Chicago’s 210,000 sewer catch basins. Mosquito abatement trucks thrummed through the night spraying pesticides in the city and suburbs.

 

At the height of the outbreak, Wichter addressed the Oak Lawn Chamber of Commerce. Some 150 people crowded into the room to ask the questions that every community wants answered: How much of a risk does this virus pose to human health? What can we do to stop it? Wichter, who is also a professor of neurology at the University of Illinois School of Medicine, didn’t have all the answers. Although health officials recommend killing adult mosquitoes quickly when an arboviral epidemic is under way, Wichter, like many neurologists, is concerned about the potential harmful effects of pesticide use. “The issue of risk-benefit is not very clear,” he told the audience. “Some people will get West Nile fever, and fewer will get meningitis or encephalitis, and fewer still will have permanent disability. Only a minority of a minority will have any residual effects. So if you play that algorithm out, the numbers get really small. Is wholesale spraying justified with a disease of this benignity? You have dogs licking the grass and young children crawling through it. God knows what that will do to the [health] of our community.”

 

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