No plans to spray insecticide yet, health dept. says
By Tim Hadac
Southwest Chicago Post
The West Nile Virus has been detected in the West Lawn neighborhood—earlier than it usually is each year—but a Chicago Department of Public Health spokesman says the city has no plans to spray insecticide yet.
According to CDPH’s most recent disease surveillance report, West Lawn is one of four of the city’s 77 community areas where the virus has been detected in 2018—joining O’Hare on the far Northwest Side and Riverdale and West Pullman on the South Side.
Despite the finding, CDPH officials have said that the public health risk is low at this point.
While most people bitten by a WNV-infected mosquito will have only a mild illness or no symptoms at all, the disease was an occasional hot topic of discussion at Southwest Side community meetings and in local Facebook groups last year.
The concern is due in part to several severe cases, including that of Jeff Walls, a union carpenter from Garfield Ridge who was laid low by the disease in 2016 and is still struggling to recover—paralyzed and unable to eat or even breathe without assistance.
His story was told publicly in March 2017 by the Southwest Chicago Post. It is unknown whether Walls was bitten by an infected mosquito in Garfield Ridge or elsewhere in the city or suburbs.
In 2015 in Illinois, there were 152 known human cases of disease caused by WNV, with 90 of those scattered throughout Cook County. Statewide, five cases were fatal. The City of Chicago has not released information on its cases.
CDPH’s annual effort rolls out in phases. The first is treating city catch basins—notorious stagnant-water breeding grounds for the Northern House Mosquito, the type of mosquito most closely associated with transmission of West Nile Virus.
This year, CDPH’s contractor, Arkansas-based Vector Disease Control International, is dropping larvicide into 85,000 catch basins on the public way—a task that should wrap up this week.
The larvicide is basically a gut toxin. The [mosquito] larvae ingest the product, it ruptures their gut walls and they die.
Under perfect conditions, the larvicide is long-lasting and will kill larvae in a catch basin for up to six months—more than is needed in Chicago, where the arrival of cold weather essentially ends the West Nile threat each year. A heavy rain, however, can flush away larvicide from catch basins.
The city used to treat all 210,000 catch basins on the public way, but it has been scaled back because some areas of the city—most notably the Loop—have not seen West Nile Virus since it first appeared in Chicago 16 years ago.
On the Southwest Side, catch basins are being treated in an area bounded by 51st Street on the north, 87th Street on the south, Western Avenue on the east and Cicero Avenue on the west. Others are not.
Surveillance is key
CDPH also maintains an active WNV surveillance network. Its backbone is its 83 mosquito traps scattered throughout the city, which are monitored twice weekly for presence of Northern House Mosquitoes—including how many mosquitoes and what percentage are infected with WNV.
When traps indicate a significant amount of infected mosquitoes over two weeks, CDPH rolls out its final weapon: spraying insecticide to kill adult mosquitoes before they can bite and infect people.
Spraying occurs at dusk, when infected mosquitoes are most commonly in the air in search of a blood meal from a person or animal.
Last year, CDPH initially declined to spray insecticide in Clearing and Garfield Ridge, saying the threat to human health was not great enough. Under pressure from 13th Ward Ald. Marty Quinn, CDPH reversed course and sprayed.
CDPH attempts to educate the public each year on what individuals can do to reduce the risk of WNV infection.
First is a campaign to get people to look around their property and eliminate sources of standing water, such as clogged rain gutters, stagnant birdbaths and more.
Second is an effort to encourage people to avoid contact with mosquitoes, such as using insect repellent, wearing certain types of clothing and avoiding going outside at night, when the Northern House Mosquito feeds.