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City Services

June 14, 2017

City Health Department Encourages West Nile Virus Prevention

People age 50 or older are at greater risk of becoming seriously ill with WNV

CHICAGO - The Chicago Department of Public Health would like to remind people, especially those spending time outdoors, to protect themselves from mosquito illness by taking a few precautionary steps.

"While the number of West Nile-related illnesses in Chicago has been low in the last couple of years, we’re maintaining our vigilance with West Nile Virus and are asking residents do the same,” said Chicago Department of Public Health (CDPH) Commissioner Julie Morita, M.D. “Early, repeated and effective prevention strategies are crucial to reducing human risk from West Nile virus.”

West Nile Virus infection can cause an illness called West Nile Fever, characterized by fever, muscle aches, rash and headache. West Nile Fever can sometimes be a significant illness, with lingering weakness and fatigue lasting several weeks. More severe West Nile illness is less common, but can include meningitis (inflammation of the membrane surrounding the brain) and encephalitis (inflammation and swelling of the brain itself).

Human infections occur when people are bitten by a mosquito carrying the virus. On average, only about two in 10 people who are bitten by an infected mosquito will actually become ill. People at most risk for developing WNV illness include those of advanced age, or with chronic health conditions or compromised immune systems.

“The key to controlling West Nile Virus is reducing the population of Culex pipiens, commonly known as the Northern House Mosquito,” added CDPH Environmental Health Medical Director Cortland Lohff, M.D. “This mosquito commonly lays its eggs in containers of standing water. Many of these containers are the types of things that are found in many backyards and other places around homes. That makes it imperative that individual Chicagoans get involved, look around their yards and neighborhoods, and identify and eliminate sources of standing water.”

CDPH officials are asking everyone to help thwart the insects by:

  • Eliminating standing water that lasts more than four days.
  • Turning over wheelbarrows and plastic wading pools when not in use.
  • Cleaning and chlorinating swimming pools and keeping water from collecting on pool covers.
  • Removing items that may hold water, including buckets, metal cans, plastic containers, old tires, bottles, jars, cups, and saucers placed under flower pots.
  • Ensuring that rain gutters and downspouts are not clogged.
  • Changing the water in birdbaths and pets’ water bowls every three to four days.
  • Keeping grass and bushes trimmed, and filling in low spots on lawns.
  • Checking to see that all screen on doors and windows are tight-fitting and free of holes and tears.
  • Encouraging neighbors to help eliminate standing water on their properties.

The second important step is to prevent mosquitos from biting:

  • Use mosquito repellent when outdoors
  • Wear shoes, socks, long pants and long-sleeved shirts when outdoors for long periods of time
  • Minimize outdoor activities between dusk and dawn

“These simple measures to reduce or eliminate places where mosquitos breed on your own property will help you, your family, and your neighbors from possible serious illness,” Dr. Lohff said.

The City of Chicago’s effort against West Nile Virus is nearly year-round. From early spring through late fall, CDPH staff, other City departments and sister agencies meet regularly to assess past efforts and improve methods of disease surveillance and mosquito control. CDPH bases the decision to spray based on data collected and sprays only when there is a clear indication that human health is at risk. This year’s West Nile prevention efforts, on the same track as the successful strategy of recent years, include:

** Larviciding Catch Basins

Crews led by Vector Disease Control International are dropping larvicide briquettes down the catch basins on the public way. The slow-dissolving briquettes will, for the next five months, prevent large amounts of mosquito larvae from developing into biting adults.

Also, Chicago’s sister agencies are assisting by providing larvicide treatments for their agencies, Chicago Park District and Chicago Public Schools. The Department of Aviation has their own comprehensive program.
Larviciding works. CDPH analysis in recent years has showed a 90 percent effectiveness rate.

** Eliminating Standing Water

Using its legal authority as it relates to stagnant water that may pose a public health hazard, the City stands ready to enforce ordinances against unmaintained swimming pools and construction sites, as well as tall and overgrown weeds.

Further, City officials are once again contacting owners and managers of cemeteries, shopping centers and other properties to encourage elimination of standing water.

** Conducting Surveillance of Mosquitoes and Birds

Department of Public Health staffers trap and collect mosquitoes from throughout the city for analysis. Also, operators answering 311 calls, as well as select Streets and Sanitation staff, have been trained by CDPH to assess and respond to ”dead bird” reports from individual Chicagoans.

For an expert national perspective on West Nile Virus, visit www.cdc.gov/ncidod/dvbid/westnile/index.htm.