How to Stay Safe From West Nile Virus

August 27, 2012

Officials say the virus is striking people earlier this year because the weather created good breeding conditions for the mosquito that carries the virus.

Joining ABC7 Chicago was Dr. Emily Landon Mawdsley with University of Chicago Hospitals. She helped us recognize the symptoms and learn what to do to protect yourself and your family from exposure to the disease.


- Mild cases of West Nile infection symptoms: slight fever or headache.
-More severe infection symptoms: rapid onset of a high fever with head and body aches, disorientation, tremors, convulsions and, in the most severe cases, paralysis or death.
-Usually symptoms occur from three to 14 days after the bite of an infected mosquito.

Precautions include practicing the three "R's" - reduce, repel and report.

REDUCE exposure - avoid being outdoors when mosquitoes are most active, especially between dusk and dawn.Make sure doors and windows have tight-fitting screens. Repair or replace screens that have tears or other openings. Try to keep doors and windows shut, especially at night.Eliminate all sources of standing water where mosquitoes can breed, including water in bird baths, ponds, flowerpots, wading pools, old tires and any other receptacles.

REPEL - when outdoors, wear shoes and socks, long pants and a long-sleeved shirt, and apply insect repellent that contains DEET, picaridin, oil of lemon eucalyptus or IR 3535, according to label instructions. Consult a physician before using repellents on infants.

REPORT - In communities where there are organized mosquito control programs, contact your municipal government to report dead birds and areas of stagnant water in roadside ditches, flooded yards and similar locations that may produce mosquitoes.

Additional information about West Nile virus can be found on the Illinois Department of Public Health's website at


1. History: West nile virus is a flavivirus that is related to dengue fever, yellow fever, and st louis encephalitis virus. It was first identified in Uganda in 1937. An important outbreak in Isreal in 1957 established its place as a cause of neurologic infection. Since then, the disease has spread to much of the world. The first US cases occurred in 1999 in New York City and quickly spread to 47 states and Canada.

2. WNV is transferred back and forth between mosquitos and birds. Many birds, robins especially, can carry the disease long term without dying resulting in transmission to the mosquito population each summer. This, in turn, leads to more infected birds (the "reservoir" of infection) and by late summer a critical mass of birds and mosquitos are infected resulting in accidental transmission of the virus to humans. As the evenings get cooler, mosquitos begin to die off and human infections decrease.

3. 80 percent of people infected with WNV will have no symptoms at all. 20% will develop "West Nile Fever" about 3-14 days after being bitten which is characterized by fever, chills, muscle aches, headache, and sometimes a rash or even weakness. This illness usually lasts about a week but some people feel sick for much longer (up to a month). Only 1 in 150 people get severe neurologic disease like encephalitis (brain swelling) or meningitis (infection of the brain's covering membrane). These people usually start with a fever and mild symptoms but worsen rather quickly with severe headache, confusion, severe sleepiness (decreased consciousness), neck stiffness, muscle weakness or twitching and sometimes paralysis.

4. There is no treatment for WNV infection but patients with neurologic symptoms usually need supportive care in a hospital, often in an intensive care unit while they go through the illness. Many people survive encephalitis but they often have persistent weakness or muscular problems.

5. Mild disease usually goes undiagnosed but sometimes is found on blood tests specifically ordered to look for WNV. Neurologic disease is usually diagnosed by sampling the spinal fluid (lumbar puncture or spinal tap).

6. People over the age of 50 are at higher risk than younger people, as are infants and those with chronic medical conditions like diabetes or depressed immune systems. 50 year olds don't usually consider themselves old enough to be at high risk for serious infections but it's important to recognize that this is one time where they need to be extra careful. There is no human-to-human transmission excepting from blood transfusion or organ transplantation but blood and tissues are routinely tested for WNV prior to being used.

7. There is no human vaccine available so prevention methods focus on avoiding mosquito bites. WNV is transmitted by night biting mosquitos so the highest risk times are between dusk and dawn. Having tight fitting window screens is also important. Keeping arms and legs covered and using a mosquito repellent with DEET is effective if you must be outside. Clearing up any stagnant water (bird baths, tire swings, drainage ditches) will also help decrease mosquito populations.

8. This year we have seen more cases in the US than usual and many scientists estimate that this could be the worst year ever. That said, almost half of the cases are in Texas and the health departments in the south have been doing a lot to prevent transmission. As of 8/21, there have been 21 total cases reported in IL with only 1 death confirmed. We have seen 1 or 2 cases at UCM and we routinely look for this infection every summer. The department of public health actively checks mosquito pools for presence of the virus and treats those pools if positive. The number of positive pools decreased over the last two weeks which is a good sign.

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