West Nile virus (WNV) is a mosquito-borne illness that can affect Coloradans from late spring to mid-September.  In 2012, there were 131 cases of WNV reported in Colorado, resulting in five deaths.


While most people who become infected with WNV will experience very minor symptoms, one in five people may develop fever, headache, body aches, nausea, and vomiting. These flu-like symptoms usually appear within three to 14 days of being infected and often end after a few days to several weeks.

About 1 in 150 people infected with WNV will continue to develop more severe symptoms, including high fever, headache, neck stiffness, confusion, convulsions, vision loss, paralysis, coma, and even death. Serious illness can occur in people of any age, but the elderly and those with weakened immune function are particularly at risk. Symptoms may last from several weeks to years, and effects may be permanent. If any of these symptoms occur, medical attention should be sought immediately.

What can be done to prevent West Nile virus?

Consider the 4 Ds.  It is important to DRAIN standing water whenever possible.  Mosquitoes tend to be active at DAWN and at DUSK.  Avoiding being outside during these times will decrease a person’s chance of being bitten.  If you must be out during these peak times, DRESSING appropriately (long sleeves, pants) is helpful.  Also, wearing insect repellent that contains DEET can decrease the risk of being bitten by a mosquito. Products containing DEET should not be applied to infants younger than 2 months and should be used only lightly around the eyes and mouth in all children. For infants, natural insect repellants such as citronella may be used, but the best prevention may come from dressing him in light-colored clothing that will cover as much of his skin as possible when outdoors. More information on WNV and children may be found at www.healthychildren.org.

Other things that can be done to make habitat for mosquito larvae less hospitable include removing standing water in places like ponds, ditches, gutters, flower pots, bird baths, tires and cans.  Lawns and gardens should not be overwatered. Remember, mosquitoes only need an inch of water to lay eggs, and in warm weather they can breed in as little as 10 days. Livestock water tanks and ornamental ponds may be treated with Bacillus thuringiensis israelensis (Bti), a type of bacteria that kills mosquito larvae but is safe for animals.  Local garden stores commonly carry this product.

Lastly, if you find a dead bird, do not handle it with your bare hands. Birds may also carry WNV, transmitting it to mosquitoes, and on to humans. The bird can be disposed of safely by using rubber gloves and/or a shovel, placing the bird in a plastic bag, and disposing of it in a covered outdoor trashcan with your regular trash.

Additional Information

For more information on or about WNV, go to www.FightTheBiteColorado.com or contact your local public health department.

  • Alamosa County Public Health Department:  719.589.6639
  • Conejos County Public Health and Nursing Service:  719.274.4307
  • Costilla County Public Health Agency: 719.672.3332
  • Mineral County Public Health:  719.658.2416
  • Rio Grande County Public Health Agency:  719.657.3352
  • Saguache County Public Health:  719.655.2727

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