The first cases of WNV disease appeared in Colorado in 2002. The initial large outbreak in 2003 was followed by a smaller one in 2007. Since 2008 annual case numbers have been lower.

Based on data from the Colorado Dept. of Public Health and Environment

Case numbers in the future are difficult to predict but there is a clear risk of future epidemics and we need to develop improved capacity both for early detection of elevated WNV activity and for effective vector control response.

Winters, Pape, Moore and Eisen; unpublished data

Outcome of exposure to West Nile virus:

Information from the Colorado Dept. of Public Health and Environment West Nile virus webpage:
http://www.cdphe.state.co.us/dc/Zoonosis/wnv/westnilefaq.html

• Most people who are infected with West Nile virus do not become ill and have no symptoms.
  
• For persons who do become ill, the time between the mosquito bite and the onset of symptoms, known as the incubation period, ranges from 5-15 days
• Two clinically different types of disease occur in humans: (1) viral fever syndrome, and (2) encephalitis, an inflammation of the brain
• Symptoms of the viral fever syndrome include fever, headache, and malaise. These symptoms persist for about 2-7 days
• In rare cases, the virus can cause a more serious brain infection such as aseptic meningitis or encephalitis. These infections begin with a sudden onset of high fever and a headache, and then may progress to stiff neck, disorientation, tremors, and coma. Severe infections can result in permanent brain damage or death. Most deaths occur in persons over 50 years of age
• There is no vaccine for use in humans against West Nile virus and no specific treatment for infection except supportive care.

To decrease risk of exposure to vector mosquitoes and West Nile virus:

Information from the Colorado Dept. of Public Health and Environment West Nile virus webpage:
http://www.cdphe.state.co.us/dc/Zoonosis/wnv/westnilefaq.html

• Limit outside activity around dawn and dusk when Culex tarsalis vector mosquitoes feed.
  This is particularly important for elderly adults and small children.
• Wear protective clothing such as lightweight long pants and long sleeve shirts when outside.
• Apply insect repellant to exposed skin when outside. Repellents with DEET are effective, but should be applied sparingly. Products with 10% or less of DEET are recommended for children.
• Make sure that doors and windows have tight- fitting screens. Repair or replace screens that have tears or holes in them.

We recommend CDC's webpage for information regarding choice and safe use of mosquito repellents:
http://www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm