When West Nile virus (WNv) arrived in the Front Range in 2003, human cases reached epidemic levels in Colorado. Cases declined sharply in 2004, and although WNv is now endemic with cases occurring every year, it has not reached epidemic levels after 2003. Whenever mosquitoes are active, you should assume that West Nile virus is present and take precautions to protect yourself. Always inspect your property and drain standing water to prevent mosquito breeding near your home and within the community. The West Nile Virus Fact Sheet provides more information to keep you and your family safe.
What is the vector index and what does it mean? The vector index estimates risk to people of contracting WNv by calculating the abundance of Culex mosquitoes - the type of mosquito that can become infected with WNv - and the infection rate of WNv in mosquitoes. When the vector index reaches 0.75, the risk is considered high enough to warrant additional actions to search for any missed Culex breeding sites and to locate and drain any standing water. The city works with other agencies to coordinate information and communication.
Individuals are always advised to take protective measures to avoid mosquito bites and reduce Culex breeding on private property during every mosquito season, regardless of vector index results. As WNv risk increases, the city will increase communication and outreach to the community to provide information to keep people safe.