Additional West Nile Virus Sample Positive in Laramie


West Nile virus (WNv) has been documented for a second time this season in Laramie. The second positive sample was from mosquitoes collected from a surveillance trap monitored by City of Laramie Mosquito Control. This trap was located within the City limits. The first WNv positive was detected in an avian sample collected in the local area. The sample was determined to be positive for WNv using the City’s Rapid Analyte Measurement Platform (RAMP) analyzer on August 4th.

The rating of the Risk of West Nile virus infection continues to be rated at LEVEL 1 (LOW RISK) based on the Centers for Disease Control (CDC) guidelines for a phased response to WNv surveillance data. Currently virus activity is categorized as “Limited to sporadic activity in local mosquitoes and birds”. City of Laramie technicians have tested a total of 35 samples of Culex tarsalis mosquitoes throughout the summer season. Culex tarsalis is the known vector of WNv in the region. So far no equine or human cases have been reported at this time in Albany County. This week, Wyoming Department of Health also released notice of the first human case of WNv in the state in Goshen County. Additionally Goshen County reported 12 positive mosquito samples. Fremont County reported 3 positive mosquito samples.

Although total mosquito numbers are currently low, vector mosquitoes that can effectively transmit WNv make up a greater percentage of the mosquito population in late summer due to the overwintering and reproduction cycles of these species. Current surveillance locally shows low to moderate numbers of vector mosquitoes being collected at trap locations adjacent to the Big Laramie River and in some rural locations. Residential surveillance sites within the city limits report low vector numbers.

Mosquito control will continue to fog perimeter neighborhoods where incidence of Culex tarsalis is greater. This tactic is designed to control any older mosquitoes that have taken up harborage in areas of the City after being displaced from rural agricultural habitat by the haying harvest. A return to full residential fogging will be evaluated after Mosquito Control has completed fogging in each of the 4 zones and after trap data and subsequent RAMP testing is evaluated.

Mosquito Control is also currently performing targeted fogging operations to control vector mosquitoes in areas of higher vector densities and areas where citizens often recreate in the evening hours. Targeted areas include: Parks and recreation areas, golf courses, and the Laramie River Greenbelt Trail. All “No Spray” zones will continue to be honored at this time.

Citizens are reminded that WNV can infect people of all ages but the elderly may be at the greatest risk for a serious infection. Locally, the mosquitoes that transmit WNV are most active after dusk and citizens should limit activities in areas with high mosquito populations during this time. Repairing screens, especially in sleeping rooms, and using personal protection such as proper clothing and insect repellent containing DEET can also reduce the risk. Further Wyoming WNv information can be found on line at: the or the Centers for Disease Control website:

Hotline information regarding chemical applications on City owned properties will be updated daily at 4 pm. Call 721-5056 or click on the Mosquito and Chemical Application hotline tab on the City of Laramie home page.

For further information contact Keith Wardlaw, Mosquito Control Crew Supervisor at 721-5258 or Todd Feezer Parks and Recreation Director at 721-52604.