Colorado’s first human cases of West Nile virus in 2025 confirmed in Adams County

Colorado’s first human cases of West Nile virus this year were confirmed in two people who contracted the disease in Adams County, public health officials said Thursday. Those individuals likely contracted the virus from infected mosquitoes in late June, the Adams County Health Department said in a news release. While no mosquitoes have tested positive for West Nile in Adams County, neighboring counties have confirmed the virus’s presence. Colorado’s West Nile season started early this year, with mosquitoes testing positive for the virus in Denver, Boulder County and Weld County near Greeley and Johnstown earlier this month. While West Nile can be fatal in rare cases, most people don’t show signs of infection. About 20% of people develop flu-like symptoms and fewer than 1% develop a serious, potentially deadly illness, Adams County officials said. Related Articles Weld County mosquitoes test positive for West Nile virus Denver confirms presence of West Nile virus as season starts early along Front Range People 60 years and older and with certain medical conditions are at a higher risk for serious illness, and anyone who develops a severe headache or becomes confused should see their health care provider. The best way to prevent West Nile is to protect against mosquito bites. People can take precautions like using insect repellent, limiting time outdoors at dawn and dusk and wearing long-sleeved shirts and pants when near mosquitoes, Adams County officials said. Mosquitoes breed in standing water, so emptying water from birdbaths, rain barrels, toys and flower pots at least once a week can also help limit the spread. The Adams County Health Department is distributing free insect repellent at its Westminster clinic, 1401 W. 122nd Ave., and at community outreach events throughout the summer. Sign up for our weekly newsletter to get health news sent straight to your inbox.