{"id":132024,"date":"2026-06-05T13:57:25","date_gmt":"2026-06-05T19:57:25","guid":{"rendered":"https:\/\/dh.durangoherald.com\/tj\/mosquitoes-arrived-early-in-colorado-heres-what-health-officials-are-watching\/"},"modified":"2026-06-05T13:57:25","modified_gmt":"2026-06-05T19:57:25","slug":"mosquitoes-arrived-early-in-colorado-heres-what-health-officials-are-watching","status":"publish","type":"post","link":"https:\/\/dh.durangoherald.com\/tj\/mosquitoes-arrived-early-in-colorado-heres-what-health-officials-are-watching\/","title":{"rendered":"Mosquitoes arrived early in Colorado. Here\u2019s what health officials are watching"},"content":{"rendered":"

\"Spring
Spring rain, summer drought and heat created ideal conditions for mosquitoes to spread the West Nile virus throughout Colorado last year. (A. Marm Kilpatrick\/Dept. of Ecology & Evolutionary Biology, University of California-Santa Cruz)<\/span><\/figcaption><\/figure>\n<\/p>\n

The Colorado Department of Public Health and Environment says anecdotal reports of mosquitoes began surfacing as early as March, likely tied to the state\u2019s low snowfall this winter. But officials caution that doesn\u2019t necessarily mean we\u2019re headed for a worse-than-usual mosquito season.<\/p>\n

\u201cThis year, in particular, with that mild winter, warm spring, normally we would think that that would give mosquitoes a headstart on the season,\u201d said CDPHE public health entomologist Chris Roundy. \u201cBut along the Front Range in the last couple of weeks, we\u2019ve had those nice cold snaps that hopefully have pushed those early mosquito populations back.\u201d<\/p>\n

Predicting the severity of Colorado\u2019s 2026 mosquito season is difficult because the cycle depends on multiple environmental and biological factors, including the transmission of West Nile virus between birds and mosquitoes themselves, overall rainfall and temperature.<\/p>\n

\"Melody
Melody Schaaf, officer manager and lab technician for Animas Mosquito Control District, identifies mosquito larvae in 2025 under the microscope in the district\u2019s new lab. (Jerry McBride\/Durango Herald file)<\/span>Jerry McBride<\/span><\/figcaption><\/figure>\n<\/p>

\u201cIn Colorado, we just have the right combination of birds that carry the virus and mosquitoes that transmit the virus, and they have proximity to our population centers along the Front Range so we have all of the right ingredients near humans to see West Nile virus activity,\u201d Roundy said.<\/p>\n

Local birds that carry the virus include corvids, robins and jays. The species of mosquito that transmits the virus is the Culex tarsalis, a golden brown insect that becomes most active in late June through the first frost of fall.<\/p>\n

Because of the combination of these species and our landscape, Roundy said Colorado consistently sees some of the nation\u2019s highest rates of West Nile virus each year.<\/p>\n

\u201cLarimer, Weld and Boulder Counties in particular are where we see a lot of both mosquito activity and West Nile virus activity,\u201d he said.<\/p>\n

Mosquitoes carrying West Nile virus were first identified in Colorado in 2003. That year resulted in the most human cases of West Nile in state history, with 2,948. Sixty-six people died.<\/p>\n

The state also saw a significant number of cases in 2023 with 634 cases identified, resulting in 51 deaths. That year, the state had an above-average snow pack and the extra moisture was followed by record precipitation in May and June.<\/p>\n

\u201cWhile year to year, we don\u2019t see a clear trend of increasing activity, severe weather patterns change every season and make us adapt to what the mosquito population looks like,\u201d Roundy said.<\/p>\n

Peak mosquito and West Nile activity in Colorado typically occurs between July and August as the summer warms up, then drops off in September when nighttime temperatures start to plummet.<\/p>\n

West Nile isn\u2019t the only mosquito risk this year<\/p>\n

This year, state health officials are also expanding surveillance for another mosquito-borne illness: St. Louis encephalitis virus.<\/p>\n

The virus, which is closely related to West Nile, was detected last year in mosquitoes in Larimer, Weld and La Plata counties.<\/p>\n

\u201cThis virus used to be really common in the U.S., but since 2000, we haven\u2019t seen much of it, so this virus has actually been reemerging,\u201d Roundy said. Symptoms are very similar to those of West Nile, including fever and chills, fatigue and headache.<\/p>\n

Health officials are also continuing to monitor the spread of Aedes aegypti, an invasive mosquito species capable of carrying viruses including dengue and Zika. The species has established itself in the Grand Junction area, though officials say the current public health risk remains low.<\/p>\n

\u201cThankfully, presence of the mosquito does not mean that we have those viruses automatically,\u201d Roundy said. \u201cIt would take an infected traveler returning to Colorado, being bitten by one of those mosquitoes for local transmission to be a concern.\u201d<\/p>\n

For now, health officials urge Coloradans to prepare for mosquito season by remembering The Four Ds:<\/p>\n

The Four Ds:<\/p>\n

Defend with EPA-approved repellents (e.g., DEET, picaridin).<\/list-item>Dress in long sleeves\/pants.<\/list-item>Drain standing water around homes.<\/list-item>Dusk\/Dawn \u2013 avoid outdoor activity during these peak mosquito hours.<\/list-item><\/div>\n

To read more stories from Colorado Public Radio, visit www.cpr.org.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

Surveillance being expanded for St. Louis encephalitis virus, closely related to West Nile<\/p>\n","protected":false},"author":1,"featured_media":132025,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[5736,5735],"tags":[28,61],"naviga_topic":[],"class_list":["post-132024","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-local-news","category-news","tag-headlines","tag-health"],"acf":[],"author_name":"dh_admin","_links":{"self":[{"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/posts\/132024","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/comments?post=132024"}],"version-history":[{"count":0,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/posts\/132024\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/media\/132025"}],"wp:attachment":[{"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/media?parent=132024"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/categories?post=132024"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/tags?post=132024"},{"taxonomy":"naviga_topic","embeddable":true,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/naviga_topic?post=132024"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}