{"id":71588,"date":"2026-06-03T08:46:22","date_gmt":"2026-06-03T14:46:22","guid":{"rendered":"https:\/\/www.uchealth.org\/today\/?p=71588"},"modified":"2026-06-05T15:21:48","modified_gmt":"2026-06-05T21:21:48","slug":"west-nile-virus-in-colorado","status":"publish","type":"post","link":"https:\/\/www.uchealth.org\/today\/west-nile-virus-in-colorado\/","title":{"rendered":"Colorado sees first West Nile case of 2026: What to know about mosquitoes and this dangerous illness"},"content":{"rendered":"<div style=\"margin-top: 0px; margin-bottom: 0px;\" class=\"sharethis-inline-share-buttons\" ><\/div><figure id=\"attachment_71521\" aria-describedby=\"caption-attachment-71521\" style=\"width: 640px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-71521\" src=\"https:\/\/uchealth-wp-uploads.s3.amazonaws.com\/wp-content\/uploads\/sites\/6\/2023\/08\/29091915\/Getty-man-putting-on-bug-spray-web.webp\" alt=\"Colorado health officials have reported the first death of 2025 from the dangerous mosquito-borne illness, West Nile virus. Last summer, Colorado was among the top five states in the U.S. for cases of West Nile virus. And in 2023, 50 people died in Colorado from West Nile virus, marking the worst outbreak in the U.S. that year. Photo: Getty Images.\" width=\"640\" height=\"426\" \/><figcaption id=\"caption-attachment-71521\" class=\"wp-caption-text\">Colorado health officials have reported the first human case of the dangerous mosquito-borne illness, West Nile virus, this year. In 2025, Colorado was the top state in the U.S. for cases of West Nile virus, and in 2023, 50 people died in Colorado from West Nile virus, marking the worst outbreak in the U.S. that year. Photo: Getty Images.<\/figcaption><\/figure>\n<p>A patient in Jefferson County, west of Denver, has become the first person this year in Colorado with a confirmed case of West Nile virus, a dangerous mosquito-borne illness<span data-olk-copy-source=\"MessageBody\">.<\/span><\/p>\n<p>Infected mosquitoes spread West Nile virus by biting us. Most people who get the virus do not feel sick, or they might have mild symptoms such as fever, headache, body aches or fatigue. In rare case, the virus can cause scary neurological impairments and swelling in the brain in those who get a severe case.<\/p>\n<p>Public health officials stress the importance of using mosquito repellent and draining standing water to prevent West Nile virus infections. Jefferson County officials noted that even in areas affected by Colorado&#8217;s drought conditions this year, mosquitoes can breed in standing water.<\/p>\n<p>&#8220;Dry weather doesn\u2019t mean mosquitoes aren\u2019t around,&#8221; said James Rada, Jefferson County environmental health director. &#8220;We want to make sure everyone can get the most out of the time we get to spend outside in the summer months by keeping the risk of mosquito bites as low as possible.&#8221;<\/p>\n<div class=\"su-callout-box col-xs-12 col-sm-6 right\" style=\"background-color:#dce4e7; color:#2e3b44;\">\n<h4><strong>How to avoid getting West Nile virus<\/strong><\/h4>\n<ul>\n<li style=\"font-weight: 400\"><span style=\"font-weight: 400\">Wear long sleeves and long pants when you\u2019re outdoors.<\/span><\/li>\n<li style=\"font-weight: 400\"><span style=\"font-weight: 400\">Be especially wary of mosquitoes in the mornings and evenings when they\u2019re most active.<\/span><\/li>\n<li style=\"font-weight: 400\"><span style=\"font-weight: 400\">Avoid areas near standing water where mosquitoes breed.<\/span><\/li>\n<li style=\"font-weight: 400\"><span style=\"font-weight: 400\">Parents can get mosquito netting to cover babies in strollers.<\/span><\/li>\n<li style=\"font-weight: 400\"><span style=\"font-weight: 400\">Use highly effective insect repellents that contain one of the following ingredients: DEET; Picaridin (known as KBR 3023 and icaridin outside the U.S.); IR3535; Oil of lemon eucalyptus (OLE); Para-menthane-diol (PMD); 2-undecanone. Find the right insect repellent for you by using <\/span><span style=\"font-weight: 400\"><a id=\"\" href=\"https:\/\/www.epa.gov\/insect-repellents\/find-repellent-right-you\">EPA\u2019s search tool<\/a>. (Some repellents are not appropriate for babies and children.)<\/span><\/li>\n<li style=\"font-weight: 400\"><span style=\"font-weight: 400\">If you are also using sunscreen, apply sunscreen first and insect repellent second.<\/span><\/li>\n<\/ul>\n<\/div>\n<p dir=\"ltr\">So far this year, <a id=\"\" href=\"https:\/\/www.cdc.gov\/west-nile-virus\/data-maps\/current-year-data.html\" target=\"_blank\" rel=\"noopener\">13 cases of human West Nile virus have been reported in the U.S<\/a>., not including the Colorado case, according to data from the U.S. Centers for Disease Control and Prevention.<\/p>\n<p dir=\"ltr\">Last year, <a id=\"\" href=\"https:\/\/cdphe.colorado.gov\/animal-related-diseases\/west-nile-virus\/west-nile-virus-data\" target=\"_blank\" rel=\"noopener\">Colorado recorded 286 cases of West Nile virus,<\/a> and 20 people died, according to medical experts at the Colorado Department of Public Health and Environment. Nationally, there were about 1,900 cases of West Nile virus in 2025.<\/p>\n<p dir=\"ltr\">Colorado had 76 cases in 2024, and in 2023, Colorado experienced one of the deadliest years for West Nile since the mosquito-borne illness arrived in the U.S. in 1999. Throughout 2023, <a id=\"\" href=\"https:\/\/cdphe.colorado.gov\/animal-related-diseases\/west-nile-virus\/west-nile-virus-data\" target=\"_blank\" rel=\"noopener\">50 people<\/a> who contracted West Nile virus died in Colorado, and scores of others needed to be hospitalized.<\/p>\n<p>West Nile virus can strike healthy people of all ages. (Read about <a href=\"https:\/\/www.uchealth.org\/today\/man-with-compromised-immune-system-faced-battle-with-west-nile-virus\/\">an award-winning photographer and producer<\/a> who contracted West Nile virus in 2023 and <a href=\"https:\/\/www.uchealth.org\/today\/west-nile-virus-still-a-threat-to-colorado-how-to-know-if-you-have-west-nile\/\">a young woman who endured a tough recovery<\/a> after a bad West Nile infection in 2022.)<\/p>\n<p>Dr. Michelle Barron, <a href=\"https:\/\/www.uchealth.org\/provider\/michelle-barron-md-infectious-disease\/\">senior medical director of infection prevention and control for UCHealth<\/a>, has two key messages for people who are spending time outdoors now and for those who may be feeling sick.<\/p>\n<p>Protect yourself to avoid getting mosquito bites. And, if you are feeling sick and suspect you might have West Nile virus, seek help from a doctor immediately.<\/p>\n<p>\u201cIf your infection progresses to the point where you are having persistent headaches, confusion, any kind of muscle weakness, numbness or tingling, you need to be seen by a doctor as quickly as possible,\u201d Barron said.<\/p>\n<p>To understand more about West Nile virus and to prevent people from getting sick, we asked Barron some of your top questions about West Nile virus.<\/p>\n<p>Along with her work for UCHealth, Barron is a\u00a0<a id=\"\" href=\"https:\/\/som.ucdenver.edu\/Profiles\/Faculty\/Profile\/8603\" target=\"_blank\" rel=\"noopener\">professor of medicine and infectious diseases<\/a>\u00a0at the\u00a0<a id=\"\" href=\"https:\/\/medschool.cuanschutz.edu\/\" target=\"_blank\" rel=\"noopener\">University of Colorado Anschutz School of Medicine<\/a>\u00a0and is one of the <a id=\"\" href=\"https:\/\/www.uchealth.org\/today\/meet-the-top-infectious-disease-expert-in-colorado\/\" target=\"_blank\" rel=\"noopener\">top infectious disease experts<\/a> in the Rocky Mountain region.<\/p>\n<figure id=\"attachment_71572\" aria-describedby=\"caption-attachment-71572\" style=\"width: 600px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-71572\" src=\"https:\/\/uchealth-wp-uploads.s3.amazonaws.com\/wp-content\/uploads\/sites\/6\/2023\/08\/31123629\/Dr.-Barron-seated-portrait-tiny.webp\" alt=\"Dr. Michelle Barron is one of the top infectious disease experts in the Rocky Mountain Region. Photo by Sonya Doctorian.\" width=\"600\" height=\"405\" \/><figcaption id=\"caption-attachment-71572\" class=\"wp-caption-text\">Dr. Michelle Barron is one of the top infectious disease experts in the Rocky Mountain Region. She&#8217;s urging people to be on guard against West Nile virus, which can be deadly. Photo by Sonya Doctorian, UCHealth.<\/figcaption><\/figure>\n<h2><strong>What is West Nile virus?<\/strong><\/h2>\n<p>West Nile virus is a mosquito-borne illness that\u2019s known as a \u201cflavivirus.\u201d It was first detected in 1937 in Uganda. There were several large <a id=\"\" href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC3111838\/\" target=\"_blank\" rel=\"noopener\">outbreaks in Egypt and the Nile River Delta<\/a> in the 1950s, which is how the illness got its name. The first case in the U.S. was detected in 1999. It has since spread throughout the U.S. But <a id=\"\" href=\"https:\/\/www.cdc.gov\/west-nile-virus\/data-maps\/historic-data.html\" target=\"_blank\" rel=\"noopener\">Coloradans get a disproportionately high number of West Nile virus infections<\/a> compared to people in other larger, more populated states. So, people living in Colorado and other states where West Nile virus infections are more common need to be especially vigilant about preventing mosquito bites.<\/p>\n<p>Mosquitoes can pick up the virus from birds and other animals and then spread it to people when they bite us.<\/p>\n<h2><strong>What is the typical season for West Nile virus cases in Colorado?<\/strong><\/h2>\n<p>The season usually lasts from June through September, but if we have a mild, wet fall, mosquitoes may continue to circulate later in the fall, and thus, they could continue to infect people.<\/p>\n<h2><strong>Is West Nile virus also bad elsewhere in the U.S.?\u00a0<\/strong><\/h2>\n<p>It&#8217;s too soon to know how dangerous West Nile virus will be both in Colorado and across the U.S. this year. It takes time for state health officials to record cases of West Nile virus, and many people who get sick with West Nile virus don&#8217;t know they have it and thus, never report their illness to health officials.<\/p>\n<h2><strong>Was 2023 one of the worst years on record for West Nile virus in Colorado?<\/strong><\/h2>\n<p>Yes. Colorado has had bad years for West Nile virus in recent years. In 2023, 50 people who contracted West Nile virus died in Colorado. In 2022, there were 20 deaths, and in 2021, there were 11 deaths, <a id=\"\" href=\"https:\/\/cdphe.colorado.gov\/animal-related-diseases\/west-nile-virus\/west-nile-virus-data\" target=\"_blank\" rel=\"noopener\">according to the Colorado Department of Public Health and Environment.<\/a><\/p>\n<p>The worst year on record in Colorado was soon after the West Nile virus arrived in the state. In 2003, 66 people died after becoming infected with the virus.<\/p>\n<h2><strong>What are the common symptoms of West Nile virus?<\/strong><\/h2>\n<p>The key symptoms of West Nile virus include:<\/p>\n<ul>\n<li>Headache<\/li>\n<li>Fever<\/li>\n<li>Diarrhea<\/li>\n<li>Muscle weakness<\/li>\n<li>Tingling or numbness<\/li>\n<li>Neck stiffness<\/li>\n<li>Flu-like symptoms<\/li>\n<\/ul>\n<p>\u201cMost people will have minor symptoms and may not ever know that they had West Nile virus,\u201d Barron said.<\/p>\n<h2><strong>Do some people get rashes when they get West Nile virus?<\/strong><\/h2>\n<p>Rashes are not common with West Nile virus, but it&#8217;s possible to get one. If you are not feeling well and have questions about symptoms, reach out to your doctor.<\/p>\n<h2><strong>People with severe cases of West Nile virus can develop neurological symptoms. How would you know that you are having these kinds of issues?<\/strong><\/h2>\n<p>The neurologic symptoms related to West Nile virus can include the following:<\/p>\n<ul>\n<li>Clumsiness<\/li>\n<li>Problems walking<\/li>\n<li>Brain fog or cognitive problems<\/li>\n<li>Memory issues<\/li>\n<\/ul>\n<p>When a case of West Nile virus becomes severe, Barron said patients can suffer from critical problems like encephalitis, which is inflammation of the brain, and meningitis, which is swelling in the lining of the brain and the spinal cord.<\/p>\n<p>\u201cPeople sometimes will start acting strange. They\u2019ll have cognitive issues. They might have trouble with word finding. They might be a little slower or will have some weaknesses develop. Walking can be a challenge,\u201d Barron said.<\/p>\n<p>\u201cThey can have a polio-like syndrome where they can\u2019t walk and have paralysis,\u201d Barron said.<\/p>\n<p>Her advice for anyone having these types of neurologic symptoms is utterly clear: Seek help immediately.<\/p>\n<h2><strong>Is there a test for West Nile virus?<\/strong><\/h2>\n<p>Yes. If you are sick and suspect that you might have West Nile virus, see your medical provider so they can arrange for you to be tested for West Nile virus.<\/p>\n<h2><strong>Are there any cures for West Nile virus?<\/strong><\/h2>\n<p>No. Despite decades of research and efforts to come up with a cure, there\u2019s no cure yet for West Nile virus. In the past, Barron said, doctors experimented with using antibodies from previously infected people in patients with new infections. Unfortunately, clinical trials showed that those therapies were not effective.<\/p>\n<p>While there are no cures for West Nile virus, doctors can help with other symptoms, like reducing a patient\u2019s fever or providing supportive care if they have swelling in the brain.<\/p>\n<p>\u201cIf you\u2019re having neurological symptoms, you want to make sure you see a doctor because the symptoms can get worse,\u201d Barron said.<\/p>\n<p>There\u2019s no way to reverse the virus, but doctors can provide help.<\/p>\n<p>\u201cIf you\u2019re having trouble breathing, we can monitor that. If you\u2019re having fevers, we can control that. If you\u2019re having weakness, we can work on rehabilitation,\u201d she said.<\/p>\n<h2><strong>Is there a vaccine to prevent West Nile virus?<\/strong><\/h2>\n<p>No. As with cures, researchers have been working for years to create a vaccine for humans to prevent West Nile virus. Unfortunately, there is not a vaccine yet. But there is <a id=\"\" href=\"https:\/\/aaep.org\/guidelines\/vaccination-guidelines\/core-vaccination-guidelines\/west-nile-virus\" target=\"_blank\" rel=\"noopener\">a vaccine to prevent West Nile virus in horses<\/a>, so it\u2019s possible that vaccines for humans could come soon.<\/p>\n<h2><strong>What if I had West Nile virus in the past? Could I get it again, or would I still have immunity to fight another infection?<\/strong><\/h2>\n<p>Researchers and doctors are still learning about West Nile virus, but they think that once a person has West Nile virus, they should have lifelong immunity to the virus.<\/p>\n<h2><strong>What can I do to avoid getting West Nile virus?<\/strong><\/h2>\n<p>West Nile virus is highly preventable, but if you like being outside, it\u2019s not easy to avoid mosquitoes.<\/p>\n<p>Here are some ideas for staying safe:<\/p>\n<ul>\n<li>If you\u2019re spending time outdoors, consider wearing long sleeves and long pants, so it\u2019s not easy for mosquitoes to bite you.<\/li>\n<li>Use a highly effective insect repellent, preferably one containing DEET.<\/li>\n<\/ul>\n<p>\u201cIf you\u2019re out hiking or even if you\u2019re out sitting on your deck or your patio, it\u2019s a good idea to protect yourself. You can use insect repellent, citronella candles or anything that helps keep the mosquitoes down,\u201d Barron said. \u201cAnd make sure there\u2019s no standing water where mosquitoes can breed.\u201d<\/p>\n<h2><strong>Are there certain times of day when you should be more cautious?<\/strong><\/h2>\n<p>Yes. Mosquitoes are especially active at dawn and dusk.<\/p>\n<p>\u201cAvoiding being outside at those times may help you avoid West Nile virus,\u201d Barron said.<\/p>\n<p>Overall, her advice is to prevent bites. Be prepared and pay attention.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>A patient in Jefferson County, west of Denver, has become the first person this year in Colorado with a confirmed case of West Nile virus, a dangerous mosquito-borne illness. Infected mosquitoes spread West Nile virus by biting us. Most people who get the virus do not feel sick, or they might have mild symptoms such [&hellip;]<\/p>\n","protected":false},"author":2123,"featured_media":71521,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_relevanssi_hide_post":"","_relevanssi_hide_content":"","_relevanssi_pin_for_all":"","_relevanssi_pin_keywords":"","_relevanssi_unpin_keywords":"","_relevanssi_related_keywords":"","_relevanssi_related_include_ids":"","_relevanssi_related_exclude_ids":"","_relevanssi_related_no_append":"","_relevanssi_related_not_related":"","_relevanssi_related_posts":"","_relevanssi_noindex_reason":"","footnotes":""},"categories":[6,8],"tags":[392,162],"class_list":["post-71588","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-healthy-living","category-news","tag-infection-prevention","tag-infectious-diseases"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v27.7 (Yoast SEO v27.7) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>West Nile virus case reported in Colorado: Mosquito risks in 2026 - UCHealth Today<\/title>\n<meta name=\"description\" content=\"West Nile virus caused ## deaths in Colorado in 2025. 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Learn about health risks.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.uchealth.org\/today\/west-nile-virus-in-colorado\/\" \/>\n<meta property=\"og:site_name\" content=\"UCHealth Today\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/uchealthorg\/\" \/>\n<meta property=\"article:published_time\" content=\"2026-06-03T14:46:22+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-06-05T21:21:48+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/uchealth-wp-uploads.s3.amazonaws.com\/wp-content\/uploads\/sites\/6\/2023\/08\/29091915\/Getty-man-putting-on-bug-spray-web.jpg\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"Katie Kerwin McCrimmon, UCHealth\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@uchealth\" \/>\n<meta name=\"twitter:site\" content=\"@uchealth\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Katie Kerwin McCrimmon, UCHealth\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"9 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/www.uchealth.org\\\/today\\\/west-nile-virus-in-colorado\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.uchealth.org\\\/today\\\/west-nile-virus-in-colorado\\\/\"},\"author\":{\"name\":\"Katie Kerwin McCrimmon, UCHealth\",\"@id\":\"https:\\\/\\\/www.uchealth.org\\\/today\\\/#\\\/schema\\\/person\\\/d43cd81d6f8e440a3e496f8a012c68e9\"},\"headline\":\"Colorado sees first West Nile case of 2026: What to know about mosquitoes and this dangerous illness\",\"datePublished\":\"2026-06-03T14:46:22+00:00\",\"dateModified\":\"2026-06-05T21:21:48+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/www.uchealth.org\\\/today\\\/west-nile-virus-in-colorado\\\/\"},\"wordCount\":1819,\"publisher\":{\"@id\":\"https:\\\/\\\/www.uchealth.org\\\/today\\\/#organization\"},\"image\":{\"@id\":\"https:\\\/\\\/www.uchealth.org\\\/today\\\/west-nile-virus-in-colorado\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/uchealth-wp-uploads.s3.amazonaws.com\\\/wp-content\\\/uploads\\\/sites\\\/6\\\/2023\\\/08\\\/29091915\\\/Getty-man-putting-on-bug-spray-web.webp\",\"keywords\":[\"Infection prevention\",\"Infectious diseases\"],\"articleSection\":[\"Healthy living\",\"News\"],\"inLanguage\":\"en-US\"},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.uchealth.org\\\/today\\\/west-nile-virus-in-colorado\\\/\",\"url\":\"https:\\\/\\\/www.uchealth.org\\\/today\\\/west-nile-virus-in-colorado\\\/\",\"name\":\"West Nile virus case reported in Colorado: Mosquito risks in 2026 - UCHealth Today\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.uchealth.org\\\/today\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/www.uchealth.org\\\/today\\\/west-nile-virus-in-colorado\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/www.uchealth.org\\\/today\\\/west-nile-virus-in-colorado\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/uchealth-wp-uploads.s3.amazonaws.com\\\/wp-content\\\/uploads\\\/sites\\\/6\\\/2023\\\/08\\\/29091915\\\/Getty-man-putting-on-bug-spray-web.webp\",\"datePublished\":\"2026-06-03T14:46:22+00:00\",\"dateModified\":\"2026-06-05T21:21:48+00:00\",\"description\":\"West Nile virus caused ## deaths in Colorado in 2025. 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