Colorado Warns 2026 Tick Season Will Surge, Raising Risk of 4 Rare Illnesses

Q: As ticks expand their territory, what new diseases might be the next to arrive in Colorado?

The most likely new threats for Colorado are Lyme disease and illnesses linked to the lone star tick, especially alpha-gal syndrome and ehrlichiosis. Right now, Colorado’s native ticks mainly spread Colorado tick fever, Rocky Mountain spotted fever, tularemia and related illnesses. But experts say warming temperatures and shifting habitats are helping other tick species move into new territory. The blacklegged tick, which carries Lyme disease, is expanding in the U.S., making Lyme the clearest long-term concern if that tick becomes established in Colorado. At present, Colorado’s reported Lyme cases are tied to travel, not local transmission. The other major watch item is the lone star tick, which has been moving north and west and is nearing Colorado’s eastern border. If it gains a foothold, it could bring alpha-gal syndrome, the red-meat allergy triggered by tick bites, along with ehrlichiosis. It is also associated with Southern tick-associated rash illness, and more rarely Heartland virus and Bourbon virus. Some of these risks are still emerging rather than established. State and university experts stress that surveillance matters because disease arrival depends on whether the tick species themselves can survive and reproduce in Colorado. That is why Colorado is urging residents to submit ticks through its “tick spy” program and why doctors are being told to consider tick exposure when patients develop fever, rash or other compatible symptoms after time outdoors.

Q: A tick bite can now trigger a lifelong meat allergy. Which Colorado areas are most at risk?

No Colorado area is currently identified as a clear hotspot for the tick bite that can trigger alpha-gal syndrome, the red-meat allergy. State experts say the main tick linked to alpha-gal, the lone star tick, is not established in Colorado. The risk to watch is along Colorado’s eastern edge. Chris Roundy of the Colorado Department of Public Health and Environment said the lone star tick is expanding westward and is getting closer to Colorado’s eastern border. That means if any part of the state becomes more vulnerable, the eastern plains would be the most likely place to watch. By contrast, the ticks commonly found in Colorado now are the American dog tick, mainly along the Front Range and eastern plains, and the Rocky Mountain wood tick, common in mountain and western areas. Those species can spread other illnesses, including Rocky Mountain spotted fever and Colorado tick fever, but they are not the main driver of alpha-gal syndrome. So for now, Colorado’s broader tick danger is real statewide, especially in grassy, brushy, and rural areas, but the specific lifelong meat-allergy risk remains more of an emerging concern than a current established threat inside the state. People traveling to states where lone star ticks are common face a clearer alpha-gal risk than most people staying within Colorado.

3 articles · Updated · The Colorado Sun · Jun 12

Colorado health officials expect an unusually heavy 2026 tick season after a mild winter and warm spring boosted tick survival and sped up host-seeking.
A wet 2023 spring also still matters: taller grasses improved habitat, more eggs were laid, and ticks’ multi-year life cycle has kept that population boom going.
Two main species dominate the state — American dog ticks on the Front Range and eastern plains, Rocky Mountain wood ticks in the mountains and west — carrying risks including Rocky Mountain spotted fever and Colorado tick fever.
Reported illness remains rare, with 2025 totals of two Colorado tick fever cases, six Rocky Mountain spotted fever cases, two tick-borne relapsing fever cases and nine tularemia cases of unclear origin.
Lyme disease is not established in Colorado because deer ticks do not live there, but Coloradans still logged 47 cases last year after travel to other states.