**Plague (Yersinia pestis) remains endemic in rural areas of the western U.S., primarily New Mexico and Arizona, where it circulates among rodents and fleas, producing an average of about seven human cases annually.** Official CDC surveillance data show only two confirmed U.S. cases in 2026 through late September—one each in Arizona and New Mexico—consistent with the long-term baseline and well below historical peaks of 17. Most cases cluster from late spring through early fall, aligning with peak flea activity and outdoor exposure; incidence drops sharply in late fall and winter as cooler temperatures reduce vector activity. With October already underway and no reports of unusual rodent die-offs, elevated surveillance signals, or expanding geographic spread from public health agencies, the probability of an additional case materializing before year-end remains low. Recent developments, including a fatal New Mexico case in June and an unrelated suspected laboratory-associated case in Russia, have not altered U.S. transmission dynamics or prompted revised risk assessments. Traders appear to weigh these seasonal and epidemiological patterns heavily, producing the current 84% market-implied probability for no further cases by December 31.