Active Public Health Outbreaks in Montana
Surveillance Report • November 30, 2025
Critical Alert
Measles
Active outbreak across multiple counties. First resurgence in 35 years.
Epidemic Level
Syphilis
Cases at a 60-year high. 1,800% rise in congenital cases since 2020.
Seasonal Watch
Respiratory
2025-2026 season underway. Flu activity increasing statewide.
Measles Resurgence (2025)
As of late November 2025, Montana is grappling with its first significant measles outbreak in over three decades. Following the confirmation of the first cases in April 2025, the virus has spread to multiple jurisdictions. The CDC currently estimates between 10 and 49 confirmed cases in the state, part of a wider national resurgence that has seen nearly 1,800 cases across the United States this year.
The outbreak, initially centered in Gallatin County, has since expanded. Public health officials have confirmed cases in Hill, Flathead, Cascade, Yellowstone, and Lewis & Clark counties. The primary drivers identified are international travel and pockets of unvaccinated populations.
Confirmed Impact Zones (2025)
Syphilis & Congenital Syphilis
Montana is currently experiencing a syphilis epidemic of historic proportions, with case rates reaching levels not seen since 1959. Data from the Department of Public Health and Human Services (DPHHS) indicates a 728% increase in total cases between 2020 and 2023, a trend that has continued accelerating through 2024 and 2025.
Most concerning is the demographic shift; while historically prevalent in men, women of reproductive age now account for nearly 50% of new cases. This has led to a tragic spike in congenital syphilis (transmission from mother to child), which rose by 1,800% in just three years.
Congenital Syphilis Spike (2020-2023)
*Data represents confirmed congenital cases. 2024-2025 data remains provisional but indicates continued elevation.
Respiratory Virus Surveillance (2025-2026 Season)
The 2025-2026 respiratory virus season is officially underway. Early surveillance data from November 2025 shows laboratory-confirmed cases of influenza rising, though overall activity remains low compared to the peak expected in January/February.
Health officials are urging vaccination, citing the severity of the previous 2024-2025 season, which resulted in over 15,600 flu cases and 65 deaths statewide. COVID-19 activity is currently classified as "low" nationally, but wastewater surveillance suggests viral persistence in several Montana communities.
2024-2025 Season Impact
Pertussis (Whooping Cough)
Active Circulation: Since late 2024, Montana has recorded over 140 cases across 13 jurisdictions. The outbreak is characterized by cyclical spikes, with recent alerts issued for Missoula and surrounding areas.