CDC Report Finds Enhanced Tracking Uncovered 39 Group A Strep Cases Among Unhoused Missoula Residents
The CDC Morbidity and Mortality Weekly Report released findings on October 29, 2026, showing that public health officials in Montana identified 39 Group A Streptococcus (GAS) cases among 36 people experiencing homelessness in Missoula County between July 2024 and September 2025. The Montana Department of Public Health and Human Services requested assistance from the Centers for Disease Control and Prevention after routine monitoring linked initial cases to two local shelters. By reviewing facility medical records and directly collecting lab reports, officials uncovered 18 cases that standard surveillance missed. The estimated rate of GAS infection among unhoused residents was 106.1 times higher than the rate in the county general population. Of the 39 infections in people experiencing homelessness, 34 required hospitalization, and one person died from an invasive strain. The Montana Department of Public Health and Human Services has now added routine collection of housing status data to its disease investigations to detect severe infections faster.
What was announced
Between July 27, 2024, and September 20, 2025, public health agencies tracked 69 Group A Streptococcus (GAS) infections in Missoula County, Montana. A report published by the CDC Morbidity and Mortality Weekly Report details how researchers from the CDC, the Montana Department of Public Health and Human Services, and local health authorities analyzed the outbreak.
Routine public health monitoring initially tracked 20 cases tied to two Missoula homeless shelters between November 2024 and August 2025. In September 2025, state officials launched expanded surveillance efforts with CDC technical support. Staff gathered lab reports directly from healthcare facilities, examined patient history notes, and analyzed bacterial DNA samples.
This expanded review identified 39 total cases among 36 people experiencing homelessness, including three reinfections. Retrospective record reviews accounted for eight of those cases, while direct lab submissions and medical chart notes added another ten. Among unhoused patients, 34 required hospital care, 15 developed invasive disease, and one died. Wounds or skin breakdown were present in 87% of these patients at diagnosis, and 69% had a documented history of substance use. Genetic analysis of 23 bacterial samples showed six distinct M protein gene types, pointing to multiple separate chains of transmission.
What it means
Standard reporting systems often miss housing information, which hides how severe bacterial outbreaks spread within vulnerable groups. By directly reviewing shelter records and clinical documentation, state and local health teams doubled their detection rate of severe bacterial infections in unhoused residents.
Group A Streptococcus can cause skin infections as well as invasive disease, a severe condition where bacteria reach deep tissues or the bloodstream. Unhoused individuals faced an estimated infection rate of 2,285.2 per 100,000 person-years, compared to 21.5 per 100,000 among housed Missoula County residents. Because missing home addresses often hides these cases during standard hospital reporting, Montana state officials now systematically gather housing data during invasive infection investigations.
What the announcement does not tell us
The report notes several limitations. It does not state the exact overall number of unhoused residents living in Missoula County during the study window, relying instead on a 2024 local estimate of 1,484 people.
The authors explicitly mention that these figures likely underestimate true infection rates. Differences in how unhoused residents access healthcare and incomplete hospital documentation mean some cases were probably missed.
The announcement does not outline specific clinical treatment outcomes for every patient beyond hospitalization numbers. It also does not specify what thresholds Montana will use to start or stop enhanced surveillance activities during future disease outbreaks.
How this was written
This analysis was written with AI from the official announcement below, using only facts that announcement states. The quoted wording is CDC Morbidity and Mortality Weekly Report’s own. Always check the original before acting on anything here.
The Morbidity and Mortality Weekly Report (MMWR) Series is prepared by the Centers for Disease Control and Prevention (CDC).
Opens tools.cdc.gov
More from CDC Morbidity and Mortality Weekly Report
This content is for informational purposes only and is not medical advice. It is not intended to diagnose, treat, cure, or prevent any disease. Consult a healthcare professional before starting any supplement, treatment, or program: especially if you are pregnant, nursing, taking medication, or managing a health condition.