|

Was Group A Strep Incidence 106 Times Higher? Limits of the Missoula Report

ByLife Choice Note

Short answer: A CDC report published on October 29, 2026, estimated that the incidence of group A Streptococcus (GAS) infection among people experiencing homelessness in Missoula County, Montana, was 106.1 times the rate in the county’s general population. This was a local surveillance finding based on 39 infections among 36 people from July 27, 2024, through September 20, 2025. It does not mean every unhoused person has exactly 106 times an individual’s risk, and it does not establish a new outbreak in the general population or outside Missoula.

  • Publication date: October 29, 2026
  • Place and period: Missoula County, Montana, United States; July 27, 2024–September 20, 2025
  • Population: Invasive, severe noninvasive and nonsevere noninvasive GAS cases, with emphasis on people with confirmed or probable homelessness
  • Evidence type: Enhanced public-health surveillance by CDC and Montana and Missoula health authorities—not a clinical trial

Where did the 106.1 figure come from?

Investigators identified 69 GAS infections. Thirty-nine cases (57%), including three reinfections, occurred among 36 people with confirmed or probable homelessness. The estimated incidence in that group was 2,285.2 cases per 100,000 person-years, compared with 21.5 per 100,000 person-years in the Missoula County general population. The resulting incidence-rate ratio was 106.1, with a wide 95% confidence interval of 65.9 to 170.7.

This is a comparison of detected cases standardized for population size and observation time. It is not a precise probability for any one person, and it is not a national U.S. or South Korean rate. Estimating the number of people experiencing homelessness is difficult because the population changes over time, and differences in health-care access and case finding add uncertainty.

What did enhanced surveillance find that routine systems missed?

Routine surveillance detected 20 invasive and noninvasive infections epidemiologically linked to two Missoula homeless shelters between November 2024 and August 2025. In September 2025, investigators expanded surveillance by obtaining laboratory reports and medical records directly from local facilities, systematically reviewing housing information, sequencing available bacterial isolates, and extending the surveillance period backward to July 2024.

Of the 39 infections among people experiencing homelessness, 18 (46%) were found through those enhanced methods or the longer look-back period. Eight were found by extending the period, while 10 were identified through direct laboratory data or housing information in medical records. The operational lesson is that cases in a high-risk population can remain hidden when housing status is not consistently captured.

How severe were the infections?

Thirty-four of the 39 cases (87%) among people experiencing homelessness required hospitalization. Fifteen (38%) were invasive infections—defined by bacteria in a normally sterile site or by streptococcal toxic shock syndrome or necrotizing soft-tissue infection—and one invasive case resulted in death. All three people with reinfections had invasive disease during both their first and recurrent episodes.

CDC lists wounds or skin disease, diabetes, immunocompromising conditions, older age, injection-drug use and experiencing homelessness among factors linked to serious GAS infection. Skin breakdown from injuries, burns, pressure ulcers or environmental exposure and delayed access to care may contribute. This report, however, cannot isolate the causal effect of each factor.

What does this mean outside Missoula?

The report did not measure GAS incidence in South Korea or other U.S. counties, and it is not evidence of a new general-population epidemic. Its transferable public-health message is narrower: surveillance systems may need reliable housing information, links between shelters and health facilities, accessible wound care and faster routes to evaluation for populations facing barriers to care.

GAS can cause illnesses ranging from strep throat and skin infection to sepsis, necrotizing fasciitis and streptococcal toxic shock syndrome. Rapidly spreading pain, swelling or redness, high fever, confusion or breathing difficulty warrants urgent medical assessment regardless of housing status. This article cannot diagnose an infection or direct antibiotic use.

Important limitations

  • This was a small local surveillance report: 39 infections among 36 people in one county.
  • The population denominator for people experiencing homelessness is dynamic and difficult to enumerate, making incidence estimates uncertain.
  • Infections may have been missed among people who could not access care or were not tested, potentially underestimating the burden.
  • More intensive case finding in one group than another can affect the size of the comparison.
  • Observational surveillance cannot prove that homelessness itself caused infection or establish the effect of a specific prevention program.

Primary sources

By: Life Choice Note — an independent personal health-information explainer based on official and primary sources.
Reviewed: October 30, 2026
Note: This article provides general information and does not diagnose infection or direct antibiotic choice. Discuss individual symptoms and risks with a qualified clinician.

Related guides