A composite measure evaluation of Mpox disease investigation services in Santa Clara County found that each investigation led to 1.90 outcomes achieved, with an overall composite score of 0.53, demonstrating that disease investigation services produced multiple public health outcomes simultaneously.
Key Findings
Results
The overall composite score of disease investigation services was 0.53, meaning each investigation led to 1.90 outcomes achieved across five measured outcome categories.
Five outcomes were measured: treatment completion, monitoring completion, partial vaccine dose completion, full vaccination series completion, and STI and HIV testing
Investigations were completed between June and December 2022 during the Mpox outbreak in Santa Clara County, California
The composite measure was designed to calculate the number of investigations needed to achieve each outcome
The County of Santa Clara Public Health Department activated emergency response operations including designated disease investigation (DI) services
Results
Among cases eligible for treatment, 2.16 investigations were needed to yield one treatment completion.
This metric applied specifically to cases eligible for treatment, not all cases
Treatment completion was one of five outcomes tracked in the composite measure
The number of investigations needed per outcome served as the basis for the composite scoring method
Results
Monitoring completion was the most efficiently achieved outcome, requiring only 1.19 case and contact investigations per completion.
Monitoring completion applied to both case and contact investigations
A ratio of 1.19 investigations per monitoring completion was the lowest ratio among all five outcomes measured
This suggests monitoring completion was more readily achieved relative to other outcomes per investigation conducted
Results
Partial vaccine dose completion required 2.21 contact investigations per completion, while full vaccination series completion required 3.53 contact investigations per completion.
Both vaccine-related outcomes applied specifically to contact investigations, not case investigations
Full vaccination series completion (3.53 investigations needed) was the least efficiently achieved outcome among all five measured
The difference between partial (2.21) and full (3.53) vaccination series completion reflects the added difficulty of achieving complete vaccine series in contacts
Results
STI or HIV testing required 2.25 case and contact investigations per one test completed.
STI and HIV testing was measured as a combined outcome
This outcome applied to both case and contact investigations
The ratio of 2.25 investigations per STI or HIV test placed this outcome in the mid-range of efficiency compared to other outcomes
Conclusions
The authors argue that a composite measure approach to evaluating disease investigation services can illuminate multiple simultaneous intervention impacts that single-outcome evaluations would miss.
The study noted there is 'limited research that evaluates the impact of disease investigation (DI) services'
The composite scoring method was developed to capture the range of outcomes achieved rather than a single metric
The authors conclude that 'recognizing the multiple steps involved in DI can inform holistic evaluations that illuminate intervention impact'
The evaluation framework was applied to a real-world public health emergency response context
What This Means
This research suggests that when public health departments investigate infectious disease outbreaks, their work produces multiple benefits at once — not just one outcome per case investigated. During the 2022 Mpox outbreak in Santa Clara County, California, health investigators worked with both confirmed cases and their contacts to encourage treatment, monitoring, vaccination, and HIV/STI testing. The researchers developed a scoring system to track how many investigations were needed to produce each type of positive result, finding that on average each investigation led to nearly two outcomes.
The study found that some outcomes were easier to achieve than others. Monitoring completion was the most efficient outcome, requiring just over one investigation per completion, while getting contacts to complete a full vaccination series was the hardest, requiring more than three and a half investigations per completion. STI and HIV testing and treatment completion fell in between, each requiring roughly two investigations per outcome achieved.
This research matters because it offers a new way for public health agencies to measure whether their disease investigation work is actually making a difference. Rather than counting only one metric — like how many cases were contacted — this approach captures the full range of benefits produced by investigation services. This could help health departments better understand and communicate the value of their outbreak response efforts, and potentially improve how they allocate resources during future disease outbreaks.
Agroia H, Mousli L, Nangia D. (2025). A holistic evaluation of sexual health disease investigation: case study of the 2022 Mpox outbreak in Santa Clara County, California.. Sexual health. https://doi.org/10.1071/SH24197