By Gabrielle Repik, Assistant Biosafety Manager
A recently published study in the Journal of Infection investigates the factors that contribute to fatalities and large outbreaks resulting from laboratory-associated incidents involving infectious pathogens. In “Determinants of fatalities and secondary transmission in laboratory pathogen incidents, 1900-2025” (PMID:42191029) , Dr. Dhawan and team analyzed 1,126 documented biosafety incidents worldwide between 1900 and 2025, including laboratory-acquired infections (LAIs), personnel exposures, accidental pathogen releases, and near-miss events. Their objective was to determine which biological, operational, personnel-related, and environmental factors are associated with two severe outcomes: death and laboratory-associated outbreaks involving five or more epidemiologically linked cases.
The researchers compiled data from multiple international sources, including PubMed, biosafety databases, and outbreak reporting systems. They examined variables such as pathogen type, pathogen risk group, laboratory facility type, biosafety level, personnel role, accident cause, transmission route, geographic region, and country income status. To identify patterns and predict outcomes, they used three analytical approaches: multivariate logistic regression (MLR), classification and regression trees (CART), and random forest (RF) machine-learning models.
Among the 1,126 incidents studied, 81 (7.2%) resulted in fatalities and 148 (13.1%) led to significant outbreaks. Fatal outcomes were strongly associated with the biological characteristics of pathogens. Prions and Risk Group 4 (RG4) pathogens, which include some of the most dangerous infectious agents, had the highest mortality risks. Certain accidental causes, particularly inadequate pathogen inactivation, wastewater or aerosol leaks, and failures in personal protective equipment (PPE) or containment measures, were also strongly linked to deaths.
Personnel roles influenced risk as well. Microbiologists, researchers, and technicians were more frequently associated with fatal outcomes, possibly because they routinely handle high concentrations of pathogens.
Outbreak risk showed a different pattern. Rather than pathogen virulence, outbreaks were more strongly influenced by operational and contextual factors. Geographic region was a major determinant, with incidents in Asia and Eurasia showing significantly higher outbreak probabilities than those in North America. Inadequate pathogen inactivation and decontamination procedures, poor waste management, wastewater, or aerosol leaks were important contributors to outbreak occurrence. Animal handling and certain laboratory procedures, such as isolation and propagation of pathogens, also increased outbreak risk. In addition, outbreak risk can further be influenced by post-exposure behavior of personnel, such as reporting practices and contact patterns.
Among the predictive models, the random forest algorithm performed best, achieving area-under-the-curve (AUC) values of 0.814 for fatality prediction and 0.799 for outbreak prediction. This model demonstrated the highest accuracy and stability across validation tests.
The study concludes that fatalities and outbreaks arise through different pathways. Mortality is primarily driven by pathogen virulence and exposure severity, while outbreaks depend more on laboratory practices, personnel behavior, institutional response, and environmental context. The authors argue that biosafety risk assessments should evaluate severity and transmission potential separately and develop targeted interventions for each. They emphasize that improving operational practices, training, containment procedures, and reporting systems is essential to reducing both deaths and laboratory-associated outbreaks.