A new analysis of more than a century of laboratory biosafety incidents found that disease outbreaks are closely linked to operational failures, lab settings, and type of personnel involved. The findings also suggest that deaths associated with accidental lab exposures were driven largely by the virulence of the organisms involved.
For the study, published this week in the Journal of Infection, researchers led by a team at the Mahidol University in Bangkok, Thailand, analyzed 1,126 laboratory-associated incidents worldwide from 1900 to 2025. The researchers identified 148 outbreaks and 81 related fatalities.
Failure to inactivate pathogens major outbreak risk factor
Personnel type was a main factor in determining if a biosafety event turned into an outbreak. Microbiologists (odds ratio [OR], 0.1), lab techs (OR, 0.2), and veterinarians and support staff (OR, 0.3) were less likely than clinicians to be involved in incidents that triggered outbreaks.
The strongest overall predictor of outbreak risk was the cause of the incident. Causes most often associated with outbreaks included failures to fully inactivate dangerous pathogens before handling them (OR, 99.8), leaks involving wastewater or infectious aerosols (OR, 5.9), and poor decontamination or waste handling (OR, 4.4).
The researchers also found that certain lab activities carried different levels of risk. Handling animals increased the chances of an outbreak (OR, 3.8), while antibody testing and routine sample processing were linked to lower risk.
Lab type also mattered. Clinical (OR, 2.5) and academic (OR, 3.5) labs were more likely than research labs to experience outbreaks. Biosafety level (BSL) 2 and 3 facilities were protective in multivariate logistic regression analyses, but BSL was deemed of low import.
The type of pathogen had a limited influence on outbreaks. Fungal pathogens were linked to lower outbreak risk than viruses, while higher-risk pathogens showed only weak links to outbreak risk.
Inadequate inactivation raised odds of death nearly 150-fold
Fatal outcomes were strongly tied to pathogen characteristics, including risk level and type. Deaths were especially linked to work involving prions (OR, 189.9), which are infectious agents that lead to fatal neurodegenerative diseases; or RG4 pathogens (OR, 32.4) such as Ebola virus, which can cause lethal human diseases.
The biggest factor in determining whether an incident turned deadly was the type of lab accident. Compared with needlestick injuries, for example, the strongest links to fatal outcomes were failures to fully inactivate dangerous pathogens before handling them (OR, 148.2) and leaks involving wastewater or infectious aerosols (OR, 64.9). Ineffective use of personal protective equipment was also strongly linked to fatal outcomes (OR, 18.2).
The second biggest factor in predicting incident-related deaths was personnel type. Microbiologists and technicians were more often linked with fatalities than were clinicians.
Incident-specific models could improve containment
“Mortality is primarily driven by pathogen virulence, whereas outbreaks reflect operational and contextual factors,” the authors write. “Risk assessment frameworks should address severity and transmission as distinct but complementary domains.”
Risk assessment frameworks should address severity and transmission as distinct but complementary domains.
Using models that predict specific types of lab accidents could help inform biosafety programs and may improve training and containment measures, say the researchers. But, they caution, the approach should be tested in more parts of the world to ensure it works reliably in different settings.
