Quantitative microbial risk assessment of human norovirus infection in environmental service workers due to healthcare-associated fomites.

Structured Summary Background Healthcare associated norovirus outbreaks place a large burden on healthcare staff. Environmental service workers (ESWs), however, remain understudied despite high contact with potentially contaminated surfaces. Understanding the magnitude of norovirus risks in healthcare ESWs can protect workers and improve infection control. Aim We simulated norovirus infection risk for unprotected ESWs after a single fomite contact, assuming no disinfection or protective equipment, in norovirus positive patient rooms. We also simulated the risk of secondary surface transmission from norovirus-exposed ESWs. Methods A quantitative microbial risk assessment employing 2D Monte Carlo with parameters extracted from literature was used to estimate norovirus infection from multiple fomite contact scenarios that were defined by: norovirus source (patient vomit/ diarrhoea), location (bathroom/ patient room), and target outcome (ESW/ secondary illness). Findings Unprotected ESWs have a maximum estimated norovirus infection risk of 33% (1:3) for a single fomite contact in a room where a norovirus positive patient had a diarrhoea event. Patient vomit events lead to fomite contact risk estimates four orders of magnitude lower than those for diarrhoea events. Estimated risk of secondary illness from touching a common surface was as high as 25% (1:4) after single fomite exposure following a diarrhoea event. Conclusions A single fomite contact may lead to sizable norovirus infection risk in ESWs if personal protective equipment and disinfection are not used appropriately. ESWs can also transfer virus to secondary surfaces, initiating further infections. Interventions are needed to reduce fomite transfer of norovirus and protect patients and staff from nosocomial infections.