Bacterial Contamination of Public and Household Restrooms, and Implications for the Potential Risk of Norovirus Transmission

The transmission of infectious diseases via the use of public restrooms has been previously documented. The goal of this study was to compare bacterial contamination in public vs. household restrooms and, using quantitative microbial risk assessment (QMRA), to assess the probability of infection from fomite contact with selected high-touch sites within the restrooms. Fomite surfaces in four public and four household restrooms were sampled over a period of two months. The public restrooms were in an office building occupied by 80 individuals and were considered moderate usage. The toilet seat, toilet flush handle, countertops, and floor were sampled for heterotrophic, coliform, and Escherichia coli bacteria. The highest numbers of heterotrophic bacteria and coliforms were detected on the countertops, followed by the floor. The greatest numbers of E. coli were recovered from the countertops in the household restroom, but the greatest numbers in the public restroom were recovered from the toilet flush handle. Numbers of heterotrophic bacteria and coliforms were 10 to 100 times greater in household restrooms than in public restrooms. The QMRA suggested that the greatest risk of acquiring a norovirus infection involved the touching of the countertops in household restrooms and the toilet flush handles in public restrooms.