One of the unsatisfying things about these types of case investigations is when it comes to hypothesising non - person-to-person transmission—so transmission in an indirect route through the environment or through fomites—we don't find a smoking gun. I've been on many investigations of infection prevention and control in my previous job, and one of the things that a sensible infection prevention and control report will often do is list these hypotheses in a structured way and then identify ways in which the most plausible of them can be prevented in the future. Unfortunately, the problem in finding proof of transmission through these non-conventional or atypical means is also present in the scientific literature.