Except that the authorities didn't investigate more than asking the guy, this makes sense to me. If there were in fact dozens of cases arising from a single person visiting a pizza shop once, that would imply the existence of the most infectious virus known to modern humans, and (like how China could have if the CCP didn't thoroughly persecute both whistleblowers and small time administrators that raise problems for help) they might have a fleeting chance to crush it before it spreads worldwide.