Because incubation periods are biologically spread over a range of days, it is possible that some cases were misclassified because we chose the incubation period limits to optimize the TRC. Cases with onset date after return might have actually been infected in Canada but classified as TRC because the delay between return and onset was below the maximal incubation period. Such cases should be very few as most TRC with onset after return became ill immediately after return (Figure 2). Misclassification was also possible for cases that were sick soon after departure. As a consequence, the proportion

of TRC among all cases might be overestimated to an unknown but presumably limited extent. Instead of relying on reported cases, the actual burden of enteric diseases should be quantified by the actual number of Volasertib in vivo cases because of the common under reporting rates of such diseases.5,33 This rate depends on the disease and it was estimated that in Canada 10 to 50 actual cases of salmonellosis, campylobacteriosis, CX-5461 and VTEC occurred when only one was actually reported.33–35 Whether the underreporting rate

is similar for TRC and other DC is a key to estimating the actual burden from the current findings. A lower actual/reported case ratios for TRC is arguable. Several studies show that cases of diarrhea with travel history (in particular to developing countries) or with severe symptoms, in particular diarrhea for 3 days or more, bloody diarrhea and fever, are more likely to present to a physician and that the physician is more likely to recommend stool to be tested.36–38 However, a medroxyprogesterone population health survey in Wales showed that cases of foodborne gastrointestinal illness acquired domestically were more likely to consult a physician compared to cases acquired abroad.9 With regard to illness severity, the findings showed that TRC were not different from DC thus not supporting differential actual/reported case ratios on the disease severity

basis. In the absence of evidence, one may consider similar or very closed underreporting ratios for both TRC and DC for the moment. From a human illness attribution perspective, traveling outside Canada is an important source for diseases caused by enteropathogens, and consequently represents a significant fraction of the burden associated with these diseases on the medical system and overall on society. Travel, as a source for human illness attribution, has been recently estimated in the Netherlands via a structured expert elicitation.7 The experts were asked to provide their minimum and maximum estimates for the attribution of 16 enteric diseases to five major transmission pathways, one being travel abroad.