If during the H1N1 outbreak doctors misclassified diarrhea cases, these cases are more likely to come from those where the cause is unknown (ICD-10 code A09X) and much less so, if at all, from those where the cause is known (ICD-10 codes A00-A08) (see Appendix Table 2 in Supplementary material for details about specific ICD-10 codes).