We adjusted each numerator by the proportion of persons without information about their date of illness onset (i.e. epidemiologic week of illness) and, in the case of ILI case-patients, for the proportion of persons who sought care multiple times per illness event as estimated by the health utilization surveys (Appendix S1). Next, we estimated the rate of influenza A(H1N1)pdm09 -associated case-patients by dividing the sum of influenza-associated decedents, SARI-case patients, and ILI-casepatients by the age-specific census population in the sentinel sites catchment during 2009 (Appendix S1) [1] . Last, we compared the probability that decedents with a history of ILI, SARI, and ILI case-patients were more likely to be of a certain age or have a preexiting medical condition using rank-sum tests and Fisher's Exact tests.