The technical appendix discusses the methods used to estimate underreporting multipliers for both passive and outbreak surveillance data in the United States. For passive surveillance, the approach involves using simple ratio estimation to scale reported case counts to estimated numbers if they had been reported through active surveillance. The study considered 9 pathogens with available passive surveillance data from the National Notifiable Disease Surveillance System (NNDSS) and the Cholera and Other Vibrio Illness Surveillance System (COVIS). The underreporting multipliers were derived from empirical distributions of active to passive surveillance ratios, with bacterial and parasitic pathogens treated separately. For bacterial pathogens, the PERT distribution was set as low=0.9, modal=1.1, high=1.3, while for parasitic pathogens, it was low=1.0, modal=1.3, high=1.6. For outbreak surveillance, the study used 5 pathogens with only outbreak data from the Foodborne Disease Outbreak Surveillance System (FDOSS). The approach involved computing ratios of total laboratory-confirmed case counts in FoodNet active surveillance to outbreak-associated cases. The multipliers were derived from empirical distributions of active to outbreak case count ratios, with no distinction made between bacterial and parasitic pathogens due to the small sample size and lack of epidemiological or surveillance arguments for differentiation. The final PERT distribution for the multipliers was set to have a mean of 25.6, with a minimum of 5, a mode of 16, and a maximum of 237. This distribution was chosen to achieve a target mean of 25.5, considering the uncertainties in modeling the adjustment factor.The technical appendix discusses the methods used to estimate underreporting multipliers for both passive and outbreak surveillance data in the United States. For passive surveillance, the approach involves using simple ratio estimation to scale reported case counts to estimated numbers if they had been reported through active surveillance. The study considered 9 pathogens with available passive surveillance data from the National Notifiable Disease Surveillance System (NNDSS) and the Cholera and Other Vibrio Illness Surveillance System (COVIS). The underreporting multipliers were derived from empirical distributions of active to passive surveillance ratios, with bacterial and parasitic pathogens treated separately. For bacterial pathogens, the PERT distribution was set as low=0.9, modal=1.1, high=1.3, while for parasitic pathogens, it was low=1.0, modal=1.3, high=1.6. For outbreak surveillance, the study used 5 pathogens with only outbreak data from the Foodborne Disease Outbreak Surveillance System (FDOSS). The approach involved computing ratios of total laboratory-confirmed case counts in FoodNet active surveillance to outbreak-associated cases. The multipliers were derived from empirical distributions of active to outbreak case count ratios, with no distinction made between bacterial and parasitic pathogens due to the small sample size and lack of epidemiological or surveillance arguments for differentiation. The final PERT distribution for the multipliers was set to have a mean of 25.6, with a minimum of 5, a mode of 16, and a maximum of 237. This distribution was chosen to achieve a target mean of 25.5, considering the uncertainties in modeling the adjustment factor.