Expansion factors for hospitalized (EFH), ambulatory (EFA) and total (EFT) dengue episodes, and average annual reported and estimated dengue episodes (2001–2010).

EFs for the lower panel -based on extrapolations from neighboring countries - were estimated under the following assumptions: (i) EFH was constant and equal to the average EFH of countries in the region for which we had empirical evidence (EFH = 2.5); (ii) to estimate EFA for Bhutan, Laos, and Philippines, we also assumed that the OP∶IP episodes ratio was, on average, constant for these countries and equal to the weighted average from all empirical studies in the region (OP∶IP = 4.4).n.r. denotes not reported; SEA denotes Southeast Asia.aThe 95% certainty level reported in parentheses was estimated by a probabilistic sensitivity analysis simultaneously varying key parameters in 20,000 Monte Carlo simulations (see Table 5 to see specific parameters and distributions used for each factor in the sensitivity analysis).bWe obtained an empirical estimate for EFH of 3.4 in Singapore; however, given legal requirements and incentives for reporting, we think that this estimate may be too high. The main reason for underreporting of dengue in hospitals seems to be under diagnosis, as patients with undifferentiated fever are not routinely tested, or are tested with serological that may not pick up dengue. An additional factor behind underreporting may be underreporting in the private sector [67], which accounted for about 23 of hospitalizations in Singapore (2009–2011; Ministry of Health Singapore). To be conservative, we used the average for countries with empirical studies (2.5), and used 3.4 as the upper bound in the sensitivity analysis, as shown in Table 5.