The early identification of dengue cases and particularly those at risk for severe dengue is critical for preventing severe illness and death. We found that 25% of laboratory-confirmed dengue cases did not meet the WHO case definition, suggesting that the WHO criteria are not sufficient to identify dengue at younger ages. Younger children may experience different signs and symptoms from adults or may be unable to communicate their symptoms to their parents, health care providers, or both. Previous studies demonstrated that children may experience significantly more cough, vomiting, abdominal pain, rash, epistaxis, oliguria, thrombocytopenia, hepatomegaly, and shock compared to adults, although the direction of these differences was not consistent across studies [13, 15, [29] [30] [31] [32] [33] [34] . A recent study of dengue in adults showed significant differences in clinical features and outcomes across ten-year age groups, indicating that signs and symptoms associated with DENV infection may continue to evolve past childhood [12] . If these differences are confirmed, the WHO case Table 3 . Signs and symptoms associated with testing DENV-positive among patients using generalized estimating equation models. Days Generalized estimating equation models assume an exchangeable correlation structure with robust standard errors. DENV, dengue virus; OR, odds ratio; CI, confidence interval; aOR, adjusted odds ratio. definition may need to be adjusted to be age-specific to function effectively for younger children and older age groups. Retro-orbital pain and low platelets were among the clinical features independently associated with DENV infection in this study. These results are supported by a study of dengue patients in Puerto Rico in which data were recorded at the time of initial consult rather than at hospitalization [15] , and by a study of Thai children [11] . Moreover, our results showing increased frequency of abdominal pain in patients beginning at day 3 of illness are consistent with a prospective study of adults admitted to an emergency department in Martinique [35] . A positive tourniquet test using cut-offs of $10 and $20 petechiae/in 2 was also independently associated with DENV infection. Both cut-offs were used because studies have indicated that a cut-off of $10 may improve discrimination of DENV infection [20, 36] ; however, the 1997 WHO classification scheme specified a cut-off of $20 [26] . Our results support using a cut-off of $10 petechiae/in 2 , and this cut-off has been specified in the 2011 WHO clinical guidelines [37] .