Characteristics of confirmed dengue cases, Cohort Study, 2004–10, and Hospital Study, 2005–2010.

1Incidence has only been calculated in the cohort study, in which between 3,497 and 3753 subjects were active in each of the six study years, corresponding to symptomatic dengue incidence of 0.48% in 2004–5, 1.82% in 2005–6, 0.37% in 2006–7, 1.82% in 2007–8, 0.59% in 2008–9 and 4.61% in 2009–10.2In the cohort study, serotype is known for 14 cases in 2004–5, 56 cases in 2005–6, 10 cases in 2006–7, 62 cases in 2007–8, 21 cases in 2008–9 and 170 cases in 2009–10. In the hospital study, serotype was identified in 46, 43, 69, 139 and 197 cases in years 2005–6 through 2009–10, respectively.3In the cohort study, immune response is indeterminate for one case in each year, 2006–7, 2007–8 and 2008–9, and in 6 cases in 2009–10. In the hospital study, immune response is known in 55, 46, 72, 147 and 203 cases in years 2005–6 through 2009–10, respectively.4In 2005–6 and 2006–7, cases requiring intensive care were not documented in the hospital study.5p-values were calculated using the Chi-square tests except for mean age and mean day of presentation, for which Mann-Whitney t-tests were applied.