Incidence of confirmed and suspected dengue cases and expansion factors.

12–9 years old in 2004–5, 2–10 in 2005–6, 2–11 in 2006–7 and 2–12 in 2007–9 (the cohort aged by one year each year).2Includes all subjects active in the cohort for at least half of the study year, whether or not an annual sample was taken at the end of the year.31–14 years old in 2004–5 and 2–14 years old for all other years.4Expansion factor = PDCS incidence of confirmed dengue/Managua NES incidence of confirmed dengue.5Includes suspected cases that met WHO criteria (see Materials and Methods); cases of undifferentiated fever, which account for 25% of laboratory-confirmed dengue cases in the PDCS, are not included in this figure.6Suspected dengue cases are defined by the NES according to WHO criteria (see Materials and Methods).7Expansion factor = PDCS incidence of suspected dengue/Managua NES incidence of suspected dengue.8Includes symptomatic cases identified only among those subjects who completed the study year and for which paired annual samples were available for determination of inapparent infection (n = 152, of 159 symptomatic dengue cases among cohort participants identified in 2004–8).