Primary and probable secondary dengue virus (DV) infection rates in relation to age among DV IgM-positive patients residing in the United States mainland versus the Caribbean islands.

Dengue virus (DV) primary infection and probable secondary infection rates in relation to patient age (years) were determined for DV IgM-positive U.S. mainland residents (presumed travelers to areas of DV endemicity) and Caribbean island (area of DV endemicity) residents by evaluating IgG status and IgG avidity. Regardless of place of residence, most patients ≤20 years old exhibited primary infection and most patients >60 years old exhibited probable secondary infection. Among patients 21 to 60 years old, the primary infection rate was markedly higher in U.S. residents.