Early Clinical Features of Pediatric Dengue www.plosntds.org cases were defined as primary DENV infections if acute-phase antibody titer, as measured by Inhibition ELISA, was ,1:10 or if convalescent phase antibody titer was ,1:2560, and as secondary infections if the acute titer was $1:10 or convalescent titer was $1:2560 [22] [23] [24] [25] .