Dengue virus enhancement activities in serum samples obtained from patients with secondary dengue infection and from selected non acute dengue patients.

aInfecting serotype indicates the DENV serotype detected in the serum sample as determined by RT-PCR.bFold enhancement values are enhancement ratio calculated by the fornula: mean plaque count at 1∶10 serum dilution/plaque count without addition of serum using FcγR-expressing BHK cell lines.cUnderline indicates positive infection-enhancing activity. Positive infection-enhancing activity is defined as fold-enhancement value greater than cut-off value plus 2 times SD in the mean plaque count in the presence of human serum samples as compared to the cut-off value. Cut-off value was determined in the absence of serum.dSerum samples obtained from selected non acute dengue patients.