Table 4. Dengue virus enhancement activities in serum samples obtained from patients with secondary dengue infection and from selected non acute dengue patients.

Patienta	PatientNo.	Fold enhancementb
		DENV-1	DENV-2	DENV-3	DENV-4
Infecting serotype: DENV-1	46	0.7	0.1	0.9	5.6
	47	5.6 c	2.1	5.1	1.1
	48	4.7	2.0	5.3	4.4
	49	1.2	<0.1	1.0	2.0
	56	2.8	1.6	4.2	6.9
	57	1.2	<0.1	1.5	4.7
	58	5.3	<0.1	4.9	6.0
Infecting serotype: DENV-3	39	<0.1	2.3	1.5	6.1
	40	1.9	<0.1	1.1	4.6
	41	5.5	<0.1	5.7	6.5
	42	0.6	<0.1	1.7	1.4
	43	0.5	0.9	1.9	5.3
	44	1.5	<0.1	4.3	7.3
	45	0.7	<0.1	0.8	5.9
	52	1.5	<0.1	1.0	0.9
	53	5.2	0.2	1.4	4.7
	54	0.8	<0.1	2.0	5.0
	55	5.2	0.2	6.7	6.9
Non acute DENV d	15	1.0	4.1	4.3	5.4
	23	2.5	<0.1	1.3	4.4
	28	0.2	2.4	4.1	5.5
	30	3.2	0.1	2.5	6.1
	38	5.1	<0.1	6.3	5.6
	73	<0.1	1.5	4.3	7.3
	74	<0.1	1.2	1.1	2.5
	77	<0.1	1.9	1.3	6.7
	78	1.7	<0.1	1.3	4.7
	79	1.8	1.4	<0.1	6.6

^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.