Table 1.

Serological Characteristics of the Study Population

		Plaque Reduction Neutralization Titers (PRNT50)					Acute Illness
Group	Subject	Den 1	Den 2	Den 3	Den 4	JE	PCR +	Viral Culture	Den IgM/IgG
Symptomatic
	105	3443	7456	1445	162	1	No	-	<1
	230	946	441	2657	210	323	No	-	<1
	247	7925	129	8232	1	17	No	-	<1
	592	1	152	1	1	1	Yes	D1	<1
	1136	745	21	176	56	1	Yes	D3	<1
	1250	>10240	471	1962	1	71	Yes	D3	<1
	1285a	1	299	150	1	1	Yes	D3	<1
	1307	211	898	3015	1	79	Yes	D3	<1
	1413	1	1	14	1	1	No	-	<1
	1484	1	377	1	1	21	Yes	D3	<1
Subclinical
	143	1081	482	979	51	1
	177	545	1030	219	1	1
	209	562	110	452	112	64
	431	130	478	71	53	1
	585	4456	715	2619	1	1
	628	2129	1	1674	1	1
	637	1107	686	2226	1	42
	963	>10240	211	465	15	1
	982	2031	1	90	1	1
	1281	636	332	2344	1	80
	1294	1	1013	1	1	1
	1327	364	435	210	1	1
	1342	879	321	630	1	1
	1374	2658	441	451	11	42
	1402	1	261	1	1	53
	1557	1036	191	4598	1	1
	1577	16	906	124	1	1

NOTE. The PRNT50 data refer to serum taken from all subjects as part of routine serologic surveillance in January 1998. The latter three columns refer to laboratory data taken at the time of acute illness. A PRNT50 value of 1 indicates an undetectable antibody response. An IgM/IgG ratio of <1.8 indicates secondary infection, while a ratio >1.8 indicates primary infection. The PCR, Viral culture, and DENV IgM data were unavailable for the subclinical group as these are routine tests during symptomatic infection.

^aHospitalized; did not meet WHO criteria for DHF.