Dengue Haemorrhagic Fever in Thailand, 1998-2003: Primary or Secondary Infection

The pathogenesis of dengue haemorrhagic fever (DHF) is looked for in the serological records of DHF patients (mainly children between the ages of one month and 16 years) at Siriraj Hospital in Thailand over a six-year period beginning 1998 (covering two three-year cycles). Based on the primary and secondary infections by both the haemagglutination-inhibition assay (HI) test and the IgM capture enzyme-linked immunosorbent assay (ELISA) test, it was found that in 1998, 14 of the cases for which paired sera specimens were tested using both HI and ELISA (or 9.6% of 146 cases) had resulted from primary infections. In 1999, 2000, 2001, 2002 and the first half of 2003, three out of 57 cases (5.3%); six out of 48 cases (12.5%); 85 out of 293 cases (29%); 23 out of 90 cases (25.6%) and 16 out of 56 cases (28.6%), respectively, resulted from primary infections. The percentages of primary infections during the last three years are well above 14.0% reported for cases occurring in Bangkok between 1988 and 2003.