Virological Study on Dengue Epidemic in Vientiane Municipality, Lao PDR, 1994.

In May 1994, an epidemic of dengue fever (DF) / dengue hemorrhagic fever (DHF) was reported in Ban Horn commune in Vientiane municipality. This was after a six-year period of non-epidemic DF/ DHF in the municipality. In early June, we collected 81 serum specimens from children with fever of unknown origin (FUO) in the commune. Of 81 specimens, 48 were taken from children within 5 days after the onset of FUO and subjected to dengue (DEN) virus isolation. Four strains of DEN-1 and 12 strains of DEN-2 viruses were isolated from 15 serum specimens (31.3%). A case of dual infection with DEN-1 and DEN-2 viruses was detected by enzyme antibody method using type-specific monoclonal antibodies and reverse transcription polymerase chain reaction (RT-PCR). The percentage incidences of the positive virus isolation from the serum specimens taken on the second and the third day of fever were 41.8% and 21.1%, respectively, and no virus was isolated from the specimens other than those from these two days. All the specimens were examined by the IgM-capture ELISA. Thirty-two specimens (39.5%) were positive for DEN IgM antibody.