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Objective: To develop multiplex reverse translation-polymerase chain reaction (RT-PCR) method for detection of dengue virus type 1-4., Methods: Based on the genomes sequence analysis of dengue virus type 1-4, four-pair of primers were designed. The specificity of the primers was primarily tested by searching the GenBank DNA sequence database. The optimal reaction conditions of the multiplex RT-PCR were then established. The specificity of RT-PCR was tested using the homologous yellow fever virus and Japanese encephalitis virus. 30 serum samples of dengue virus from suspected sufferers in the prevalence of dengue virus in 2003 were detected using the methods we developed., Results: Positive segments about 295, 237, 118, 347 bp could be seen in the multiplex RT-PCR production of dengue virus type 1-4, respectively. There were no positive segments in the RT-PCR productions of Japanese encephalitis virus and yellow fever virus. 25 of the 30 serum samples showed dengue virus type 1 positive results, while the sequencing results suggesting the amplification sequence having a high homology with dengue virus type 1 strain Cambodia, GD14/97 and GD05/99 (97%, 97%, 98%, respective)., Conclusion: The method of multiplex RT-PCR we established could be used for early detection and identification of dengue virus type 1-4.

Objective: To trace the infection sources of three dengue virus type 1 isolates found in Guangdong province, namely GD05/99, GD14/97 and GD23/95., Methods: According to the genomes of dengue virus type 1 S275 strain, a pair of primers was designed for amplification of the structural protein E gene of the isolated dengue virus type 1 strains by reverse transcriptase-PCR. The amplified gene fragment was then cloned into pMD18-T vector and sequenced., Results: GD14/97 and GD05/99 shared a high nucleotide homology with Cambodia (98% and 99% respectively) and may belong to the same genotype. GD23/95 had a 95% nucleotide homology with A88, higher than that with other strains. GD23\95 and A88 may belong to another genotype., Conclusion: The dengue fever outbreak in Guangdong during 1999, 1997, and 1995 may originate from the viruses from different countries.

Objective: To identify the virus isolated from Jiangmen, Guangdong province and to discuss the possible origin., Methods: Using characteristics of indirect fluorescent antibody tests (IFA), reverse transcription-polymerase chain reaction (RT-PCR), mouse neurovirulence and cell culture to identify the isolated virus. According to the nature of dengue virus type 2 NGC strain, two pairs of primers were designed. The structural protein gene of isolated dengue virus type 2 strain was then amplified by RT-PCR, cloned into pMD18-T vector and sequenced., Results: Twenty-two of 37 serum samples showed a positive reaction to dengue antibody IgG, and 36 of 37 with IgM with the highest antibody titer 1:640. Ten samples were resulted in a cytopathy on C6/36 cells and showed a neurovirulence in suckling mice when inoculated intracerebrally. The structural gene of new isolate GD19/2001 containing 2 325 nucleotides which encoded 774 amino acids. Data on nucleotide homology were 98%, 96%, 94%, 94%, 92%, 92%, 92% and 91% compared with TSV01, GD06/93, NGC and 44, ThNH81/93, 04 and GD08/98, and S1 respectively., Conclusion: The isolated virus from Jiangmen, Guangdong province belonged to dengue virus type 2, which might come from Australia.