Real-time PCR for detecting circulating dengue virus in the Guangdong Province of China in 2006

This study developed four serotype-specific real-time PCR assays for detecting dengue virus (DENV) serotypes 1-4 based on computational analysis of conserved sequences. The researchers tested 64 serum samples from Guangdong Province, China collected during a 2006 dengue fever epidemic. Results showed 71% positive detection rate for DEN-1, with perfect agreement between real-time PCR results, serological tests, and sequence analysis. The assays demonstrated high sensitivity and specificity without cross-reactivity between serotypes. Critically, real-time PCR proved significantly more sensitive than serological methods in early infection (days 1-3), detecting virus in 86% of samples versus only 18% for IgM antibodies. This early detection capability has important implications for patient management and epidemic control, as rapid serotype identification is essential for determining disease severity risk, particularly for secondary infections that can lead to dengue hemorrhagic fever. The assays also enabled quantification of viral loads, which decreased over time from a median of 8.29×10⁵ copies/ml in days 1-3 to 96×10² copies/ml by day 6.

Key findings

• Four real-time PCR assays for DENV serotypes 1-4 achieved high sensitivity and specificity with no cross-reactivity, detecting 40-4×10⁷ RNA copies per reaction across different serotypes.
• Real-time PCR detected DEN-1 virus in 86% of samples within 3 days of symptom onset compared to only 18% detection by IgM serology, demonstrating superior early diagnostic capability.
• Analysis of 64 clinical samples from the 2006 Guangdong epidemic confirmed DEN-1 as the causative serotype through agreement between PCR results, serology, and sequencing.
• Viral loads decreased significantly over time, from median 8.29×10⁵ copies/ml in days 1-3 to 96×10² copies/ml by day 6 post-symptom onset.
• The closed-system real-time PCR protocol reduced contamination risk compared to conventional nested RT-PCR and provided rapid standardizable results suitable for clinical laboratories.