ABSTRACT
To study the genetic variability of DEN-4 Chinese isolates, and to trace the origin of DV4 Chinese isolates, we cloned and sequenced the NS2a-NS2b junction of 5 isolates and prototype DV4 (H-241). Our results show that isolates from the 1990 Guangdong epidemic, which were isolated in the early, middle, and late periods of the epidemic, share the same sequence in the NS2a-NS2b junction. The sequence similarity between isolates from the Guangdong epidemic in 1990 and DV4 H-241 is 96%; these isolates can be grouped into genotype I. The sequence similarity between the isolate from the Guangdong epidemic in 1987 and Dominica strain 814669 is 96%; this isolate can be grouped into genotype II. For the first time, our results show that there are also 2 DV4 genotypes in the Guangdong area of southern China, and these isolates perhaps were introduced from other epidemic areas outside of China.