Sequence analyses of NS3 genes of recent Pakistan and Singapore strains of dengue virus types 1 and 2

Comprising four serotypes belonging to the flavivirus family, the Aedes mosquito-borne dengue viruses cause dengue fever and related diseases which pose considerable public health problems in many tropical and subtropical countries. We documented the first serologically and virologically confirmed epidemic of dengue haemorrhagic fever in Karachi, Pakistan in 1994. In recent years, Singapore has continued to experience a significant incidence of dengue fever, i.e. 1,239 cases in 1994 with a median age of 28 years, and 2,008 cases in 1995, with dengue-1 virus being the predominant type. We report here the comparative analysis of non-structural-3 (NS3) gene sequences of three dengue-1 and two dengue-2 virus isolates from the recent Pakistan and Singapore outbreaks.