Dengue Virus Serotype 2 (DEN-2): the Causative Agent of 2011-Dengue Epidemic in Pakistan

Introduction: Dengue virus (DENV) is an arthropod-borne virus that belonged to the Flaviviridae viral family. Four known serotypes DEN-1 through DEN-4 do exist and circulate in diverse geographical regions of the world causing epidemics. The management of dengue patients, and especially dengue hemorrhagic fever (DHF)/Dengue shock syndrome (DSS) cases, has been a challenge in Pakistan now days. Method: We have carried out a comprehensive study of the current outbreaks of dengue virus infection on molecular level with the aim to find out the common serotype/s of DENV responsible for this outbreak using PCR, real-time PCR and nucleotide sequencing targeting the C-prM gene junction. For this purpose total 1129 serum samples received between from start of August till end of November 2011 from all the major hospitals of Lahore, Punjab at Division of Molecular Virology, National Centre of Excellence in Molecular Biology (CEMB) University of the Punjab Lahore were utilized for the DENV diagnosis and serotypes/genotypes analysis. Results: Male female ratio of the suspected dengue patients was 2.4:1. Their mean age were 31.14 + 16.03 (SD) years ranging from 9 months to 90 years. Out of these 1129 serum samples, total 930 (82.37%) were found infected with DENV. Out of the 930 DENV RNA positive samples, 893 (96.02%) had DEN-2 and 37 (3.97%) sample had concurrent infection with serotypes 2 and 3. Conclusion: Based on the results of this study we conclude that DEN-2 is the responsible genotype for the current dengue epidemic that started from the beginning of year 2011 and is continuing till now. The additional serotype detected in the current study was serotype 3 that remained in very low frequency in Pakistan for last several decades.