Cosmopolitan A1 lineage of dengue virus serotype 2 is circulating in Pakistan: A study from 2017 dengue viral outbreak.

Dengue viral infection has become a challenge in tropical and subtropical countries where dengue virus is endemic. Its epidemics are occurring at higher rates amid its circulation throughout the year. Since the first documented outbreak in Pakistan in 1994, this region has reported many sporadic cases and epidemics. There is availability of small scale demographic and epidemiological studies on dengue viral infection in Pakistan. The year 2017 witnessed a huge dengue outbreak in Peshawar city of Pakistan with 69 deaths and 24 807 laboratory-confirmed cases. We suspect that the circulation of a different lineage or genotype could be responsible for the enhanced number of infected patients in Pakistan's 2017 outbreak since previous studies have already described this phenomenon in other countries. For this, we collected 1447 suspected blood samples and their epidemiological data. After serotyping through polymerase chain reaction nine samples of Dengue virus2 (DENV2) were randomly selected and were subjected to Sanger's sequencing for genotyping analysis. The mean distance, genetic diversity, and phylogenetic analysis were carried out using K2 model. The phylogenetic analysis split Pakistani isolates into two lineages, the sequences from 2017 outbreak in Peshawar grouped within A1 lineage of cosmopolitan genotype (IV) of DENV2. The difference in distance, genetic diversity, and amino acids composition strongly back the results that the new lineage is circulating in the region. This is significant as Pakistan is struggling to control dengue epidemics which have caused much loss in both monetary and health sectors.