Molecular and Epidemiological Aspects of Dengue Virus Infection and its Vector Dynamics in Pakistan

Abstract

Dengue is the most widespread and clinically important systemic arboviral infection of humans transmitted through the Aedes mosquitoes . There are presently no particular therapeutics or licensed vaccines and considerable vector control attempts have not prevented its instant emergence and global incidence. The current global distribution of the risk of DENV infection and its public health burden are poorly recognized. However the most recent study approximated t hat 390 million of DENV infections occur annually round the globe. There are four distinctive serotypes of dengue virus, DΕNV-1, DΕNV-2, DΕNV-3 and DΕNV-4, and every single serotype is able of causing clinical disease in the form of dengue fever (DF) and severe dengue (DHF/DSS). In view of the key role dengue surveillance plays in the dissemination of the viruses, it is evident that alone passive surveillance will not reveal necessary facts required for the prediction of an outbreak in a given setting and the suggestion for an active surveillance system has been encouraged by the WHO. Virological surveillance would be directed on individuals with unspecific viral complications, such as DF, DHF or DSS and on all patients with a deadly outcome subsequent to a viral syndrome. Therefore we aims to undertake situation analysis with respect to entomological, virological, epidemiological and serological aspects of dengue/DHF in study areas for confirmation of etiology of the infection and aiming at identification of the infective virus serotype and their corresponding genotypes. A total of 914 DENV infected blood samples were collected from patients at health care centers in different geographic regions of Pakistan along with a brief questionnaire regarding the patient’s gender, residence, clinical manifestations and travel history. The Punjab showed highest prevalence 417 (58%) followed by Khyber Pakhtunkhwa and Sindh with overall 204 (29%) and 69 (10%) of the total sero- positive cases. While the number of DENV positive samples are least in Balochistan 21 (3%). The seasonal determination surveys demonstrated that the post-monsoon period was the most affected period (n = 426, 60%), followed by the monsoon period (n = 259, 36.42%) confirmed serologically positive. A clear dynamics was noted in hemoglobin, hematocrit, leucocytes and AST level. The vector density in corresponding areas clearly reflect the number of positive cases. Our study showed that all the serotype of dengue were dominant in positive samples of dengue virus infection collected during the period of Jan. 2014-Jan. 2015. Genotypes of serotype DEN-2, DEN-3 and DEN-4 were subtype cosmopolitan, Asian II and subtype III, respectively.