Is dengue the only arbovirus circulating in Pakistan? Report from southern region of the country

Abstract

Background: Pakistan, has been an epicenter of Dengue (DENV) virus infection with reports of DENV epidemic outbreaks every year. Previously, it has been indicated that despite clinical features suggestive of dengue virus up to 13.49% of population tested for dengue remain negative. Since other arboviruses are not commonly tested in diagnostic labs in Pakistan, the etiology of majority of DENV negative cases remains unknown, and these patients are often said to be suffering from DENV like illness by the clinicians. Methods and materials: Patients presented with DENV and DENV like illness, were prospectively enrolled in this study after taking formal consent. Patients (n = 995) were recruited over period of April 2015 to December 2016. The diagnostic algorithm included testing for DENV infection using NS1 Pan Bio Rapid Detection kit for all recruited patients. Sample tested negative for DENV were tested for above-mentioned arboviruses using InBios ELISA kit for IgM antibodies and BioRad real time PCR. Results: Overall, 17.1% (n = 170) patients tested positive for DENV NS1. Large majority of these patients, 15% (n = 149) were residents of Karachi. Amongst the DENV negative samples, 64.7% (n = 644), 12.2% samples were positive for WNV followed by 9.9% CHIKV, 6.3% ZIKA and 4.3% JEV for IgM antibodies by ELISA. In a previous study, 105 samples that were positive for WNV IgM were evaluated for neutralizing antibodies specific for JEV and WNV by performing PRNT. Thirty-six (33.96%) exhibited greater neutralization when the minimum neutralization was set at 80%. Q-PCR positive signals were however detectable for 2.2% DENV and 3.1% CHIKV only. From demographic point of view, the age group most vulnerable was between 21 and 30 years, the IgM positivity was 24% for the overall sex distribution. Conclusion: Our results show that WNV, CHIKV, JEV and ZIKAV are actively cocirculating along with DENV in the southern region of Pakistan. The age groups between 21 and 30 years are most vulnerable, especially in the densely populated city of KHI where cleanliness and hygienic conditions are scarce. Moreover, there is a great need for the standardization of diagnostic and confirmatory assays such as PRNT for Pakistan, where WNV. JEV and other flaviviruses co-circulates with DENV.