A retrospective investigation for the seroprevalence of Chikungunya virus and its co-existence with Dengue virus in Pakistani population, 2014–2015

Dengue and Chikungunya are caused by the same vectors, Aedes aegypti and Aedes albopictus. Both mosquitoes are endemic in Pakistan, and various parts of the country experienced outbreaks of Dengue virus over the past decades. However, Chikungunya infection remained either unidentified or misdiagnosed before its outbreak in Karachi during 2018-19. This study aimed to determine the seroprevalence of Dengue virus (DENV) (a flavivirus) and Chikungunya virus (CHIKV) (an alphavirus) in suspected samples of the Pakistani population collected during 2014-2015. Immunological and molecular methods were used for the diagnosis of DENV and CHIKV. The serum samples of both healthy and febrile participants were tested for prior exposure to CHIKV and DENV using indirect IgG ELISA. The current infection of DENV was diagnosed by the presence of NS1 antigen (ELISA) and IgM (ELISA), whereas the active infection of CHIKV was identified by the presence of viral RNA (RT-PCR) and IgM. The seroprevalence of DENV and CHIKV as a single infection was 70% and 17%, respectively. However, 6% of febrile patients tested positive for both DENV and CHIKV, representing co-existence and co-infection of DENV and CHIKV during 2014-2015 in Pakistan. The presence of DENV and CHIKV co-infection evidently proved that CHIKV also caused infection during 2014-15 before its known outbreak of 2018-19. This study addressed gap analysis and highlighted the need for a comprehensive diagnostic approach and facilities in Pakistan for other arboviruses like Zika virus the virus shares the same vectors. In conclusion, developing countries like Pakistan must gain competence in response and preparedness to face future probable co-infection outbreaks of DENV, CHIKV, and other arboviruses in Pakistan. Further surveillance and epidemiological studies are required to determine the true burden of these infections and the spectrum of diseases associated with these exposures.