Short communication: Virological and B cell profiles of chikungunya and Dengue virus co-infections in Delhi during 2017-2019.

With explosive epidemics of chikungunya in India since 2004, chikungunya virus (CHIKV) now co-circulates in geographical areas where Dengue virus (DENV) is already endemic and thus provides opportunity for the same mosquito to be infected with both viruses. Although there are excellent studies that have addressed the clinical of mono and co-infection, we have little to no knowledge on the current viral sequences that pre-dominate co-infections, and the B cell response elicited. In this study, we analyzed febrile patients that were confirmed to have DENV-CHIKV co-infections and asked the following questions: 1) what is the frequency of co-infections found in a single cycle of transmission; 2) what are the viral sequences associated with them; 3) what does the antibody secreting cell / plasmablast response look like in patients that are co-infected with both viruses. We report those co-infections occur at a frequency of 6.7% in the transmission cycle, and while DENV-3 is now frequently detected, we do not see a serotype bias in the patients that are co-infected with ESCA strain of CHIKV. Moreover, the effector B cell response (plasmablasts) observed are specific to both infecting viruses indicating no overt bias. Further studies to associate whether any of these properties have a bearing on clinical disease manifestation will be both timely and important.