Concurrent transmission of Zika virus during the 2023 dengue outbreak in Dhaka, Bangladesh

Background During the 2023-dengue outbreak in Bangladesh, a diagnostic evaluation study was conducted to investigate concurrent Zika virus (ZIKV) and dengue virus (DENV) transmission in Dhaka in 2023. Aims The study explored to simultaneously detect the presence of ZIKV, DENV, and/or CHIKV while considering relevant clinical and epidemiological risk factors, using a real-time multiplex RT-PCR system. Following this, it was planned to sequence the selected samples to identify genetic variations of the ZIKV infections within the population. Methods This study was designed as a diagnostic evaluation, where participants meeting the inclusion criteria were prospectively recruited with written informed consent. A total of 399 febrile individuals were screened, with 185 meeting the inclusion criteria of having a fever onset within 2–5 days, along with one of the following clinical features, e.g. headache, myalgia, arthralgia or bone pain, rash, nausea, vomiting, or diarrhea and 152 undergoing real-time RT-PCR testing. Results Five ZIKV-positive cases were identified, including one DENV-ZIKV co-infection. Phylogenetic analysis revealed the ZIKV strains were part of the Asian lineage, closely related to Cambodian and Chinese strains from 2019. All ZIKV-positive cases were male, residing within a one-kilometer radius, with no prior travel history, suggesting community-level transmission. Conclusion This study marks the first identification of ZIKV in Dhaka city and the first report of ZIKV-DENV co-infection in Bangladesh that highlights the diagnostic challenges posed by the symptomatic similarities between ZIKV and other arboviruses and underscores the need for enhanced surveillance and public health interventions to mitigate the spread and impact of ZIKV in dengue-endemic regions.