The Return of Chikungunya in Bangladesh in 2024: Implications for Future Outbreaks.

After a major outbreak in Bangladesh in 2017, chikungunya nearly vanished from its territory until its resurgence in late 2024. However, its symptomatic overlap with dengue virus (DENV), another major arbovirus, has hindered accurate diagnosis and reporting, resulting in limited molecular diagnostic efforts for chikungunya in this region. This diagnostic evaluation study aimed to detect and characterize arboviral infections at the molecular level, focusing on the re-emergence of chikungunya and implications for future outbreaks. Febrile individuals aged 5-65 years old presenting with fever onset within 2-5 days along with other corresponding febrile symptoms were prospectively recruited from the International Centre for Diarrhoeal Disease Research, Bangladesh diagnostic facilities in Dhaka, Bangladesh. After meeting inclusion and exclusion criteria, 569 of 1,280 screened individuals were enrolled, providing informed written consent/assent. Serum samples from 474 participants underwent real-time reverse transcription-polymerase chain reaction testing, revealing 213 positive cases for at least one arbovirus. Chikungunya cases totaled 55, including seven coinfections (six with DENV and the first documented chikungunya virus-Zika virus coinfection in Bangladesh). No infections were reported from January to August, with a peak in October and November. Most chikungunya virus infections (72.7%) had moderate to high viral loads, with symptoms of joint pain, myalgia, and headaches. This resurgence of chikungunya in late 2024 highlights the potential for a major outbreak in 2025, necessitating proactive measures to mitigate public health impact and ensure a robust response to this re-emerging threat.