Co-circulation of dengue virus multiple serotypes during the 2022 outbreak in Madhesh Province, Nepal

Dengue virus (DENV) poses a significant public health threat in Nepal, with major outbreaks increasingly reported across the country’s southern plains. This study aimed to identify the circulating DENV serotypes during the 2022 dengue outbreak in Madhesh Province, Nepal. Out of the 588 non-duplicate serum samples, 17.86% exhibited probable acute-phase dengue infection profiles, while 5.95% revealed recent or late-stage DENV infection profiles. Similarly, 0.85% showed resolved DENV infection profiles, while 75.34% showed negative results for DENV infection. Among the 85 serologically positive dengue samples analysed for serotyping, DENV serotypes were detected and identified in 81.2% ( n = 69) samples. Dengue virus serotyping revealed the co-circulation of three DENV serotypes ( DENV-1, DENV-2, and DENV-3) in Madhesh Province, Nepal during the 2022 outbreak. DENV-1 was the predominant circulating serotype, accounting for 55.1% of the typed samples, followed by DENV-3 and DENV-2 as single-serotype infections. Furthermore, concurrent infection with DENV-1 and DENV-2 was detected in 13% of the typed samples. Concurrent DENV-1/DENV-2 infection was identified for the first time in Madhesh Province, with DENV-1 predominating among the multiple circulating serotypes.