Dengue: A re-emerging infectious disease. Lessons from Nepal

• Dengue transmission has expanded geographically in Nepal over two decades. • Multiple dengue serotypes now circulate, increasing severe disease risk. • Surveillance gaps and underreporting hinder early outbreak detection. • Climate change and urbanization are key drivers of dengue spread. • Urgent need for integrated vector control and strengthened public health. Dengue is a rapidly re-emerging arboviral disease in Nepal and has become a major public health concern over the past two decades. Since its first documented outbreak in 2004, dengue transmission has expanded geographically and intensified in frequency and magnitude, culminating in unprecedented nationwide epidemics in 2019, 2022, and 2023. This narrative review summarizes the historical emergence, epidemiology, temporal trends, and key drivers of dengue outbreaks in Nepal, with particular emphasis on climate change, unplanned urbanization, socioeconomic vulnerabilities, vector expansion, cross-border population mobility, and gaps in surveillance and preparedness. Available evidence indicates that dengue is no longer confined to the lowland Terai region; sustained transmission now occurs in mid-hill and high-altitude areas, including the Kathmandu Valley. The increasing circulation of multiple dengue virus serotypes further raises the risk of severe disease through secondary infections. Despite the existence of national guidelines and vector control initiatives, delayed outbreak detection, underreporting, and fragmented surveillance systems continue to undermine effective response. This review highlights critical weaknesses in dengue surveillance, prevention, and control strategies in Nepal. It underscores the urgent need to strengthen early warning systems, integrated vector management, community engagement, and climate-adaptive public health policies. Addressing these challenges is essential to mitigate future dengue epidemics and reduce their health and socioeconomic impacts in Nepal.