Shifting dynamics of Dengue in Ningbo City, China: Impacts of ENSO and Interventions before, during and after the COVID-19 pandemic

Ningbo City, historically non-endemic for dengue, indigenous cases emerged between 2015 and 2020. The persistence of the El Niño phenomenon has further elevated the risk, which is compounded by the influx of visitors for the forthcoming 19th Asian Games, potentially heightening the likelihood of indigenous transmission. In response to these challenges, a series of interventions are implemented during and after the COVID-19 pandemic. We investigated the changes in dengue dynamics and variations in meteorological factors influenced by ENSO between 2017 and 2023. We observed that there is no recurrence of indigenous transmission in the post-COVID-19 pandemic period. Individuals aged 30–39 and older, as well as unemployed, retired individuals, and residents of Haishu District and Yinzhou District, exhibit a higher risk of dengue infection. A consistent decrease in onset to diagnosis interval is observed over the study period. Trends indicated an increase in Aedes mosquito density in Yinzhou, Haishu, and Fenghua districts, contrary to a significant decline in all other districts. Aedes mosquito population density is associated with temperatures, precipitation, and other meteorological factors. Despite the rising temperatures, precipitation, and population density growth, the previously escalating Aedes mosquito population density has been effectively controlled during the post-COVID-19 period. The dynamic model demonstrates that without interventions during the post-COVID-19 era, there is a risk of the resurgence of indigenous cases. Our analysis demonstrates that the reemergence of indigenous dengue cases in Ningbo City before the COVID-19 pandemic is effectively controlled through continual enhancements in preventive and control measures during and after the COVID-19 pandemic. These findings indicate that despite the rising dengue risk and the recent global surge in dengue cases, effective dengue control can be attained through the consistent adaptation and optimization of interventions.