Emergence and expansion of dengue in Paltas: possible implications of the COVID-19 pandemic and climatic variations.

Introduction: Dengue is one of the most widespread arboviruses in Latin America and is now affecting areas previously free of transmission. The COVID-19 pandemic and climatic variations appear to have affected the incidence of the disease, abundance of vectors and health programs related to dengue in some countries.

Objective: To analyze the epidemiology of dengue in Paltas, Ecuador (2016-2022), compare the periods before and during the COVID-19 pandemic, examine entomological reports and discuss the possible implications of the COVID-19 pandemic and climatic variations.

Methodology: In this observational, retrospective study, cases of dengue registered in the SIVE-Alert epidemiological surveillance system and the available larval indices were examined.

Results: No autochthonous cases were reported before 2016. Between 2016 and 2022, 182 cases without warning signs were reported, mostly in women (51.1%), people ≥ 20 years (68.7%) and people living in urban areas (78.6%). During the COVID-19 pandemic, there was a significant decline in cases in urban areas, with displacement toward rural areas (p < 0.001). A clear pattern of dengue incidence was observed throughout the year, with a predominance (84.6%) in epidemiological weeks 16-39 (April-September), which coincided with the dry season in the region. In 2016 and 2018, larval rates were high in urban areas but decreased in 2019. Postpandemic incidence rates increased in urban and rural areas, even in areas without transmission of the disease.

Conclusions: There is a clear pattern of incidence of dengue in the dry season in the region. After the 2016 outbreak, larval cases and rates decreased, suggesting the effectiveness of vector control before the COVID-19 pandemic. However, during the pandemic there was a resurgence in dengue with expansion in rural and urban areas. The increase in larval rates during the COVID-19 pandemic, even in dengue-free areas, is worrisome. A critical challenge in the control of mosquito breeding sites is climatic variations, which increase the need to reserve water for domestic use.