Climate and dengue transmission in Grenada for the period 2010-2020: Should we be concerned?

The impacts of climate change on vector-borne and zoonotic diseases (VBZD) are well founded in some countries but remain poorly understood in Caribbean countries. VBZD impose significant burdens on individuals and healthcare systems, heightening the need for studies and response measures to address epidemics and persistent high prevalence of these diseases in any region. This study analyses the pattern of dengue case distribution in Grenada between 2010-2020 and investigates the relationship between rainfall and cases. The total number of dengue cases in the wet seasons (June to December) and dry seasons (January to May) were 1741 and 458, respectively, indicating higher prevalence of the disease in wet periods. The data also shows that rainfall was not consistently higher during the typical rainy season months. The observed patterns in 2013, 2018 and 2020 show, while these were the driest years, the number of cases were higher than in other years. Two factors may explain high number of cases in the drier years (1) frequent sporadic heavy rainfall and (2) poor water storage practices in dry season. With each 30 mm unit decrease in annual rainfall, the incidence rate ratio of dengue was reduced by a factor of .108 (89.2%). The work of the Vector Control Unit is shown to be effective in managing dengue in Grenada. The study highlights the need for year-round surveillance and interventions to control the mosquito population and dengue transmission.