Due to the COVID-19 pandemic and a lower reporting rate, there was a slight decline in dengue cases between 2020 and 2022. However, in 2023, there was a global upsurge in dengue cases, which was characterized by a significant increase in the number, scale, and simultaneous occurrence of multiple outbreaks that spread into previously unaffected regions.
Dengue transmission is cyclical, with significant outbreaks predicted every three to four years. We found low transmission in certain areas and moderate transmission in others during the COVID-19 pandemic, which resulted in a build-up of individuals lacking immunity to specific dengue virus serotypes. The available information on the dengue serotypes in circulation is, however, scarce.
Around 80 countries and territories, as well as five WHO regions-Africa, the Americas, South-East Asia, the Western Pacific, and the Eastern Mediterranean-have reported close to a historic high of over five million cases and more than 5000 dengue-related deaths since the beginning of 2023 due to ongoing transmission combined with an unexpected spike in cases (Figure 1). 4.1 million cases, or about 80% of all cases, have been documented in the Americas region. In the Americas, dengue is the most common arbovirus and is responsible for the greatest number of instances of arboviral disease. Epidemics of dengue typically occur every three to five years.
There is a growing likelihood that the dengue epidemic will spread due to a number of factors, such as shifting vector distribution (mostly Aedes aegypti and Aedes albopictus), particularly in countries where dengue has not yet spread; El Nino effects in 2023; climate change resulting in higher temperatures, higher rainfall, and increased humidity; brittle health systems during the COVID-19 pandemic; political and financial instability in nations dealing with complex humanitarian crises; and increased population movements. These elements also raise concerns about how the disease is being handled and the possibility of it spreading to other nations. A higher number of severe dengue cases may have resulted from inadequate monitoring systems in many of the afflicted nations, which also may have caused delayed reporting and response as well as missed symptom recognition.
