During the EPI-WIN Webinar: Managing Dengue: a rapidly expanding epidemic, held in August, experts from around the world highlighted that about half of the world’s population is now at risk of dengue, with an estimated 100–400 million infections occurring each year.
“Incidence has increased by almost eight-fold since 2000,” said Dr Raman Velayudhan, Unit Head for Veterinary Public Health, Vector Control and Environment and Neglected Tropical Diseases at the World Health Organization (WHO) at the opening of the webinar. Before 1970, the mosquito-vector of the disease was present in only half a dozen countries, he added, but it is now found in over 130 countries.
Situation in the Americas
In the Americas, dengue is transmitted primarily by the Aedes aegypti mosquito and the disease is endemic to many countries. Outbreaks tend to be cyclical every 3 to 5 years, following seasonal patterns corresponding to the warm, rainy months, when mosquitos breed.
In 2023, however, the Americas have seen a sharp increase in dengue cases. Over 3 million new infections have been recorded so far, surpassing figures for 2019 – the year with the highest recorded incidence of the disease in the region, with 3.1 million cases, including 28,203 severe cases and 1,823 deaths.
Most cases – over 2.6 million – are registered in the southern cone, with Brazil accounting for 80%. But unusually high transmission has also been seen in other areas of the continent, including the Andean region, with over 400,000 cases and a higher case fatality rate.
In March and June of this year, the Pan American Health Organization (PAHO) issued recommendations to help countries tackle the increase.
“Urbanization and climate change have had a huge impact in spreading dengue,” Velayudhan said during the webinar. The movement and agglomeration of people in urban areas have helped to spread the vector, he added, but COVID-19 disruptions have also impacted mosquito control measures and the reporting of cases.
“Post-COVID, we need to realign programs to be more integrated and ensure health systems can manage,” Velayudhan said. “We should implement the lessons learned from the pandemic, such as in diagnosis and use of PCR tests, enhanced surveillance, good communication and community involvement.”
Community engagement for effective vector control
There is no specific treatment for dengue, and prevention depends on the control of the vector. Measures to curb mosquitoes include the use of chemicals, such as insecticides and repellents, and mechanical methods to remove breeding sites or provide a barrier, such as treated nets, window screens and protective clothing.
Programs that use a combination of these methods can be effective, but engaging communities to apply them is critical for their success, especially to remove or clean potential breeding habitats. Old, disused tires, for example, offer shade and a preferred dark space for aedes mosquitos to lay their eggs, which can resist drought and develop only once they meet water many months later.
Dengue is a viral infection that spreads from mosquitoes to people. While most infections are asymptomatic or produce mild illness, the disease can occasionally become severe and even cause death. Symptoms range from mild to debilitating high fever, with severe headache, pain behind the eyes, muscle and joint pain, and a rash. The illness can evolve into severe dengue, characterized by shock, respiratory distress, bleeding, and possible organ impairment.
Source: PAHO