Disease Outbreak News: Dengue – Global Situation (30 May 2024) – World

Situation at a glance

As of 30 April 2024, over 7.6 million dengue cases have been reported to WHO in 2024, including 3.4 million confirmed cases, over 16 000 severe cases, and over 3000 deaths. While a substantial increase in dengue cases has been reported globally in the last five years, this increase has been particularly pronounced in the Region of the Americas, where the number of cases has already exceeded seven million by the end of April 2024, surpassing the annual high of 4.6 million cases in 2023. Currently, 90 countries have known active dengue transmission in 2024, not all of which have been captured in formal reporting. In addition, many endemic countries do not have strong detection and reporting mechanisms, so the true burden of dengue globally is underestimated. In order to control transmission more effectively, real-time robust dengue surveillance is needed to address concerns about potential undetected cases, co-circulation and misdiagnosis as other arboviruses, and unrecorded travel movements. These factors could contribute to unrecognized disease spread and establish a potential risk for local transmission in non-endemic countries. Dengue virus is transmitted to humans through the bite of infected mosquitoes. Cases are most commonly asymptomatic or result in mild febrile illness. However, some cases will develop severe dengue, which may involve shock, severe bleeding or severe organ impairment. To strengthen global surveillance, and monitor temporal trends and disease incidence, WHO has established a global dengue surveillance system with monthly reporting across all WHO regions with a new dashboard now live (https://worldhealthorg.shinyapps.io/dengue_global/). The overall capacity for countries to respond to multiple, concurrent outbreaks continues to be strained due to the global lack of resources, including shortages of good quality dengue diagnostic kits for early disease detection, lack of trained clinical and vector control staff and community awareness. Emergency response mechanisms have been established, and WHO supports high-risk countries across affected regions. Given the current scale of the dengue outbreaks, the potential risk of further international spread and the complexity of factors impacting transmission, the overall risk at the global level is still assessed as High and thus dengue remains a global threat to public health.

Description of the situation

Global overview

Current situation

As of 30 April 2024, over 7.6 million dengue cases have been reported to WHO in 2024, including 3.4 million confirmed cases, over 16 000 severe cases, and over 3000 deaths. While a substantial increase in dengue cases has been reported globally in the last five years, this increase has been particularly pronounced in the Region of the Americas, where the number of cases has already exceeded seven million by the end of April 2024, surpassing the annual high of 4.6 million cases in 2023. Furthermore, this is three times what was reported during the same period in 2023, highlighting the acceleration of this health problem. Dengue virus is transmitted to humans through the bite of infected mosquitoes. Cases are most commonly asymptomatic or result in mild febrile illness. However, some cases will develop severe dengue, which may involve shock, severe bleeding or severe organ impairment.

The risk of dengue is similar across regions, countries, and within countries. Factors associated with an increasing risk of dengue epidemics and spread to new countries include:

• early start and longer duration of dengue transmission seasons in endemic areas;
• changing distribution and increasing abundance of the vectors (Aedes aegypti and Aedes albopictus);
• consequences of climate change and periodic weather phenomena (El Nino and La Nina events) leading to heavy precipitation, humidity, and rising temperatures favouring vector reproduction and virus transmission;
• changes in the circulating serotypes within a country affecting population immunity;
• fragile health systems amid political and financial instability in countries facing complex humanitarian crises and large-scale population movements impairing the public health response;
• movement of people who are infected and goods that could carry the mosquito vectors.

Currently, 90 countries have known active dengue transmission in 2024, not all of which have been captured in formal reporting. In addition, many endemic countries do not have strong detection and reporting mechanisms, so the true burden of dengue globally is underestimated. In order to control transmission more effectively, real-time robust dengue surveillance is needed to address concerns about potential undetected cases, co-circulation and misdiagnosis as other arboviruses, and unrecorded travel movements. These factors could contribute to unrecognized disease spread and establish a potential risk for local transmission in non-endemic countries.

To strengthen global surveillance, and monitor temporal trends and disease incidence, WHO has established a global dengue surveillance system with monthly reporting across all WHO regions, which is now available as a dashboard. This has so far captured 103 countries (Figures 1 and 2) including 28 zero reporting countries. No autochthonous or locally transmitted dengue cases have been reported in Europe so far in 2024 but these data will be added when autochthonous cases occur, which can occur when seasonal conditions permit vector activity from June to November.

Given the current scale of the dengue outbreaks, the potential risk of further international spread and the complexity of factors impacting transmission, the overall risk at the global level is still assessed as Highand thus dengue remains a global threat to public health.