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PRESS BRIEFING BY THE UNITED NATIONS INFORMATION SERVICE

22 December 2023

Global Dengue Situation

Dr. Diana Rojas Alvarez, Team Lead on Arboviruses, Epidemic and Pandemic Preparedness and Prevention Department, World Health Organization (WHO) Emergencies Programme, said dengue was the most common viral infection transmitted to humans through the bite of infected mosquitoes and was mostly found in urban areas within tropical and sub-tropical climates worldwide. However, because infected mosquitos could thrive in more countries because of increasing temperatures due to climate change, many more countries had been reporting cases this year.

About four billion people were at risk of becoming infected with the dengue virus. Most people who contracted dengue did not have symptoms. But for those who did, the most common symptoms were high fever, headache, body aches, nausea and rash. Most recovered in one to two weeks, but some could progress to severe illness. 

There was currently no specific treatment for dengue or severe dengue, but early detection and access to proper medical care lowered the probability of death due to severe dengue.

Since the beginning of this year, over five million cases and 5,000 deaths of dengue had been reported worldwide. So far in 2023, close to 80 per cent of the dengue cases, or 4.1 million, had been reported in the Americas, followed by South-East Asia and the Western Pacific.

The distribution of the mosquitoes had changed in the last few years due to several social and environmental factors and in 2023, El Nino phenomena had resulted in increased detection of dengue in previously dengue-free countries.

It was also concerning that dengue outbreaks were occurring in fragile and conflict-affected countries of the Eastern Mediterranean region such as Afghanistan, Pakistan, Sudan, Somalia and Yemen. These countries were facing simultaneously outbreaks of infectious diseases, mass population movements, poor water and sanitation infrastructure and recurring natural disasters. This was also the case in the African region, where evidence of dengue circulation had been detected in local populations and among travellers returning from more than 30 African countries.

Dengue was not endemic in Europe and the majority of cases were usually travel-related, yet this year, limited clusters of autochthonous dengue had also been reported in Italy, France and Spain.

Considering all these factors, WHO assessed the risk of dengue as high globally, which required maximal attention and response from all the levels of the organization. WHO would support countries around the world controlling the current outbreaks and prepare countries to respond to the upcoming dengue season. WHO was currently actively supporting the countries to plan and implement priority multisectoral interventions to control the spread of dengue. These interventions included strengthening surveillance and reporting of cases; conducting risk stratification of countries to prioritise actions; providing support through global expert networks; updating guidance and training for clinical management; strengthening environmental and mosquito surveillance to guide vector control activities and reduce the density of mosquitos; and reinforcing risk communications and community engagement.

WHO was leading the Global Arbovirus Initiative, an integrated strategic plan to tackle emerging and re-emerging arboviruses with epidemic and pandemic potential. The initiative focused on monitoring risk, pandemic prevention, preparedness, detection and response, and building a coalition of partners. 

Countries, partners and the international community needed to work together, be alert and prepared to detect transmission of dengue and other mosquito borne diseases such as Zika and Chikungunya in tropical areas globally and especially the southern hemisphere, where the dengue season was about to start. The general population could lower their risk of dengue by using mosquito repellent to prevent mosquito bites, especially during the day, and eliminating mosquito breeding sites in and around homes.

In response to questions, Dr. Rojas Alvarez said that in the African region, 170,000 cases had been reported this year and about 700 people passed away due to dengue. There had been 15 countries in Africa with reported outbreaks, including Benin, Capo Verde, Chad, Côte d'Ivoire, Ethiopia, Ghana, Guinea, Mali, Nigeria, but Burkina Faso was the most affected, with almost 150,000 cases. Africa had experience with battling mosquito borne diseases such as malaria, but the mosquito that transmitted dengue behaved differently to the one that transmitted malaria, so some methods used to control malaria were not effective in controlling dengue.

An integrated approach using both insecticides and larvicides in water sources was effective in controlling dengue. Mosquitoes lived in any containers that had clean water. Communities needed to be aware of where mosquitos bred and reduce such areas. There were many measures that could be taken to prevent further spread.

In the Americas, the largest number of cases were reported in Brazil, Peru and Mexico, whereas the highest percentages of cases were reported in Caribbean islands. Usually for dengue control, house-to-house visits were conducted by public health officers, who checked for reservoirs where mosquitoes could breed. Such checks could not be carried out during the COVID-19 pandemic. Reduced health care services had impacted the response to several infectious diseases during the pandemic. However, diagnosis techniques developed during the pandemic could be used to better identify dengue cases.

During 2023, Italy reported 82 cases, France 43 and Spain three cases of dengue. This year, there were limited cases of autochthonous transmission, that is, transmission from local mosquitoes, in Europe. This was due to summers getting hotter. The aedes aegypti breed of mosquito that transmitted the virus was established in many areas including Cyprus, Madeira and other regions of Portugal since 2022. Mosquito eggs could hibernate during winter and then hatch when the temperature rose. The current winter was a golden opportunity for Europe to start controlling mosquitoes before dengue could become a real threat.

Climate change increased rainfall and humidity, which created better conditions for mosquitoes carrying the infection to breed and spread. This had led to mosquitoes becoming established in countries where they previously could not, such as in Europe, southern North America and southern areas of Latin America such as Uruguay and Buenos Aires in Argentina. They were now being seen up to 2,000 metres above sea level. Unusual rainfalls had increased mosquito densities in Bangladesh, Oman and Saudi Arabia. Countries like Colombia were seeing mosquitos for the first time in mountain areas, and previously unexposed populations were at risk. There was still a large percentage of the population in African countries like Burkina Faso that might be susceptible, so WHO was conducting prevalence surveys to understand better the real burden of dengue in the African region. This would help it develop better targeted interventions.

Mexico had been hyperendemic for dengue for a few decades. People could be infected with dengue up to four times, and the second infection might lead to severe dengue. This year, there had been almost 230,000 reported cases in Mexico, around 180 cases per 100,000 people. The Pan American Health Organization was coordinating with the WHO country office and the Ministry of Health in Mexico to address the situation with a multi-sectoral plan. Floods and hurricanes were leading to higher mosquito density and transmission.

In North America, there were cases reported in Florida and Puerto Rico, and there was a risk for introduction of dengue in other southern states of the United States, as the aedes aegypti mosquito was already present in some states such as Texas. Action needed to be taken to reduce mosquito densities and the risk of transmission in these states.

About 10 per cent of patients could develop severe symptoms such as bleeding and organ impairment, which could lead to death. Usually, severe symptoms came after fevers came down. It was important to detect warning signs such as intense abdominal pain, persistent vomiting, bleeding in the gums and in the gastrointestinal system, fluid accumulation and drowsiness. Populations needed to be aware to the symptoms and seek medical care when needed. Fluid intake was the main treatment for dengue. Proper fluid intake could prevent dengue symptoms from becoming severe.

There were about 390 million dengue infections per year. Dengue had a less than one per cent case fatality rate, but if there was an outbreak of five million cases, health facilities would become packed and it would be very difficult to provide care for patients. WHO was working to strengthen surveillance of cases to get a better view of the real burden of dengue.

Announcements

Alessandra Vellucci, Director of the United Nations Information Service (UNIS) in Geneva, said this was the last briefing for 2023. UNIS would continue to post updates on news from the United Nations System, and the first briefing for 2024 would be held in hybrid format on 5 January.

The United Nations Secretary-General António Guterres would hold a stakeout briefing at 12:30 p.m. New York time, at which he would address topics including the situation in the Middle East. The briefing could be watched live on UN Web TV.

Some changes were made to access to the Palais des Nations during the closure period of 20 December 2023 to 7 January 2024. During this period, the Palais was accessible from 8 a.m. to 5 p.m. through the Pregny Gate by foot, bike or car, and from 5 p.m. to 8 a.m. and on weekends and official holidays through the Nations Gate by foot (located to the right of the Peace Gate) and the Pregny Gate by car or bike.

Ms. Vellucci wished all a restful holiday period. This was not a time for celebrating as the news was so dire in many parts of the world, but she expressed hope for a brighter and more peaceful 2024.

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The webcast for this briefing is available here: https://bit.ly/unog22122023

The audio for this briefing is available here: https://bit.ly/UNOG22122023