Spike in dengue fever cases due to global warming, warns WHO

Global warming that is marked by higher average temperatures, precipitation and longer periods of drought could prompt a record number of dengue fever infections worldwide, the World Health Organization (WHO) warned on Friday.

“About half of the world's population is at risk of dengue, and dengue affects approximately 129 countries,” said Dr Raman Velayudhan, WHO’s Head of the Global Programme on control of Neglected Tropical Diseases. “We estimate that about 100 to 400 million cases are reported every year. This is basically an estimate and the American region alone, for example, has reported about 2.8 million cases and 101,280 deaths.”

Dengue, also called breakbone fever, is the most common viral infection that spreads from mosquitoes to people. Most people with dengue do not have symptoms and recover in one to two weeks. But some people develop severe dengue and need hospital care.

“In some cases, especially when you get the infection for the second time, which we call a secondary infection, this can lead to severe dengue and it can be fatal too,” explained Dr. Velayudhan, briefing journalists at the United Nations in Geneva.

Dengue is spread by the Aedes species of mosquito. The disease is more common in tropical and subtropical climates. Its incidence has grown dramatically worldwide in recent decades, Dr. Velayudhan explained.

“In 2000, we had about half a million cases and today in 2022 we recorded over 4.2 million cases, which really shows an eight-fold increase. And, this can be much higher as we get more and more accurate figures.”

Asia represents around 70 per cent of the global disease burden and the future outlook is bleak, according to the WHO expert. In Europe, the Aedes mosquito is established and dengue and chikungunya infections have been reported for more than a decade.

“European countries are also on alert because Europe had recorded an Aedes transmission of either dengue or chikungunya since 2010,” said Dr. Velayudhan. “We have had more outbreaks since then and it is estimated that the mosquito is present in about 22 European countries.”

Numerous factors in addition to climate change have driven the spread of dengue fever, such as the increased movement of people and goods, urbanization and pressure on water and sanitation.

“The mosquito manages to survive even when there is water scarcity,” said the WHO expert. “So, both during a flood situation as well as a drought situation, dengue can increase. The virus and the vector multiply faster at a higher temperature. This is a well-known fact.”

Dengue fever does not have a specific treatment and there is no direct drug intervention available. Usually, the disease is treated with medicines to treat fever and pain.  

A dengue test takes two to three days to receive a reliable result.  

Several new tools are under development that provide greater hope in preventing and controlling dengue, such as better diagnostics. A few antivirals are undergoing clinical trials.

“Two or three of these candidates are going through Phase Two trials and will move on to Phase Three, which is very promising,” Dr. Velayudhan said. “There is also one dengue vaccine in the market, which has got certain limitations, and two other candidates are actually in the pipeline and are under review.”

The UN health agency stresses that prevention is key. Because the mosquito bites during the day, it is important that people protect themselves at home, in schools and at work by spraying repellent around buildings.

Other protective measures include mosquito coils and sleeping under nets.

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1. Exterior medium shot: UN Palais with flags
2. Wide shot: moderator behind podium and attendees at the press conference, screens with speakers on both sides of the podium
3. SOUNDBITE (English) – Dr Raman Velayudhan, WHO Unit Head Global Program on control of Neglected Tropical Diseases coordinating dengue and arbovirus initiative: “About half of the world's population is at risk of dengue, and dengue affects approximately 129 countries. We estimate that about 100 to 400 million cases are reported every year. This is basically an estimate. And the American region alone, for example, has reported about 2.8 million cases and 101’280 deaths.”
4. Wide shot: moderator behind podium and attendees at the press conference, screen with speakers on the side
5. SOUNDBITE (English) – Dr Raman Velayudhan, WHO Unit Head Global Program on control of Neglected Tropical Diseases coordinating dengue and arbovirus initiative: “In some cases, especially when you get the infection for the second time, which we call a secondary infection, this can lead to severe dengue and it can be fatal too.”
6. Medium shot: attendees in the foreground, screen with speakers in the background
7. SOUNDBITE (English) – Dr Raman Velayudhan, WHO Unit Head Global Program on control of Neglected Tropical Diseases coordinating dengue and arbovirus initiative: “In 2000 we had about half a million cases and today in 2022 we recorded over 4.2 million cases, which really shows an eight fold increase. And actually this can be much higher as we get more and more accurate figures.”
8. Medium shot: moderator behind podium and attendee at the press conference, screen with speakers on the side
9. SOUNDBITE (English) – Dr Raman Velayudhan, WHO Unit Head Global Program on control of Neglected Tropical Diseases coordinating dengue and arbovirus initiative: “The European countries are also on alert because Europe had recorded an Aedes transmission of either dengue or chikungunya since 2010. We have had more outbreaks since then and it is estimated that the mosquito is present in about 22 European countries.”
10. Medium shot: moderator behind podium at the press conference
11. SOUNDBITE (English) – Dr Raman Velayudhan, WHO Unit Head Global Program on control of Neglected Tropical Diseases coordinating dengue and arbovirus initiative: “Also the high precipitation, increased temperature and even the mosquito manages to survive even when there is water scarcity. So both during a flood situation as well as a drought situation, dengue can increase. The virus and the vector multiplies faster at a higher temperature. This is a well-known fact.”
12. Medium shot: attendee in the foreground, screen with speakers in the background
13. SOUNDBITE (English) – Dr Raman Velayudhan, WHO Unit Head Global Program on control of Neglected Tropical Diseases coordinating dengue and arbovirus initiative: “There are very few antiviral research working on, and actually two or three of these candidates are going through phase 2 trials and will move on to phase 3, which is very promising. There is also one dengue vaccine in the market, which has got certain limitations, and two other candidates are actually in the pipeline and are under review.”
14. Close shot: attendee taking a picture of the press conference
15. Close shot: attendee typing 
16. Medium shot: moderator