Dengue fever explained: From disease spread to prevention | News

narrator: This is the dengue virus. You may not even realize that you are infected now. However, symptoms can range from high fever to severe headache and vomiting. Or in the most extreme cases, it can lead to death.

After the hottest year on record in 2023, there was an alarming spread of dengue fever. Last year, there were at least 3.5 million infections across Latin America and the Caribbean, with Jamaica seeing 10 times the number the year before. Bangladesh has experienced its worst year for infectious diseases. And Peru's health minister resigned in the face of the country's worst outbreak.

The thing is, 2023 is not surprising. Over the past 20 years, reports of dengue fever have increased tenfold. Approximately half of the world's population is currently at risk. So, what is the real cause of the increase in dengue fever?

Well, it's complicated. There are many interrelated factors. Everything from access to vaccines to perhaps the latest El Niño phenomenon. But it can still be traced back to the main spreaders of the disease. Aedes mosquito. in particular, egyptian temple and Aedes albopictus.

These two tiny species are common culprits in spreading dengue fever, along with other viruses such as chikungunya, Zika, and yellow fever. His body and legs are covered in stripes and he bites throughout the day, easily transmitting the virus from person to person. These mosquitoes primarily lived in forests in tropical and subtropical regions, living in small crevices such as tree holds. They can now be found on every continent except Antarctica, thriving just as well in towns and cities as in rural settings. So why did it spread so quickly?

Well, we humans are helping. A combination of increased international travel and urbanization is allowing disease-carrying mosquitoes to reach more places. And they adapted very well to their new urban residence. Aedes Mosquitoes can lay eggs in water tanks, buckets, bottle caps, and even pet drinking bowls. Basically anything that holds water. They are also increasingly resistant to insecticides, making them harder to repel and kill.And because egyptian temple and Aedes albopictus Because they are active during the day, common interventions such as bed nets are not effective.

Of course, there are other factors at play. climate change.

Dr. Felipe Colon Gonzalez: Countries with suitable climatic conditions, especially in tropical and subtropical regions, have a higher risk of emerging infectious diseases. Aedes Mosquitoes and dengue fever.

narrator: This is Dr. Felipe Colon Gonzalez, Wellcome's technology leader.

Dr. Felipe Colon Gonzalez: For example, Southeast Asia is the highest risk globally. Increasing temperatures increase climate suitability and geographic range. Aedes This spread could lead to mosquito populations and the introduction or establishment of dengue fever in areas of the world where the disease or mosquitoes were previously absent or sporadic.

narrator: Look at Europe. Changes in temperature and rainfall patterns are affecting animal behavior. Aedes Mosquitoes are already moving further north and west across the continent. Now, the number in the region has increased to nearly three times his number. Aedes albopictus It's completely established compared to 10 years ago.

Dr. Felipe Colon Gonzalez: Changes in rainfall due to excessive or limited rainfall can affect water storage practices, for example. When people start storing or collecting more water, it creates opportunities for mosquitoes to breed.

narrator: more Aedes Mosquitoes mean an increased chance of transmission of the dengue virus. In 2022 alone, as many locally transmitted dengue cases were reported in Europe as in the previous 10 years combined. Last year, in 2023, this number increased further, reaching at least 128 cases. But it's not just about broad reach. They also stay longer. Sometimes for several months. Bangladesh experienced exactly this. The climate here is becoming increasingly climatic. Aedes Mosquitoes breed. Over time, dengue fever epidemics became longer and more intense.

Dr. Felipe Colon Gonzalez: When temperatures exceed 16 degrees Celsius, mosquitoes become more likely to transmit diseases. However, this relationship with temperature is not linear. This means that as temperatures rise, infection rates increase. However, if it increases too much, it will start decreasing again. In other words, there is an inverted U-shaped relationship with temperature. The same can be said about precipitation and rainfall.

narrator: Dengue fever is now endemic in more than 100 countries because these mosquito species can spread the virus to new areas. And millions more people will be at risk of dengue fever by the end of this century.

Thankfully, researchers and teams are working diligently to provide a solution. Like Dr. Sophie Jacob, who is based in Vietnam.

Dr. Sophie Jacob: Dengue control programs have primarily focused on vector control. But I don't think this is working. Therefore, new ways to control dengue fever are needed. This includes improving surveillance systems and the need for comprehensive vaccination programs as well as treatment strategies. There is currently no cure, antiviral drug, or host-directed therapy for dengue fever.

narrator: Early warning systems play a key role in combating the rise in dengue fever, as disease outbreaks can be reduced with sufficient advance notice. However, although many early warning systems for infectious diseases have been proposed, the transition from theory to reality is rare. However, there are projects around the world that aim to improve this.

Dr. Sophie Jacob: We just started a project called DART. This is a dengue fever prediction tool that started out as a dengue fever altitude response tool. This is not only an early warning system for public health agencies, but also one of the first to alert the public.

narrator: Tools like this are critical as we continue to live with dengue. Yes, 2023 was a violent year, but this year is likely to be even worse in many parts of the world. Like South America. In the first weeks of 2024, the number of dengue cases in Brazil's capital had already exceeded the number of cases in all of 2023. And if we don't slow global warming, the risk of infection will only increase. We need to act faster.

Modeling suggests that reducing emissions, for example, could significantly reduce infections in the future. These efforts, combined with further research, vaccine development, innovative mosquito control, and increased disease surveillance, will ultimately help slow the spread and protect billions of people from dengue fever.