As dengue flirts with becoming the next global viral emergency, here’s what to know about the disease, its cause, and why it remains one of the most challenging viruses for scientists to study and control.
A Deadly Disease with an Expanding Territory
Dengue is a viral disease that spreads to humans through the bite of infected mosquitoes. Dengue symptoms include high fever, headaches, nausea, rash, and severe body pain — which is why it is also often referred to as break-bone fever. People that get sick with dengue can have varying symptoms and the disease severity can range from mild to life-threatening. One in twenty people who get sick develop its life-threatening form, severe dengue — a medical emergency that can result in internal bleeding, and even death.
“Over half of the world’s population is currently at risk of infection, and the number of dengue cases has spiked dramatically in recent years.” – Liana Kafetzopoulou
Dengue is the most widespread and rapidly increasing mosquito-transmitted disease in the world. Over half of the world’s population is currently at risk of infection, and the number of dengue cases has spiked dramatically in recent years, with the WHO estimating that 100–400 million infections occur each year.
The rise and spread of dengue are made worse by climate change, human mobility, urbanization, and population growth. These factors not only raise dengue risk in the areas that are already affected, but also help the mosquitoes that transmit the virus to establish themselves in new regions. In recent years, dengue has crossed new borders into European and Eastern Mediterranean regions, exposing even more people to risk of infection.
Limited Prevention and No Treatment
Vaccines are one of the most powerful tools against global viral threats. For a rapidly spreading virus like dengue, an effective vaccine could make all the difference. Progress has been made in the past: several vaccines against dengue have been developed. Two vaccines are currently licensed, yet they both have limitations. The first available vaccine can only be used in individuals who already had dengue in the past, as it can increase the risk of severe dengue in people who haven’t been previously infected. The second, newer vaccine holds great promise, but it is not yet clear if it will be as effective as the world needs it to be.
The most effective way to lower the risk of getting dengue is to protect yourself from mosquito bites. Wearing loose clothes, using mosquito repellants, and sleeping under a mosquito net are all effective measures. Another way to prevent dengue infections is to reduce the number of mosquitoes by eliminating their breeding sites. Mosquitoes that spread dengue like to breed in collections of standing water (inside and outside). A good way to stop mosquitoes laying their eggs near human habitations is to regularly empty, clean and cover such water storage containers around the house, for example buckets or flowerpots.
“There is still no specific treatment for dengue.” – Liana Kafetzopoulou
Unfortunately, there is still no specific treatment for dengue. No antiviral drug exists, and patient care can only focus on pain and fever management, maintaining fluid balance and monitoring for warning signs of severe disease requiring hospitalization.
One Disease, Four Viruses
Dengue researchers face many challenges in developing treatments, creating effective prevention measures, and understanding how the disease progresses in different patients. One reason it is so difficult is the complexity of dengue itself. Dengue is not actually caused by one virus, but rather four closely related yet different viruses, named Dengue virus 1, 2, 3 and 4.
“If you’ve already had dengue once, and you’re infected with a different dengue virus, you have an increased risk of developing severe dengue.” – Liana Kafetzopoulou
People can get infected with dengue multiple times in their life. Generally, once you have been infected with one dengue type, you are subsequently protected against that type, but not against the other three viruses. If you’ve already had dengue once, and you’re infected with a different dengue virus, you have an increased risk of developing severe dengue. This is a problem, as the four dengue types are now co-circulating in the same locations.
To make matters worse, researchers have recently noticed that reinfection can sometimes occur with the same dengue type as well, challenging our existing knowledge and further complicating our understanding of dengue.
A Need for Global Research and Action
Despite decades of research, we still don’t fully understand how the four dengue viruses cause disease. This lack of knowledge has made it difficult to create dengue vaccines that are safe, effective, and universally applicable. Globally, we need to invest more into dengue research, to decipher its complexity and develop effective treatments and preventative measures.
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As our world grows more connected through travel and trade, and as the climate continues to change, dengue viruses gain new opportunities to spread and establish themselves across the globe. Half a century ago, dengue was confined to less than ten countries in the tropics. Today, the four dengue types already circulate in over a hundred countries and continue to spread to new regions.
With its continuous expansion, dengue is no longer only a problem in the tropics — it is a global threat. The time to act is now: to strengthen surveillance, invest in research, and work collectively to control mosquitoes and the viruses they carry.
Written by Liana Kafetzopoulou for the SciMingo Popular Science Writing Course.
