Over 1,000 people in the east Asian nation of Bangladesh have died from dengue fever, more than four times the number than in the whole of 2022. With at least 209,000 confirmed infections, this year’s outbreak of dengue fever is the worst in the country’s history. At least 112 children were reported amongst the victims, and around one-third of this year’s cases are in young people under the age of 20.
Dengue is quite common in parts of Asia during the June-to-September monsoon (rainy) season as mosquitoes lay their eggs in stagnant water. But this year’s explosive outbreak has left hospitals across the country struggling to find space for new patients, with all 64 of the country’s districts reporting cases. The majority of hospitalized patients this year are suffering from their second or third case of dengue fever. It is well-known that repeated infections lead to more severe symptoms and a greater risk of death.
With so many cases, some officials in Bangladesh say that a “climate crisis” that saw the capital experiencing record-high temperatures this summer followed by an especially wet start to the monsoon season are to blame. Others say that inadequate mosquito control campaigns in rural areas contributed to this year’s outbreak, while some healthcare officials have noted that this year’s strain is more virulent than usual. Meanwhile, the mayor of a suburb of Dhaka has said that the failure of government agencies to remove garbage and stagnant water from their premises is partly to blame for the explosive number of cases in the capital.
Unusual virulence
Although dengue fever is endemic to tropical and subtropical regions of Asia (including Bangladesh,), epidemics such as this year’s are very unusual as most outbreaks crest and then fade away within a matter of days.
In a timely move, the World Health Organization has just begun recommending a brand-new vaccine for dengue fever. Developed by Japan’s Takeda Pharmaceuticals (and sold under the brand name Qdenga), the dengue vaccine is targeted at children aged six to 16. Currently, officials in Bangladesh are working with the manufacturer in order to get the vaccine approved. Qdenga is already approved for use in the European Union, Britain, Brazil, Argentina, Indonesia, and Thailand.
Just before the outbreak began this year, the Larner College of Medicine at the University of Vermont, in conjunction with the International Centre for Diarrhoeal Disease Research (Bangladesh), ran a dengue fever vaccine trial in the country with 192 volunteers that showed the vaccine to be “well-tolerated.”
“This vaccine is the only single-dose tetravalent dengue vaccine, which is an important feature of this vaccine,” said Beth Kirkpatrick, the University of Vermont team leader on the dengue vaccine trial ongoing in Bangladesh.
Dengue cases on the rise globally
Conversely, attempts to devise a reliable test for dengue fever in Bangladesh have largely failed, with only 34.5% of infected patients having a positive PCR test for the disease in a recent study conducted by the Society for Medical Virologists in Bangladesh (SMVB).
“The negative results of the [dengue fever PCR] test make many people think that they do not have dengue, but they later suffer from complications related to dengue. In such cases, it isn’t always possible for the doctors to save the patient,” said SVMB in a press statement.
Partly complicating efforts to detect and treat the disease is the presence of four different variants (known as Den-1, Den-2, Den-3, and Den-4). According to the WHO, half of the world’s population is “at risk” of contracting dengue fever, and there are now more than 400 million infections occurring annually, up from just half a million in the year 2000. Approximately 70% of cases occur in Asia (including Bangladesh), but the WHO has warned that explosive outbreaks are now spreading to new areas of the globe such as Europe.
This summer, authorities in Paris fumigated the city against mosquitos, partly as an effort to control dengue fever outbreaks in France as last year saw more dengue cases in Europe than in the entirety of the previous decade. Although the total of 71 locally-acquired cases in Europe in 2022 pales in comparison to the epidemic now devastating Bangladesh, it points to signs that mosquito-borne illnesses (which include malaria, chikungunya, and Zika) are now spreading into regions of the world outside the warm and wet tropics.
See also: Dengue virus cases on the rise. Global warming among main causes
Dengue as well as other mosquito-borne illnesses are classified as “neglected tropical diseases” (NTDs) because they primarily affect low-income countries in the Global South. But with the confirmation of cases of dengue and other related diseases in Europe and the United States, big pharmaceutical companies are now increasing their funding for research into products to combat these illnesses.
Emphasis on combating dengue fever outbreaks is in the form of prevention, primarily by eliminating the habitats of mosquitoes (stagnant bodies of water) or by spraying insecticides to reduce mosquito population numbers. People living or traveling in areas that are at risk for mosquito-borne illnesses are advised to wear clothing that fully covers the skin, apply insect repellent, and to use mosquito netting when resting.
