Dengue Fever: A Threat to Billions
Updated: Aug 30, 2020
By Nicole Liang, Morgantown High School, Morgantown, WV
Dengue fever, labeled by the WHO as the most critical mosquito-borne disease in the world, is a prevalent global issue. 40% of the world’s population, roughly 3 billion people, are at risk of contracting dengue. It infects up to 390 million people annually: a 30-fold increase over the past 50 years. The virus, DENV, has four serotypes, meaning one person could potentially be infected four separate times (World Mosquito Program, 2020). While the disease usually causes flu-like symptoms, a variation called severe dengue claims about 20% of those infected. Around 25,000 deaths are reported world-wide annually (WHO, 2019).
The virus’s potent vector, infected mosquitos of the Aedes genus, facilitate its global presence. The Aedes mosquitos are usually found in urban habitats, breed in manmade containers, and their eggs can survive for months without water; thus, they are in close proximity with dense populations, and their numbers are difficult to control. The mosquitos have impressive cold tolerance, and they can migrate through international trade. With these traits, it’s no wonder that these mosquitos are able to proliferate across continents (WHO, 2020).
Dengue fever is common in tropical and subtropical regions of the world, usually in urban or semi-urban areas. However, the disease can spread to wherever the Aedes mosquitos are. Its pervasiveness usually depends on the mosquito population. Higher populations, and higher rates of infection, occur in areas with higher ambient temperatures, precipitation, and humidity. Epidemics tend to be periodic but can vary with the seasons. (Hosangadi, 2019).
The virus has a weeklong incubation period, and symptoms last 3-10 days. Dengue’s most common symptom is fever, accompanied by nausea/vomiting, rash, and aches and pains.
Severe dengue, which occurs in 1 in 20 people infected, is much more serious. If one were previously infected with dengue, the subsequent infection is more likely to result in severe dengue. Symptoms usually arise 24-48 hours after a fever, and include stomach pain, bleeding from the nose/gums, and vomiting blood. Severe dengue can result in shock, internal bleeding, and death (CDC, 2020).
Dengue is endemic is now in approximately 129 countries, with Asia and the Americas having sustained epidemics. The Americas reported 3.1 million cases in 2019, and the Philippines alone had 420,000 cases. 2016 had similar numbers, with 2.38 million cases in the Americas; Brazil contributed to 1.5 million of those (WHO,2020). 2019 had the largest number of global dengue cases recorded, and the virus started to encroach upon previously uninfected countries, such as Afghanistan. A 2014 study by the UPMC Center for Health Security suggests the economic impact of dengue globally was approximately $39.3 billion in 2011, with about 50-65% related to productivity losses (CR,2014). Even into 2020, dengue continues to affect millions. Increases in the number of reported cases occurred in countries such as Bangladesh, Brazil, India, Indonesia, Singapore, and Thailand (WHO, 2020).
The WHO’s Dengue Control Strategy consists of furthering research and providing support to member countries experiencing dengue epidemics through technical or financial means. Country offices work with federal governments to strengthen vector control measures to limit the spread. For example, the Pan American Health Organization and the Western Pacific Regional Office engage in beneficial practices: eliminating mosquito breeding sites, training local health professionals, preparing hospitals to effectively treat severe dengue, and providing resources to the community (protective clothing, insecticide, window screens). The WHO also implements the Global Vector Control Response and creates new protocols for “…surveillance, case management, diagnosis, dengue prevention and control for Member States.” The aim is to halve the number of deaths by 2020’s end (WHO scales up response to worldwide surge in dengue, 2019).
An additional measure for dengue control is a vaccine. Developed in 2015, Dengvaxia was shown to be effective and safe for use in clinical trials. However, a 2017 study revealed that previously uninfected trial participants were more likely to develop severe dengue upon their first infection. The WHO believes that the vaccine can be implemented as part of an “integrated dengue prevention and control strategy” but should be used in conjunction with other practices. The target demographic is 9-45-year-olds in endemic areas who have contracted the virus before. While Dengvaxia must continue to undergo testing, it has shown promise in preventing the prevalence of infection. The vaccine has been licensed for usage in approximately 20 countries (Hosangadi, 2019).
While there is no silver bullet for stopping dengue’s spread, sustained, intense collaboration between governments and researchers reveal new pathways that may one day be the key to defeating this virus once and for all.
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