Dengue Dynamics: A Global Update

Abstract

Dengue viral infection is caused by the dengue virus (DENV), which belongs to the Flaviviridae family of minuscule enwrapped viruses with ribonucleic acid genomes (all the genetic material in an organism),[1] of ‘9000–13,000 bases’.[2] Globally, dengue is the most prevalent vector-borne viral disease, affecting a projected 50–100 million populaces and with, on average 10,000 dengue-related mortality per year.[3] DENV has four serotypes: DENV-1, -2, -3 and -4.[4,5] The presentation of dengue fever is undifferentiated from other viral diseases, ranging from asymptomatic to severe forms.[6] The incubation period to express the symptoms is 4–10 days; however, asymptomatic cases are outnumbered.[7] The World Health Organization (WHO) has categorised dengue into (i) dengue having no warning signs, (ii) dengue having threatening signs and (iii) appalling dengue.[8] The critical warning signs and symptoms of dengue are pain in the abdomen, vomiting, fluid overload, mucosal bleeding manifestations such as epistaxis, gum bleeding, upper gastrointestinal bleeding, lethargy, restlessness, enlarged liver of >2 cm, increased haematocrit and reduced platelet.[9-11] In severe dengue, there is severe plasma leakage with shock and fluid accumulating respiratory problems, severe haemorrhage and organ failure.[12,13] Patients with a history of previous infection with DENV of different serotypes are at greater risk of transforming to severe secondary dengue.[14-16] According to the WHO, the fatality rate for severe dengue is 1% when diagnosed promptly and received proper therapeutic intervention.[17] One more study revealed that the death rate for grievous dengue was 3%–4% of all dengue viral infections and 2%–5% when adequately received medical intervention.[18] However, multiple studies reported that the death rate could increase up to 20%–50% if it remains untreated.[18,19] Simultaneous coinfection with other microorganisms intensifies the disease and can result in the patient’s death, especially in paediatric cases with multiple organ failure.[20-23] Virological tests make diagnosis of dengue, specifically real-time reverse transcription polymerase chain reaction (RT-PCR) assays, dengue immunoglobulin (Ig) M and IgG antibody test by enzyme-linked immunosorbent assay (ELISA) and the non-structural protein-1 ELISA-based antigen assay.[24-28] Treatment of dengue mainly involves giving supportive care to the patient.[29,30] However, intravenous fluid and electrolyte resuscitation are vital in severe cases of plasma leakage.[31,32] FACTORS AFFECTING THE VIRUS TRANSMISSION DENV transmission to humans is mainly through mosquito bites of infected female Aedes aegypti and Aedes albopictus mosquitoes [Figure 1].[33] This mosquito lives primarily in tropical and subtropical temperate countries.[34] The larva stages of the mosquitoes are found in water-filled areas such as artificial water containers at or near human residences and mostly indoor water collections.[35,36] Virus transmission depends on environmental and climate factors, host–pathogen interactions and immunity.[37,38] The DENV transmission is favoured by rapid urbanisation and increased human population movement.[39,40]Figure 1: The transmission of dengue from mosquito to human. This figure has been drawn with the premium version of BioRender (https://biorender.com/ accessed on 1 December 2023) with the license number XP265SYELC. Image credit: Susmita Sinha.Moreover, globalisation, global warming, climatic change and environmental deterioration, including social and human behavioural factors, facilitate the transmission of viruses and circulate to new geographical areas [Figure 2].[41] Low-and-middle-income countries having rapid urbanisation with dense residents, poor quality of health services and climatic suitability for vector growth favour dengue transmission.[42] The higher number of international travellers worldwide expedites the transmission of the viruses to newer places.[43]Figure 2: The factors affecting the dengue virus transmission. This figure has been drawn with the premium version of BioRender (https://biorender.com/ accessed on 1 December 2023) with the license number QX265T1GZN. Image credit: Susmita Sinha.EPIDEMIOLOGY OF DENGUE FEVER Dengue has posed a significant public health problem globally over the last 10 years through its emergence and re-emergence.[44,45] About 50% of the global population is at risk of contracting dengue fever.[46] A 30-fold upsurge in dengue infection has been reported during the last 50 years, including new places worldwide in urban and rural locales.[17,47] One model estimation reported 390 million cases of dengue fever globally,[5,48] and around 22,000 deaths/year.[49-51]Circa 40%–50% of the global population (2.5 billion) reside in dengue-endemic areas.[7,52,53] Dengue endemicity encompasses over 100–128 countries around the globe, especially in South-east Asia (SEA), Eastern Mediterranean, Western Pacific, Africa and America, with an estimated 390 million new cases annually.[5,52,54] The dengue burden in Asia, Africa and America is 70%, 16% and 14%, respectively.[49] Globally, dengue infection rose by 85.47% from 30.67 to 56.88 million from 1990 to 2019.[45] Dengue spreads to new countries such as Italy, France, Croatia, Austria, Spain, Slovakia, Bulgaria, the Netherlands, Belgium, Norway, Poland, the USA, Afghanistan, Benin, Côte d’Ivoire, Tanzania, the Democratic Republic of the Congo, Burkina Faso and Angola.[55-57] CURRENT GLOBAL DENGUE STATUS It is reported that from 2023 to November, more than 4.5 million dengue infections and more than 4000 deaths due to dengue took place in 80 countries across the globe.[58] South and SEA countries have suffered more than other regions.[54,59] In SEA and the Western Pacific Region, around 1.8 billion people are at risk of dengue, almost 75% of the worldwide dengue burden.[7,60] In the SEA, 1.3 billion people reside in 10 countries with dengue endemic.[61] Statistics from 2015 to 2019 showed a 46% increment (from 451,442 to 658,301) in dengue cases and a 2% decrease in mortality (from 1584 to 1555) in these countries.[61] One study on global dengue infection between 1990 and 2019 reported a growth rate of 269.06%, 72.95% and 57.65% in East Asia, South Asia and SEA, respectively.[45] In South Asia, the countries endemic for dengue are Bangladesh, India, Pakistan, Nepal, Sri Lanka and Maldives.[62] The East Asian countries of China, Japan and Korea and SEA countries of Malaysia, Singapore, Indonesia, Myanmar, Thailand, Laos, Cambodia, Vietnam and the Philippines suffer the most.[45,63-65] Almost 60% of all global dengue cases occur in India and China.[45] In 2023, Bangladesh faced an unusual dengue outbreak in 5 years, with a considerable increase in hospitalisation rate.[42,66,67] 296,665 positive dengue cases, including 1520 deaths, were reported from 1 January 2023 till 15 November 2023, with a case fatality ratio of 0.5%.[68] The highest number of monthly dengue infections (79,598 cases) and deaths (396 deaths) took place in September 2023.[60,68] Thailand has reported 119,465 cases with 122 deaths from January 2023 to 25 October 2023, which is higher than previous years’ reports of 2018–2022.[60] In Nepal, from January to October 2023, 42,270 cases of dengue, including 20 confirmed deaths [Case fatality rate (CFR)=0.05%], were reported.[60] Sri Lanka reported 66,476 dengue cases until October 2023, 1.1 times higher than the 61,492 cases reported until week 42 in 2022.[60] Maldives reported 2707 cases from January to September 2023, 75% higher than in 2022 (1548 cases for the same period).[60] In India, till 17 September 2023, 94,198 patients and 91 deaths were reported.[69] Malaysia reports a 103% increment in dengue cases in 2023 compared to 2022. Statistics showed that by 26 October 2023, the total reported cases were 94,181, compared to 47,686 for the same period in 2022, and the number of death cases was 67, compared to 28 for the same period in 2022.[70] Cambodia reports 23,940 cases with 39 deaths till October 2023 compared to 8293 cases and 15 deaths for the same period in 2022.[70] However, Singapore, the Philippines and Vietnam have reported a decrease in dengue cases compared to the previous year. Singapore reports 7885 cases till 15 October 2023 compared to 28,882 cases for the same period in 2022. The Philippines reports 149,129 cases till 7 October 2023, compared to 216,475, which is 31% lower. Vietnam says 113,962 cases till 15 October 2023 compared to 264,078 cases for the same period in 2022, which is a decrease of 56.8%.[70] Although dengue endemicity is not seen in mainland Europe, still dengue cases are demonstrated as sporadic events since 2010 through infected travellers. Viremic travellers from endemic countries cause these autochthonous outbreaks, mainly in four European countries: Croatia, France, Italy and Spain.[71] In 2023, the European Centre for Disease Prevention and Control reported dengue cases in France and Italy as 43 and 76 cases, respectively, from July to October 2023, while in Spain, there were only three cases from August to October 2023.[72] The most endemic regions in America are South America, Central America and the Caribbean. Since the beginning of 2023, a significant outbreak has been reported in the WHO Region of America. Most of the dengue cases in 2023 were found in Brazil, Peru and Bolivia.[73] The total number of cases in America accounts for 3,708,524, including 6124 severe cases with 1796 deaths till October 2023. The highest number of dengue infections took place in the Southern Cone (2,700,916), Andean sub-region (518,605) and Central America (445,980). At the same time, Latin Caribbean, non-Latin Caribbean and North America have reported 14536, 21409 and 944 cases, respectively. The dengue incidence rate in 2023 increased to 582.14/100,000 from 211.99/100,000 in 2009.[74] In Africa, dengue intimidates health equally[57] of financial and workforce liabilities in public health services.[75] Dengue is found to be endemic in 34 African countries.[57,76,77] The Ministry of Public Health and Prevention in Chad, on 15 August 2023, declared a dengue viral fever epidemic had started. There were 1342 and 41 probable and laboratory cases, respectively, by 1 October 2023. One verified case of a dengue patient passed away.[78] Ethiopia reported a dengue outbreak in 2023. Statistics showed that till 10 May 2023, there were 1638, 103 and 9 suspected, confirmed cases and deaths, respectively. The case-fatality ratio is 0.5%.[79] In Mauritius, the dengue outbreak started in June 2023, and 147 cases were reported as of 7 July 2023. The Ivory Coast officially reported the dengue outbreak of 107 cases between 19 June 2023 and 25 June 2023. Twenty-two patients were confirmed by rapid diagnostic tests and RT-PCR and had no mortality.[79] STRATEGY FOR PREVENTION OF DENGUE The most promising dengue prevention and control method is an effective vector control measure for the DENV.[5] The best preventive measures to control dengue are eliminating mosquito breeding areas by spraying insecticide, cleaning, draining stagnant water outside the house and storing household water. The risk factors are the breeding areas, such as static water collections near hospitals, construction sites or densely populated human habitation. They should be emphasised more in addition to all other breeding areas.[66,80] The mosquitoes are usually more active and bite during the daytime, mostly at dusk and dawn. Awareness of the population about this timing is necessary to take measures to prevent biting. Using mosquito repellents on the skin surface and wearing full-sleeved shirts and long pants help control mosquito bites.[81] The use of bed nets, preferably insecticide-treated during sleeping, mainly by the affected person, is an effective method to prevent mosquito bites.[66,82] It is suggested that installing long-lasting insecticidal net curtains draped at mosquito entry points, such as doors and windows, can decrease adult Aedes aegypti mosquitoes significantly. However, care must be taken to keep the curtains hung.[83] Population awareness is necessary to control dengue outbreaks.[18] Vaccination is the most effective way to prevent and restrain the global dengue landscape.[84] An increase in dengue cases has been reported in recent years worldwide, causing a life-threatening burden to people. Awareness and prevention control measures are crucial for the control of dengue outbreaks. Measures for preventing mosquito bites, eliminating mosquito breeding areas and administering effective vaccination are most required for effective management of dengue outbreaks. Consent for publication The author reviewed and approved the final version and has agreed to be accountable for all aspects of the work, including any accuracy or integrity issues. Disclosure The author declares that they do not have any financial involvement or affiliations with any organisation, association or entity directly or indirectly with the subject matter or materials presented in this article. This includes honoraria, expert testimony, employment, ownership of stocks or options, patents or grants received or pending royalties. Data availability Information for this editorial is taken from freely available sources. Authorship contribution All authors contributed significantly to the work, whether in the conception, design, utilisation, collection, analysis and interpretation of data or all these areas. They also participated in the article’s drafting, revision or critical review, gave their final approval for the version that would be published, decided on the journal to which the paper would be submitted and made the responsible decision to be held accountable for all aspects of the work.

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