Preparing for the dengue explosion in Kathmandu, Nepal
Authors: Sudeep Adhikari, Buddha Basnyat, Kripa Maharjan
Journal: The Lancet Global Health (2020)

Dengue, a self-limiting viral illness of the tropics, appears to be the infectious disease of the 21st century in many countries because of its heavy disease burden and socioeconomic impact.1Wilder-Smith A Ooi EE Horstick O Wills B Dengue.Lancet. 2019; 393: 350-363Summary Full Text Full Text PDF PubMed Scopus (180) Google Scholar It was first reported in Nepal in the southern plains in 2004. Since then, there have been frequent outbreaks in that region.2Khetan RP Stein DA Chaudhary SK et al.Profile of the 2016 dengue outbreak in Nepal.BMC Res Notes. 2018; 11: 423Crossref PubMed Scopus (11) Google Scholar Kathmandu, the capital of Nepal, which is located higher north of the plains, faced its first outbreak during the monsoon in July, 2019. The city has become an ideal breeding ground for the Aedes vector mosquito because of climate change, relentless and haphazard urbanisation, brisk trade and transit from dengue-infested areas, and poor health infrastructure, all conducive to the spread of dengue.1Wilder-Smith A Ooi EE Horstick O Wills B Dengue.Lancet. 2019; 393: 350-363Summary Full Text Full Text PDF PubMed Scopus (180) Google Scholar, 3Simmons CP Farrar JJ van Vinh Chau N Wills B Dengue.N Engl J Med. 2012; 366: 1423-1432Crossref PubMed Scopus (1060) Google Scholar Aedes mosquitos fly only 500 m in their lives, so have the potential to rapidly spread infection in a closely-packed population.4Verdonschot PF Besse-Lototskaya AA Flight distance of mosquitoes (Culicidae): a metadata analysis to support the management of barrier zones around rewetted and newly constructed wetlands.Limnologica. 2014; 45: 69-79Crossref Scopus (103) Google Scholar Dengue virus has four serotypes. Primary infection with any serotype in a non-immune population generally causes mild disease, such as Kathmandu faced this season. When secondary infection with another serotype occurs in the same population, there is antibody-dependent enhancement, which usually causes severe dengue (plasma leakage, bleeding, and shock).1Wilder-Smith A Ooi EE Horstick O Wills B Dengue.Lancet. 2019; 393: 350-363Summary Full Text Full Text PDF PubMed Scopus (180) Google Scholar, 3Simmons CP Farrar JJ van Vinh Chau N Wills B Dengue.N Engl J Med. 2012; 366: 1423-1432Crossref PubMed Scopus (1060) Google Scholar Over time, this secondary infection might lead to a so-called explosion of the disease, as occurred in Delhi, Dhaka, Ho Chi Minh City, Senegal, and Singapore some years ago,5Guo C Zhou Z Wen Z et al.Global epidemiology of dengue outbreaks in 1990–2015: a systematic review and meta-analysis.Front Cell Infect Microbiol. 2017; 7: 317Crossref PubMed Scopus (126) Google Scholar, 6Ganeshkumar P Murhekar MV Poornima V et al.Dengue infection in India: a systematic review and meta-analysis.PLoS Negl Trop Dis. 2018; 12e0006618Crossref PubMed Scopus (48) Google Scholar with markedly more infection than Kathmandu has recently witnessed. When such an explosion eventually occurs in Kathmandu, disease demographics might change as the dengue virus becomes more endemic, affecting mostly children and young adults,3Simmons CP Farrar JJ van Vinh Chau N Wills B Dengue.N Engl J Med. 2012; 366: 1423-1432Crossref PubMed Scopus (1060) Google Scholar, 6Ganeshkumar P Murhekar MV Poornima V et al.Dengue infection in India: a systematic review and meta-analysis.PLoS Negl Trop Dis. 2018; 12e0006618Crossref PubMed Scopus (48) Google Scholar in contrast to the recent outbreak, in which many older adults were affected. Other problems could abound. Many patients with fever might be incorrectly diagnosed with dengue because of use of commercial rapid diagnostic kits with low specificity. Companies could cash in on the epidemic and produce unreliable tests, as has already started to happen.7Garg A Garg J Singh DV Dhole TN Can rapid dengue diagnostic kits be trusted? A comparative study of commercially available rapid kits for serodiagnosis of dengue fever.J Lab Physicians. 2019; 11: 63Crossref PubMed Google Scholar A tug-of-war might occur between the worried well and the truly sick. Additionally, because dengue is mostly an urban disease, many influential people—including politicians—could be affected, resulting in widespread publicity and confusion, unlike silent epidemics in the Himalayas. Hospitals might be overwhelmed and many needy patients with other diseases could be turned away. Patients who develop WHO-defined warning signs for risk of severe disease might require admission to hospital.8WHODengue: Guidelines for Treatment, Prevention and Control. World Health Organization, Geneva2009Google Scholar However, severe infection occurs in only a small proportion of patients and, if treated properly, mortality is below 1%.1Wilder-Smith A Ooi EE Horstick O Wills B Dengue.Lancet. 2019; 393: 350-363Summary Full Text Full Text PDF PubMed Scopus (180) Google Scholar, 3Simmons CP Farrar JJ van Vinh Chau N Wills B Dengue.N Engl J Med. 2012; 366: 1423-1432Crossref PubMed Scopus (1060) Google Scholar In a dengue explosion scenario, many inexperienced doctors might be anxious because of the high-grade fever and low platelets and leukocytes in the blood, which are present even in mild disease.1Wilder-Smith A Ooi EE Horstick O Wills B Dengue.Lancet. 2019; 393: 350-363Summary Full Text Full Text PDF PubMed Scopus (180) Google Scholar This anxiety could lead to overtreatment, including unnecessary admissions, antibiotics, transfusions, and excessive intravenous fluids. Plasma leakage usually resolves within 48 h and the leaked fluid gets reabsorbed rapidly. Excessive fluid administration will cause volume overload and pulmonary oedema, thus increasing mortality.1Wilder-Smith A Ooi EE Horstick O Wills B Dengue.Lancet. 2019; 393: 350-363Summary Full Text Full Text PDF PubMed Scopus (180) Google Scholar, 3Simmons CP Farrar JJ van Vinh Chau N Wills B Dengue.N Engl J Med. 2012; 366: 1423-1432Crossref PubMed Scopus (1060) Google Scholar Increased mortality has been seen in many previous outbreaks (as high as 25% in south India during 2008),6Ganeshkumar P Murhekar MV Poornima V et al.Dengue infection in India: a systematic review and meta-analysis.PLoS Negl Trop Dis. 2018; 12e0006618Crossref PubMed Scopus (48) Google Scholar which could be due to improper fluid management. Before the explosion occurs, Nepal needs to prepare its health system with an algorithm9Yacoub S Farrar J Dengue.in: Farrar J Hotez P Junghanss T Kang G Lalloo D White N Manson's tropical diseases. Saunders Elsevier, London2014: 162-170Crossref Scopus (4) Google Scholar for proper triaging and offer uniform, evidence-based treatment guidelines, especially for severe dengue. Injudicious fluid administration could be avoided by using a simple bedside haematocrit machine and skilful nursing care.3Simmons CP Farrar JJ van Vinh Chau N Wills B Dengue.N Engl J Med. 2012; 366: 1423-1432Crossref PubMed Scopus (1060) Google Scholar Reassurance with proper, evidence-guided information to decrease anxiety will help reduce the hospital load. Hospitals should determine which commercial serological test to use based on accuracy and WHO guidance.8WHODengue: Guidelines for Treatment, Prevention and Control. World Health Organization, Geneva2009Google Scholar The awareness campaign must start early, by focusing on prevention (vector control). Schools are a good place to start such programmes. Students are good learners and can be taught to effectively use repellents and mosquito nets and get rid of water collections near their homes and schools; students will then spread this information to their parents.10Ibrahim NK Abalkhail B Rady M Al Bar H An educational programme on dengue fever prevention and control for females in Jeddah high schools.East Mediterr Health J. 2009; 15: 1058-1067Crossref PubMed Scopus (13) Google Scholar Random spraying of drains in cities might not help. Perhaps, for now, the focus for clinicians in Kathmandu should be to try to mitigate the impact of an inevitable explosion of dengue in the years to come rather than pathophysiological or treatment studies. Nepal should think ahead by learning lessons from the countries who suffered the onslaught of dengue in the past,5Guo C Zhou Z Wen Z et al.Global epidemiology of dengue outbreaks in 1990–2015: a systematic review and meta-analysis.Front Cell Infect Microbiol. 2017; 7: 317Crossref PubMed Scopus (126) Google Scholar, 6Ganeshkumar P Murhekar MV Poornima V et al.Dengue infection in India: a systematic review and meta-analysis.PLoS Negl Trop Dis. 2018; 12e0006618Crossref PubMed Scopus (48) Google Scholar and apply lessons learnt to effectively combat the disease in future by formulating awareness and treatment strategies before an inevitable major outbreak in cities such as Kathmandu. Nepal would be helping itself and providing a model for many other countries where dengue probably will be a major problem in the years to come. We declare no competing interests.