July 13, 2020
Camille Joyce O. Cruzada, MD
Dengue is an endemic disease in the Philippines and a challenge to public health1-4. It was prioritized as the most important mosquito-borne viral disease in the world last 2012 but remained to be the largest arboviral threat to humans17,33 and the world’s fastest growing vector disease12. Despite local efforts, it continued to affect an increasing number of individuals yearly with an incidence rate of 22.4 per 100,000 population and an average annual percentage change of 24.4% in the past 3 decades5-10.
Despite global movements, dengue continued to have an upward trend with an estimated 30-fold increase in incidence within the last 50 years, involving territories previously unaffected by the disease4. With urbanization, environmental destruction, travel and climate change further propagating the expansion and disrupting the usual pattern of the disease1,13,33, it is high time that tools for early detection, disease monitoring, and vector control be developed.
Reflection: The Unclear Status of Dengue Worldwide
Dengue is one of the 17 neglected tropical diseases identified by the World Health Organization (WHO) 4,12. It shares the category with Guinea Worm disease and leishmaniasis, to name a few, which are exclusive to poor communities and are endemic to the tropics and subtropics. These diseases also lack public health attention, receive poor research funding, accomplish little progress in research and development, and have high morbidity, low mortality and no specific treatment in comparison to other infectious diseases12.
Unlike other tropical diseases, dengue has spread to developed countries such as France, Croatia, Portugal and the United States14. It also drew more support with the commemoration of June 15 as ASEAN Dengue Day and the birth of international campaigns such as Break Dengue for worldwide awareness15.
Dengue even became the 4th most funded infectious disease following HIV/AIDS, tuberculosis and malaria in 2012 but the gaps in research and increased private interest in vaccine development decreased global funding and kept dengue in this category12,16. The tunnel vision on vaccines has left little insight on the more pressing issues of vector control, diagnosis and most importantly, disease surveillance9, 12.
Disease surveillance is a long-standing problem of dengue control and prevention1,4,10,18. Without a standard protocol, only as little as 13.2% of actual cases are reported in Southeast Asia, where the disease is endemic26. Records of cases come mostly from the symptomatic, younger population seeking consult in public institutions, some records of cases are lost to misdiagnosis and preference for home care4,18,28-31.
Reports lose quality to lack of laboratory confirmation and inconsistent classification2,4,18,29. Aware of the discrepancy, several countries have created prediction models to correct their records, adding as much as 1-65 cases per documented case depending on disease severity2,10,18-27. Available data was also adjusted based on geographic distribution, revealing the burden of disease to be thrice than what WHO reported17.
Though mechanisms can be used to approximate data, these will yield problematic results without uniformed data from active and passive surveillance32. Unless dengue can be properly identified, reported, clinically diagnosed and laboratory confirmed, the true burden of disease cannot be determined.
Vision: The Roadmap to Prevention
Current local clinical practice guidelines rely on signs and symptoms for the diagnosis and immediate management of dengue34 but the role of laboratory confirmation remains crucial4,34-36. Other than to clinch the definitive diagnosis of a disease with diverse clinical presentation to provide properly timed intervention, it is essential for baseline epidemiological studies, existing policy evaluation, and innovative measures for prevention.
There is an array of diagnostic tests available for detecting dengue but none can detecting dengue in various stages of the infection35, comes the search for an easy, rapid test where sensitivity and specificity are not compromised36.
Peeling et al (2010) identified the ideal dengue diagnostic to be rapid, highly sensitive, and serotype specific; with low diagnostic threshold, high potential for real-time surveillance and most importantly, the ability to distinguish dengue from flavivirus infection with similar presentation.
Other things to consider are the cost, ease of use, portability, storage and stability in the field to be applicable in endemic rural communities. Unfortunately, commonly used tools do not fit these perfectly33,37-39. Viral isolation, though capable of definitive diagnosis, fails to deliver results promptly.
Reverse Transcription Polymerase Chain Reaction (RT-PCR), a senstive and specific test, has decreased usability with the operation of specialized equipment, need for thermal cycling protocol training and lack of center-to-center standardization. Nonstructural protein 1 (NS1) antigen test, despite providing rapid results, suffers from inconsistent sensitivity, with decreased sensitivity observed in secondary infections and those caused by DENV-4.
Antibody serology may be able to differentiate primary from secondary infections, however, it violates the most important criteria for an ideal test by yielding false-positive results in the presence of other flavivirus.
Fortunately, alternatives are proving to be closer to ideal. Immune cross-reactivity and decreased antigenemia during secondary infection were shown to be bypassed by antigen-antibody combination kits35,40-42. Not only do these have higher sensitivity and specificity than the individual tests, they also have detection rates comparable to RT-PCR.
Similarly, most diagnostic weaknesses are addressed by the isothermal cycling detection methods— transcription-mediated amplification (TMA), nucleic acid sequence-based amplification (NASBA), reverse transcription loop-mediated isothermal amplification (RT-LAMP) and reverse transcription recombinase polymerase amplification (RT-RPA)43-48.
The close to 100% sensitivity allows RT-LAMP and RT-RPA to turn positive with as little as 100-1000 RNA copies present and enables TMA to detect the disease in even in RT-PCR negative samples. Their high specificity further allows the former to differentiate flaviviruses accurately and prevent cross-reactivity.
The rapid result production of RT-LAMP and RT-RPA in the absence of thermocycling and easy visualization through immunofluorescence use improves disease surveillance and increases their potential as point-of-care diagnostics. Complete evaluation and validation are the only barriers left for their application in current programs 33,41.
In the Philippines, RT-PCR is the confirmatory test of choice19. Though expensive, it is preferred over the rapid diagnostic kits, which miss the disease 65-68% of the time49. Methods involving sandwich enzyme-linked immunosorbent assay (ELISA) and fluorogenic real time RT-PCR were then explored, and revealed the potential of ELISA as basis for laboratory confirmation50-52.
The continued drive to improve diagnostics pushed for nucleic acid amplification test (NAAT)-LAMP technology to be integrated in the national dengue control and prevention program and gave birth to an affordable novel local diagnostic, Biotek-M™Dengue aqua Kit, within the last 2 years53,54. With these, a cost-effective, accurate, and efficient approach for diagnosis is no longer out of reach.
The road to prevention is still long and winding but we must keep treading the detours to cover the lapses we have neglected for so long. Though unsettling, let us continue to implement, assess, and modify existing vector control procedures and be open to new approaches like vaccination to strengthen our defense against dengue4.
Although tedious, let us go beyond disease detection and fuel the budding research on biomarkers for disease severity and noninvasive monitoring to improve outcomes from the infection33. Moreover, let us develop stricter evaluation and regulation schemes for diagnostics to protect developing and endemic areas from advances of private interests 17. When all these are put in place, it is not too late to uncover dengue’s true burden of disease.
 Bravo L, Roque VG, Brett J, Dizon R, L'Azou M (2014). Epidemiology of dengue disease in the Philippines (2000–2011): a systematic literaturereview. PLoS Negl Trop Dis. 2014;8:e3027.
 Edillo FE, Halasa YA, Largo FM, Erasmo JNV, Amoin NB, Alera MTP, Yoon I-K, Alcantara AC, Shepard DS (2015). Economic cost and burden ofdengue in the Philippines. Am J Trop Med Hyg. 2015;92:360–366.
 Department of Health (2011). National Objectives for Health Philippines, 2011–2016: Health Sector Reform Agenda Mono- graph No. 12. Manila, Republic of the Philippines: Health Pol- icy Development and Planning Bureau (HPDPB), Department of Health.
 World Health Organization (2013). Global Strategy for Dengue and Prevention and Control 2012–2020. Geneva: World Health Organization.
 Department of Health, Republic of the Philippines, National Epidemiology Center (2017). Dengue Morbidity Week Reports (2013-2017). Retrieved June 9, 2019 from https://www.doh.gov.ph/statist...
 Department of Health, Republic of the Philippines, National Epidemiology Center (2019). Dengue Monthly Reports (2018-2019). Retrieved June 9, 2019 from https://www.doh.gov.ph/statist...
 Department of Health, Republic of Philippines National Epidemiology Center (2017) Field Health Service Information System (FHSIS) Annual Reports, 1995– 2017. Retrieved June 9, 2019 from https://www.doh.gov.ph/publica...
 World Health Organization, West Pacific Regional Office (2019). Dengue Situation Updates (2015-2019) Retrieved June 9, 2019 from https://www.who.int/westernpac...
 Agrupis KA, Ylade M, Aldaba J, Lopez AL, Deen J (2019) Trends in dengue research in the Philippines: A systematic review. PLoS Negl Trop Dis 13(4): e0007280. https://doi.org/10.1371/ journal.pntd.0007280
 Wartel TA, Prayitno A, Hadinegoro SR, Capeding MR, Thisyakorn U, Tran NH, et al. (2017). Three Decades of Dengue Surveillance in Five Highly Endemic South East Asian Countries. Asia-Pacific Journal of Public Health29(1):7–16. Epub 2017/02/16. https://doi.org/10.1177/101053... PMID: 28198645.
 Horstick O, Tozan Y, Wilder-Smith A (2015) Reviewing Dengue: Still a Neglected Tropical Disease? PLoS Negl Trop Dis 9(4): e0003632. doi:10.1371/journal.pntd.0003632
 World Health Organization (2019). The Health and Environment Linkages Initiative: Vector-borne disease. Retrieved June 9, 2019 from https://www.who.int/heli/risks...
 Jain, S., & Sharma, S. K. (2017). Challenges & options in dengue prevention & control: A perspective from the 2015 outbreak. The Indian journal of medical research, 145(6), 718–721. doi:10.4103/ijmr.IJMR_1325_16
 The Lancet Infectious Diseases (2014). Neglected tropical diseases: no longer someone else’s problem. doi:10.1016/S1473-3099(14)70928-4
 Break Dengue (2018). A World Dengue Day Retrieved June 12, 2019 from https://www.breakdengue.org/wo...
 Chapman N, Doubell A, Oversteegen L, Chowhadry V, Rugarabamu G, Ong M, & Borri J (2018). Neglected Disease Research and Development: Reaching New Heights. Retreived June 12, 2019 from https://www.policycuresresearc...
 Bhatt S, Gething PW, Brady OJ, Messina JP, Farlow AW, Moyes CL, et al. (2013) The global distribution and burden of dengue. Nature496(7446):504–7
 Undurraga, E. A., Edillo, F. E., Erasmo, J., Alera, M., Yoon, I. K., Largo, F. M., & Shepard, D. S. (2017). Disease Burden of Dengue in the Philippines: Adjusting for Underreporting by Comparing Active and Passive Dengue Surveillance in Punta Princesa, Cebu City. The American journal of tropical medicine and hygiene, 96(4), 887–898. doi:10.4269/ajtmh.16-0488
 Chairulfatah, A, Setiabudi, D, Agoes, R, van Sprundel, M, Colebunders, R. (2001). Hospital based clinical surveillance for dengue haemorrhagic fever in Bandung, Indonesia 1994-1995. Acta Trop.80:111-115.
 Porter, KR, Beckett, CG, Kosasih, H. (2005). Epidemiology of dengue and dengue hemorrhagic fever in a cohort of adults living in Bandung, West Java, Indonesia. Am J Trop Med Hyg.;72:60-66.
 Phuong, HL, de Vries, PJ, Nga, TT. (2006). Dengue as a cause of acute undifferentiated fever in Vietnam. BMC Infect Dis. 6:123.
 Tien, NT, Luxemburger, C, Toan, NT (2010). A prospective cohort study of dengue infection in schoolchildren in Long Xuyen, Viet Nam. Trans R Soc Trop Med Hyg.104:592-600.
 Anderson, KB, Chunsuttiwat, S, Nisalak, A. (2007). Burden of symptomatic dengue infection in children at primary school in Thailand: a prospective study. Lancet369:1452-1459.
 Wichmann, O, Yoon, IK, Vong, S. (2011). Dengue in Thailand and Cambodia: an assessment of the degree of underrecognized disease burden based on reported cases. PLoS Negl Trop Dis.5:e996.
 Endy, TP, Chunsuttiwat, S, Nisalak, A.(2002). Epidemiology of inapparent and symptomatic acute dengue virus infection: a prospective study of primary school children in Kamphaeng Phet, Thailand. Am J Epidemiol. 156:40-51.
 Undurraga, EA, Halasa, YA, Shepard, DS. (2013). Use of expansion factors to estimate the burden of dengue in Southeast Asia: a systematic analysis. PLoS Negl Trop Dis. 7:e2056.
 Nealon, J, Taurel, AF, Capeding, MR. (2015). Symptomatic dengue burden in 5 countries in Asia-Pacific: epidemiological evidence from a dengue vaccine trial. Paper presented at: ASVAC, the 5th Asian Vaccine Conference; Hanoi, Vietnam.
 Diaz-Quijano FA (2015). Dengue severity: a key determinant of underreporting. Tropical Medicine and International Health 20(10):1403 doi:10.1111/tmi.12542
 Shepard DS, Undurraga EA, Betancourt-Cravioto M, Guzmán MG, Halstead SB, Harris E, Mudin RN, Murray KO, Tapia-Conyer R, Gubler DJ. (2014). Approaches to refining estimates of global burden and economics of dengue. PLoS Negl Trop Dis. 8:e3306.
 Cavalcanti, L. P., Braga, D. N., da Silva, L. M., Aguiar, M. G., Castiglioni, M., Silva-Junior, J. U., … Pompeu, M. M. (2016). Postmortem Diagnosis of Dengue as an Epidemiological Surveillance Tool. The American journal of tropical medicine and hygiene, 94(1), 187–192. doi:10.4269/ajtmh.15-0392
 Tomashek KM, Gregory CJ, Rivera Sánchez A, Bartek MA, Garcia Rivera EJ, Hunsperger E, Muñoz-Jordán JL, Sun W. (2012). Dengue deaths in Puerto Rico: lessons learned from the 2007 epidemic. PLoS Negl Trop Dis. 6:e1614.
 Toan NT, Rossi S, Prisco G, Nante N, Viviani S. (2015). Dengue epidemiology in selected endemic countries: factors influencing expansion factors as estimates of underreporting. Trop Med Int Health. 20:840–863.
 Rodriguez-Manzano, J., Chia, P. Y., Yeo, T. W., Holmes, A., Georgiou, P., & Yacoub, S. (2018). Improving Dengue Diagnostics and Management Through Innovative Technology. Current infectious disease reports, 20(8), 25. doi:10.1007/s11908-018-0633-x
 Department of Health, Republic of the Philippines (2011). Revised Dengue Clinical Management Guidelines. National Dengue Prevention and Control Program, National Center for Disease Prevention and Control.
 Muller DA, Depelsenaire ACI, &Young PR. (2017). Clinical and Laboratory Diagnosis of Dengue Virus Infection, The Journal of Infectious Diseases 215(2):S89–S95. doi:10.1093/infdis/jiw649
 World Health Organization (2009). Dengue: Guidelines for Diagnosis, Treatment, Prevention and Control
 Peeling RW, Artsob H, Pelegrino JL, Buchy P, Cardosa MJ, Devi S, et al. (2010). Evaluation of diagnostic tests: dengue. Nat Rev Microbiol. 2010;8(12 Suppl):S30–8
 Dutra, N. R., de Paula, M. B., de Oliveira, M. D., de Oliveira, L. L., & De Paula, S. O. (2009). The laboratorial diagnosis of dengue: applications and implications. Journal of global infectious diseases, 1(1), 38–44. doi:10.4103/0974-777X.52980
 Pang, J., Chia, P. Y., Lye, D. C., & Leo, Y. S. (2017). Progress and Challenges towards Point-of-Care Diagnostic Development for Dengue. Journal of clinical microbiology, 55(12), 3339–3349. doi:10.1128/JCM.00707-17
 Shamala DS (2015). Laboratory Diagnosis of Dengue: A Review. International Medical Journal of Malaysia 14(1)
 Wang, S. M., & Sekaran, S. D. (2010). Early diagnosis of Dengue infection using a commercial Dengue Duo rapid test kit for the detection of NS1, IGM, and IGG. The American journal of tropical medicine and hygiene, 83(3), 690–695. doi:10.4269/ajtmh.2010.10-0117
 Blacksell, S. D., Jarman, R. G., Gibbons, R. V., Tanganuchitcharnchai, A., Mammen, M. P., Jr, Nisalak, A., … Lalloo, D. G. (2012). Comparison of seven commercial antigen and antibody enzyme-linked immunosorbent assays for detection of acute dengue infection. Clinical and vaccine immunology : CVI, 19(5), 804–810. doi:10.1128/CVI.05717-11
 Munoz-Jordan JL, Collins CS, Vergne E, Santiago GA, Petersen L, Sun W, Linnen JM (2009). Highly Sensitive Detection of Dengue Virus Nucleic Acid in Samples from Critically Ill. Journal of Microbiology 47(4) doi: 10.1128/JCM.01564-08
 Gyawali N, & Taylor-Robinson A., (2017). Diagnosis of Dengue: Strengths and Limitations of Current Techniques and Prospects for Future Improvements.
 Sahni, A. K., Grover, N., Sharma, A., Khan, I. D., & Kishore, J. (2013). Reverse transcription loop-mediated isothermal amplification (RT-LAMP) for diagnosis of dengue. Medical journal, Armed Forces India, 69(3), 246–253. doi:10.1016/j.mjafi.2012.07.017
 Hu, S. F., Li, M., Zhong, L. L., Lu, S. M., Liu, Z. X., Pu, J. Y., … Huang, X. (2015). Development of reverse-transcription loop-mediated isothermal amplification assay for rapid detection and differentiation of dengue virus serotypes 1-4. BMC microbiology, 15, 265. doi:10.1186/s12866-015-0595-1
 Abd El Wahed A, Patel P, Faye O, Thaloengsok S, Heidenreich D, Matangkasombut P, et al. (2015). Recombinase Polymerase Amplification Assay for Rapid Diagnostics of Dengue Infection. PLoS ONE 10(6): e0129682. doi:10.1371/journal. pone.0129682
 Teoh B-T, Sam S-S, Tan K-K, Danlami MB, Shu M-H, Johari J, Hooi P-S, Brooks D, Piepenburg O, Nentwich O, Wilder-Smith A, Franco L, Tenorio A, AbuBakar S. (2015). Early detection of dengue virus by use of reverse transcription- recombinase polymerase amplification. J Clin Microbiol 53:830 –837. doi:10.1128/JCM.02648-14.
 Ramos AKA, Mesa-Gaerlan FJC, Quilala PF, Mapua CA, Suarez LAC, Labayo HKM, et al. (2012). Prevalence of dengue infection and accuracy of the rapid dengue-NS1 antigen strip test as a screening tool for dengue infection among patients presenting with fever at the emergency room of St. Luke’s Medical Center (A prospective study). St Luke’s Journal of Medicine8(1):31–8.
 Buerano CC, Natividad FF, Contreras RC, Ibrahim IN, Mangada MN, Hasebe F, et al. (2008). Antigen sand- wich ELISA predicts RT-PCR detection of dengue virus genome in infected culture fluids of Aedes albopictus C6/36 cells. The Southeast Asian journal of tropical medicine and public health 39 (5):817–21. Epub 2008/12/09. PMID: 19058574.
 Buerano CC, Ibrahim IN, Contreras RC, Hasebe F, Matias RR, Natividad FF, et al. (2000). IgM-capture ELISA of serum samples collected from Filipino dengue patients. The Southeast Asian journal of tropical medicine and public health. 31(3):524–9. Epub 2001/04/06. PMID: 11289014.
Tan IL, Dimamay MP, Buerano CC, Alfon JA, Tanig CZ, Matias RR, et al. (2010). Development and evaluation of a fluorogenic real-time RT-PCR for the detection of dengue 3 virus. Journal of medical virology82(12):2053–63. Epub 2010/10/29. https://doi.org/10.1002/jmv.21... PMID: 20981793.
 Research Institute for Tropical Medicine (2018). NAAT-LAMP offers simpler, cheaper diagnosis for dengue. Retreived June 13, 2019 from http://ritm.gov.ph/introducing...
 Philippine Council for Research and Development (2018). Biotek M Dengue Detection Kit. Retrieved June 13, 2019 from http://pchrd.dost.gov.ph/index...