History of dengue
Dengue is described by the World Health Organization (n.d.) as a fast emerging pandemic viral disease with worldwide prevalence. The viral disease was initially traced to the epidemics in Java and in Egypt in 1779. Some literatures trace back the virus and its vectorsto the Chin Dynasty. It was hypothesized that the disease occured in the Western hemisphere in the midddle of the 17th century and believed to originate from tropical America. However, some researchers would point out that the accounts of dengue outbreaks were traced back during the 18th and 19th century in Southeast Asia.The dengue outbreaks in the tropical and subtropical areas across all continents were extensive during teh 19th and 20th centuries. The epidemics extend across other subcontinents and islands in the Caribean and South Pacific regions (Schlesinger, 1977).
The global dengue epidemics was also caused by the expansion of the global shipping industry in the 18th and 19th centuries that enhanced the spread of the principal mosquito vector to new geographic areas.Moreover, the major epidemics with its severe and fatal form of dengue called the dengue haemorrhagic fever (DHF) happened first in the Southeast Asia.Gubler (2006) ascribed this epidemic as caused by the unplanned urbanization in tropical developing countries, globalization and the lack of effective mosquito control.Dengue has become one of the most serious infectious diseases that affect the tropical urban areas.The impact of dengue in the global community is significant, but there is some difficulty in ascertaining the actual data of the prevalence and incidence of the disease due to the inadequate disease surveillance, underreporting of its incidence and misdiagnosis.
Dengue epidemiology
The dengue epidemics can result in massive outbreaks, such as one that occured in Athens and Pireus where about 80% of the population were affected.The prevalence of dengue outbreaks is expected to expand further due to the dynamics of climate change, changes in socioeconomics, globalization, travel and the evolution of the dengue virus.The dengue virus currently has no cure. There is no vaccine available and the disease cannot be treated by any specific antiviral medication. This fact alone can contribute to the growing threat and incidence of dengue worldwide.The incidence of dengue is expected to increase 30 fold across geographic borders with expansions to new countries affecting both the urban and rural areas.
The annual incidence of dengue infection is estimated to reach 50 million of cases. The historical patterns of spread of the dengue virus continue to grow. In 2000, the epidemic spread to new areas with increasing incidence to those regions already affected. In 2003 new countries reported incidence of the dengue virus for the first time.It was in 2005 when the high cases of fatal incidence of the dengue outbreak occured in Timor Leste.The fatality rate of dengue infection in India, Indonesia and Myanmar is about 3 to 5 percent and only 1 percent across the other regions. The highest on record of dengue cases was reported in 2007 that occured in Indonesia.Dengue outbreaks in America occured in a cyclical manner, usually every 3 to 5 years. The most commonly affected regions are the Caribbean and Central and South America. The highest reported cases of dengue outbreak was in 2002 in America due to the lack of vector surveillance and control measures (World Health Organization, 2009).
The main cause of vector transmission for the dengue virus are the Aedes Aegypti and Aedes Albopictus.The Aedes Aegypti is known to be the main arthropod vector for the transmission of majority of dengue outbreaks.These mosquitoes are highly active on daylight and they predominantly spread across both tropics and subtropic regions.The transmission of the virus is made between people through the mosquito bite. Prevalent in Indonesia, Philippines and Pacific Islands are the transmission of the virus through the Aedes albopicus and Aedes polynesiensis as common vectors of dengue.The dengue outbreaks in the African region shows evidence that it is increasing in size and in frequency. However due to poor surveillance data, dengue reports are not reliable in this region. The reports on dengue outbreaks are often extracted from laboratory confirmation.The origin of the Aedes Aegypti as the primary vector of the dengue virus is traced back to Asia and Africa. They became widespread across regions and transcends geographic boundaries due to the commercial expansions and shipping vessels with humans as the breeding site of the virus. This process allows for the slow but persistent spread of the virus across coastal destinations.
Currently, the Centers For Disease Control and Prevention (2014) reported that the global pandemic of dengue accounts to affect about 40% of the world's population with about 2.4 billions of individuals at risk of dengue transmission. The most serious form of dengue infection is dengue hemorrhagic fever (DHF) that accounts to 500,000 cases worldwide and about 22,000 cases of reported deaths annually with children as the most common victims.The dengue fever is now known to be the most important arthropod-borne viral disease in humans in terms of the mortality and morbidity rates (Kurstak, Marusyk, Murphy and Regenmortel, 1990).
Dengue prevention
The main focus of the Global Strategy for Dengue Prevention and Control is sustainable vector control. This appears to be the most effective preventive method against dengue morbidity and mortality rate by 2020 considering the lack of vaccines against the dengue virus. The World Health Organization advocates the strategic method of Integrated Vector Management which was described to be the most cost effective and rational process of dengue vector control (Murray, Quam and Smith, 2013).There is no vaccine or chemoprophylaxis that are available for dengue infection. This makes anyone living or travelling to dengue endemic areas highly susceptible to getting the condition. The Centers for Disease Control and Prevention advocates preventive measures like using insect repellent, wearing protective clothes with covering on the legs and arms and to find an accommodation with screened windows for travelers. The local community should also cover any standing water which are common breeding sites for mosquitos (Tomashek, Sharp and Margolis, 2015).
The main goals and objectives of World Health Organization in its global strategy for dengue prevention and control includes reducing the dengue mortality rate by 50% and morbidity rate by 25% by 2020. According to the World Health Organization, the preventive measures against dengue mortality include the implementation of timely and appropriate clinical management of the condition.This process involves an early clinical diagnosis of the condition, hospital reorganization, intravenous rehydration, and clinical staff training. In the primary and secondary care levels for dengue, which are the stages where the patients are first evaluated, an efficient front line response is necessary in order to prevent hospital admissions.
Because dengue is a global health problem, preventive measures across national and international levels must be implemented. The advocacy of the WHO is to implement programs with international collaboration and the harmonization of the regional efforts through strong leadership from the health care workers. A successful clinical outcome is possible with early diagnosis of the infections and through the implementation of an accurate differential diagnosis and a quick laboratory assessment and confirmation of the disease. Emphasized is the need for training of both the medical and non-medical staff who are involved in dengue control to have optimal dengue case management. As part of the dengue prevention program, a surveillance system for dengue should also become part of the national health information system (World Health Organization, 2012).
The National Institute of Health (NIH) provides for the prevention program against dengue which includes the use of precautionary measures from being bitten by mosquitoes. It advocates the use of mosquito repellent and the wearing of protective clothing. The National Institute of Allergy and Infectious Disease (NIAID) of the National Institutes of Health (NIH) of the US Department of Health and Human Services are currently funding several dengue research projects that seek to discover the best prevention measure agaist the dengue infection and in the development of a new vaccine against dengue. The Dengue vaccine is currently on the third phase of its clinical trial in Brazil (National Institute of Health, 2016). The development of a vaccine is considered to be the most effective weapon against infectious diseases, such as dengue, according to Healthy People 2020 (2014). The advocacy of developing a vaccine against dengue is in line with the Healthy People 2020 objectives in the prevention of the spread of infectious diseases.
Among the important prevention programs against dengue conducted by the World Health Organization include the strengthening of the epidemiological surveillance of dengue, enhancing laboratory networks, strengthening the vector monitoring and control, improve clinical management of patients and strengthen social communications (World Health Organization and Pan American Health Organization, 2014). The Healthy People 2020 advocates the prevention and treatment of infectious diseases such as dengue within the clinical and community levels using evidence based practices. Therawiwat, et al (2005) indicated that the levels of prevention for dengue and its worse form called the dengue hemorrhagic fever in the community should begin within the sub-district health level within villages that are at risk to dengue outbreaks.
Community dengue prevention and control programs include long term and integrated community based mosquito control with the responsibility being shared between the central government and health ministries to the community members. Access to health care facilities are also an important preventive and control measure against dengue. Immediate diagnosis and medical intervention can prevent the morbidity and mortality rate from dengue. Since no vaccine and treatment is available to eradicate the disease, the World HealthOrganization and the CDC advocate environmental management and modification to prevent mosquitoes from gaining access to egg laying habitats. Other preventive measures include cleaning and covering domestic water storage or containers on a regular basis, use of insecticides, using personal household protection such as screening the doors and windows to prevent entrance of daylight biting mosquitoes, and enhancing the community participation for a sustainable vector control. The Healthy People 2020 objective includes the eradication of the burden of infectious diseases in the community and the health care settings and these preventive measures and control are currently the best approach against global dengue outbreaks.
References:
Centers For Disease Control and Prevention (2014). Dengue epidemiology. Atlanta, GA: Centers For Disease Control and Prevention.
Gubler, D.J. (2006). Dengue/dengue haemorrhagic fever: HIstory and current status. Novartis Found Symp. 277:3-16.
Healthy People 2020 (2014). Easy Access Project Eases Immigrants into a New Life – A CDC Preventive Health and Health Services Block Grant Success Story. Healthy People. Retrieved from https://www.healthypeople.gov/2020/healthy-people-in-action/story/easy-access-project-eases-immigrants-new-life-%E2%80%93-cdc-preventive.
Kurstak, E., Marusyk, R.G., Murphy, F.A. and Regenmortel, M.H.V. (1990). Virus variability, epidemiology and control. New York: Springer Science Business Media.
Murray, N., Quam, M.B. and Smith, A. (2013). Epidemiology of dengue: past, present and future prospects. Clin Epidemiol. 5: 299–309.
National Institute of Health (2016). Dengue Vaccine Enters Phase 3 Trial in Brazil. Retrieved from https://www.niaid.nih.gov/news/newsreleases/2016/Pages/DengueBrazilTrial.aspx.
Schlesinger, R.W. (1977). Dengue viruses. New York: Springer-Verlag.
Therawiwat, M. et al. (2005).Community-based approach for prevention and control of dengue hemorrhagic fever in Kanchanaburi Province, Thailand. Southeast Asian Journal Tropical Medicine Public Health. 36(6):1439-49.
Tomashek, K.M., Sharp, T.M. and Margolis, H.S. (2015). Dengue. Centers for Disease Control and Prevention. Retrieved from http://wwwnc.cdc.gov/travel/yellowbook/2016/infectious-diseases-related-to-travel/dengue.
World Health Organization (n.d.). Dengue. World Health Organization. Retrieved from http://www.who.int/denguecontrol/en/.
World Health Organization (2009). Dengue guidelines for diagnosis, treatment, prevention and control. France: World Health Organization.
World Health Organization (2012). Global strategy or dengue prevention and control 2012-2020. France: World Health Organization.
World Health Organization and Pan American Health Organization (2014). State of the art in the prevention and control of dengue in the Americas. Washington, D.C: WHO.
