DENGUE; Control and Prevention

Dengue fever (DF)/Dengue hemorrhagic fever (DHF)/Dengue shock syndrome (DSS); a mosquito-borne viral disease occurs in approximately 390 million people in more than 128 countries annually. Out of which, around 24% are symptomatic leading to severe infections. Global Dengue virus (DENV) transmission has been accelerated by the human mobilization, urbanization and global warming mainly in tropical and sub-tropical climates because of which the prevalence of disease increases drastically in the recent decade. Dengue is one of the major global health problems listed in tropical neglected diseases. Moreover, till date there is no any cure for dengue; treatment is only limited to rehydration therapy, and with vector control strategies seems to be relatively ineffective and vaccines are under licensing. Hence, the only options to reduce the disease burden are to prevent the infection and control as recommended by WHO. These five technical elements need to be implemented scientifically to avoid transmission and adverse effects from the infections.

1.      Diagnosis and case management:

Over 80% of dengue viral infection is asymptomatic which is not detected by a simple rapid serodiagnostic kit. Most of countries are using those kits in their health care settings and many countries even lack such kits and do diagnosis simply by blood profiling or platelets count. This is one of major problems seen because of which a large carrier population are misdiagnosed. The carriers are the reservoirs of DENV infections and keep on transmitting the infections to new individuals. The situation alarms us for the immediate need of highly sensitive and specific diagnostic kits (IgM capture ELISA, IgG ELISA and RT-qPCR) for proper diagnosis and management of patients which is a key to overcome this situation. Using those kits in each and every health care setting and related clinic for definitive diagnosis will not allow a single case to be undiagnosed. The government, health ministry and authorities are in the front line to fulfill funding gap and regular monitoring for these facilities. Like proper diagnosis, good management of positive cases (patients infected with DENV) needs an equal attention to stop further transmission and to stop severe dengue related complications. Sufficient number of trained staff should be appointed for management and extensive care of cases in all health care facilities. As there is no any specific treatment of DENV infection, the cases are given supportive care and an emergency team of medical officers stand back at any time to treat in case of hemorrhage and shock syndrome. We have to take special precautions for children.

2.      Integrated surveillance and outbreak preparedness

As previously mentioned, a single DENV infection may expand to many cases. Missing of case reporting can be managed by integrated surveillance. Every year DENV is occurring in new regions due to global climate change. Those new cases in the new region lead to outbreaks in the areas and nearby. The surveillance will keep us updated which will be very helpful in control of epidemics and disease outbreaks. The surveillance system should collect data on mobile migrant population, vectors, cases and carriers as well as the tools and techniques used in diagnosis. It should be integrated as a part to national health system. The system is developed in such a systematic way that every single case will be reported to the center level. For the surveillance, mobile data collection tool can be used throughout the system as it can be used by any laboratory technician to high level authorities and will be a fastest tool to update.  In case of any outbreak, the management team will handle, manage possible preventive and control measures. The more quickly the team manage the outbreak, the less chances to spread and the less will be disease burden.

3.      Sustainable vector control

The global warming is an important factor to increase the vector population even in sub-tropical regions. Aedes aegypti is a main vector in DENV transmission followed by A. albopictus as a secondary vector transmitting dengue virus in different regions of world. The potential vectors should be identified with the help of entomologist and through extensive surveillance. For the control of vector and vector breeding, WHO sustainable vector control strategies should be applied wherever possible. Dengue vector mainly take blood meal at day time, so people should be aware to use full lengths clothes and use the repellant while working outside. People in the low-income communities in endemic areas should be provided with insecticidal treated nets and insecticide spray for internal use. They should be strictly aware to protect themselves during day hour working in vulnerable regions such as in agricultural field and in the forest. Most importantly they should be trained on vector control strategies. Access to water and sanitation are very important factors in vector control and elimination such as destroying mosquito breeding sites; stagnant water bodies, removing herbs nearby houses, proper housing, using mosquito traps etc. Without vector control we can’t think about the control of DENV infection hence we should focus on it.

4.      Future vaccine implementation

Few vaccines are under the progress of licensing. Vaccines are an alternative tool to eliminate the dengue infection from the world. However, many of vaccines have antibody dependent enhancement complications. Few vaccines are only effective in dengue seropositive children while few have efficacy in older age groups. These all should be considered before we implement vaccines in the community. We should choose the best one with vaccine efficacy, gather the demographic information of population (age and location) to be vaccinated, prepare the necessaries and cost estimation whether we can cover all the communities or not. Tetravalent live attenuated vaccine, Dengvaxia is one potential vaccine we can use for children.

5.      Basic, operational and implementation research

Besides the above-mentioned strategies, the implementation should be regularly supervised and monitored.  The monitoring will help to identify the limitations of implementation strategies. It is only possible when collaboration from all sectors; government bodies, private sectors, individual’s effort as well as community level efforts will work together. Through collaborative works, extensive researches on available tools and techniques are revised and strengthened, the most suitable kits, tools or vector control strategies are identified in a particular region and also try to find early epidemic indicators which can be used for early warming of potential epidemics and outbreaks.  By implementing these technical elements, we can reduce the disease burden of DENV infection and meet the goal set by WHO.

(Reference:  https://www.who.int/denguecontrol/resources/9789241504034/en/)