Dengue Surveillance System: A Proposal

This has been the worst July, August, and September in the history of dengue cases in Bangladesh. With more than 200,000 cases and almost 1,000 deaths till the end of September, it is a full-blown undeclared epidemic. The disease cycle needed to be broken by eliminating the disease source, in this case by vector management. Authorities are applying tools to identify the larva and adult population of Aedes Aegypti but to control such a large-scale outbreak, a smarter surveillance system needs to be designed. Along with it, newly set up rules and regulations for citizens and city corporations will ensure accountability to the law of the land. Any strategy would first require an extensive understanding of the nature of Aedes aegypti mosquito and the time sensitive relationship of the vector to weather which is altering with climate change. A real time surveillance system with a heat map visualization will help identify the locations of the dengue infested areas to take targeted action.

Surveillance Data Generating a Heatmap:

The Directorate General of Health Services (DGHS) is daily publishing an extensive bulletin of total dengue cases, region-wise cases in a day, daily and total deaths, and the admitted patients in different hospitals.¹ This same platform can be made interactive with real time reporting to take faster decisive actions. As the country transitions from Digital to Smart Bangladesh, there are 126.1 million internet users out of which 114 million are mobile internet subscribers and 12.1 million are broadband users, all we have to do is leverage this resource for reporting, informing and viewing purpose.²

For the sake of the citizens- DGHS or the city corporations or the development sector or the private sector- anyone can set up a hotline number or an app or a platform where dengue cases must be tracked in real time. To make matters simpler, even shastho batayon 16263 can be used.³ Dengue positive cases are detected either from the hospitals or from the diagnostic laboratories. Wherever and whenever a case is detected it must be made mandatory to be reported in that call center or in that app with the patient’s particulars and most importantly their current addresses. The system has to be sophisticated to avoid duplication of reporting; hence masked patient information is important. The case positivity and address data will directly feed into a geographical information system (GIS) that creates a heat map for visualizing the locational statistics of the disease infested areas. Once the heat map generates the exact location of the source of disease, the authorities can inspect the areas, find, and clean the reservoirs, calculate 400-meter radius of the areas to intensely destroy not only the mosquitoes but the eggs and the larvae too till the outbreak is under control. Simultaneously short video clips of the eggs, larva and the breeding containers must be widely distributed within communities for general citizens to actively participate in cleaning their surroundings.

There might be limitations of data accuracy as the address itself may not be a true reflection of the actual source of infection since it could have been contracted from school, office, or other marketplaces. But usually, people move around within a radius of a few kilometers in any city and the mosquito bites mostly two hours after dawn and two hours before dusk, by which time people are usually at home.

This heat map will also alert hospitals, pharmacies, and diagnostics in the vicinity to increase resources to manage the outpouring of cases.

Correlation of Aedes aegypti lifecycle, mosquito population and disease outbreak:

The female Aedes aegypti gets infective seven days after biting a dengue positive person and then transmits the virus directly by biting and indirectly by passing the virus down to its eggs. These mosquitoes live close to human habitation with a life span of two weeks, rest indoors in dark areas, and are ankle biters that get attracted to CO2, sweat and heat emanating from the human body. After feeding on human blood, it lays eggs inside of artificial domestic containers. It produces hundreds of eggs in three to five batches at different sites and the eggs are dirty looking, sticky, and can get dried up to survive from nine months to year. They hatch when they get covered with little water to the larval stage, and even the larva can remain in a hibernation state for some time. Before flying off as an adult mosquito, both the larvae and pupae are aquatics and are visible. This whole cycle of hatching to flying takes only seven to ten days but it is weather dependent.⁴ The ideal external temperature for Aedes breeding is 25-29.5°C at 80% humidity. When there is a rise of temperature to 32 °C to 35 °C, the mosquitoes develop faster, the virus within the mosquitos replicate rapidly and the biting rate of the vector becomes higher, which results in swifter disease transmission.⁵ The most important factors regarding control of Aedes is- when the weather is right, the disease outbreak has started and there is a heat map that flags the most devasted areas then a smart targeted and intense vector control management must be executed within 400-meter radius of that area to eliminate the mosquitoes, eggs, and larvae. Why 400 meters? Because unlike other mosquitoes Aedes has a flying range of maximum 400 meters, and in reality, for our densely populated cities it is even less.⁶

Importance of Identifying the dominant variant:

There are four distinct serotypes of the dengue virus. Recovery from infection by one of these four (DEN-1, DEN-2, DEN-3, and DEN-4) provides the infected person with lifelong immunity against that particular strain and cross-immunity for 6-12 months to the other serotypes. If the person is infected by other serotypes subsequently, then the risk of severe dengue increases. The Institute of Epidemiology, Disease Control and Research must duly identify the dominant variant of the season and announce it to help individuals remain aware of what they were struck with. The symptoms of the disease are altering with each passing year; therefore, it is imperative to improvise treatment protocol and share it widely. The use of Eltrombopag Olamine (Eltrom) is indicated in cases of severe thrombocytopaenia and it has delivered positive outcome in Dengue management. It initiates cascading reaction that induces platelet formation from bone marrow progenitor cells.⁶

Stakeholders’ Responsibilities:

In the urban areas mayors of city corporations and councillors from the wards are the elected public representatives. In rural areas, elected members represent the wards, and chairman of the union heads the council of the members. Utilizing these representatives to form vector control committees in defined geographic areas might help as it had done in West Bengal.

Citizens’ participation can be achieved when enough knowledge is transferred by sharing videos, leaflets, text messages with photos of the mosquito, its eggs, its larvae, and the breeding sites via tv, radio and social media. If dengue infested specific zip codes are identified, then people living in those areas must be alerted by text messages to clean up their neighbourhood. A diligent pest control system is needed at the ports to avoid migration of vectors.

More urban planting of marigold, eucalyptus, mint, lemongrass, grapefruit, lavender, and pine trees will help repel mosquitos. Use of mosquito repellents, wearing light coloured loose fitted clothes covering full body, and sleeping under mosquito net will give some protection.

Experimental projects using genetically modified sterile male mosquitoes and the use of Wolbachia bacteria to inhibit the replication of dengue virus within Aedes to suppress dengue transmission have been much in discussion but yet to be executed. It is time that atleast a pilot project is launched.

The horse has bolted, dengue was always more a concern of the metropolitan cities especially Dhaka but this year by September more cases are observed outside Dhaka. It is a health emergency and at this point a GIS surveillance system can help manage this menace in the most cost-effective manner for both short-term and long-term.