From 1 January to 7 August 2023, the Ministry of Health and Family Welfare of Bangladesh reported a total of 69 483 laboratory-confirmed Dengue Fever cases and 327 related deaths, with a case fatality rate of 0.47%, according to a press release issued by the World Health Organization on 11 August 2023. Of these, 63% of cases and 62% of the deaths were reported in the month of July 2023. Although dengue is endemic in Bangladesh, the current Dengue Fever surge is unusual in terms of seasonality and the early sharp increase in comparison to previous years, where the surge started around -late June. The case fatality rate so far this year is relatively high compared to previous years for the full-year period. The pre-monsoon Aedes survey shows that the density of Mosquitoes, and the number of potential hotspots is at the highest level in the past five years.
The higher incidence of Dengue Fever is taking place in the context of an unusual episodic amount of rainfall, combined with high temperatures and high humidity, which have resulted in an increased Mosquito population throughout Bangladesh.
Between 1 January and 7 August 2023, a total of 69 483 Dengue Fever cases including 327 related deaths (a case fatality rate of 0.47%) were reported by the Ministry of Health and Family Welfare. As of 30 June 2023, a total of 7978 cases and 47 deaths were reported, however, the cases started surging rapidly from late June and in the month of July alone 63% of cases (43 854) and 62% of deaths (204) were reported.
The number of cases and deaths are higher compared to similar periods in the past five years. Dengue Fever cases started to rise in May 2023 and have been continuing since then, and the peak is unlikely to have been reached. The reported number of Dengue Fever cases this year is the highest compared to the same periods recorded since 2000.
Cases have been reported from all 64 districts of Bangladesh. Cases in Dhaka Division started to increase in epidemic week 17 (23-29 April 2023) and in all eight divisions since epidemic week 26 (25 June to 1 July 2023). The most affected area in the Dhaka Division is Dhaka City, accounting for 52.8% of cases and 78.9% of deaths. Other affected divisions include Chattogram Division (13.2% of cases and 9.2% of deaths), Dhaka Division excluding Dhaka City (11.6% of cases and 2.8% of deaths), and Barisal Division (10.5% of cases and 4.3% of deaths). The Sylhet Division has the lowest number of cases (560) and no deaths reported so far.
As of 7 August 2023, the reported case fatality rate is 0.47%, which is higher compared to previous years. The overall case fatality rate is higher in females than in males (0.72% compared to 0.32%) with females having four times higher case fatality rate than males among those aged 21-40 years (0.71% compared to 0.18%). The older age group recorded a higher case fatality rate compared to the younger age group (1.87% in the age group over 60 years compared to 0.74% in the age group between 41 to 60 years and 0.34% in those aged 40 years and below).
Dengue is a Viral infection transmitted to humans through the bite of infected Mosquitoes and is found in tropical and sub-tropical climates worldwide, mostly in urban and semi-urban areas. The primary vectors that transmit the disease are Aedes aegypti mosquitoes and, to a lesser extent, Aedes albopictus.
Dengue Fever is caused by a Positive Single-strand RNA Virus of the Flaviviridae family and there are four distinct, but closely related, serotypes of the Virus that cause Dengue Fever (Dengue Fever Virus-1, Dengue Fever Virus-2, Dengue Fever Virus-3 and Dengue Fever Virus-4). Recovery from infection is believed to provide lifelong immunity against that serotype. However, cross-immunity to the other serotypes after recovery is only partial, and temporary. Subsequent infections (secondary infection) by other serotypes increase the risk of developing Severe Dengue Fever.
Dengue Fever Virus-2 was the predominant circulating serotype in Bangladesh until 2018, when it was replaced by Dengue Fever Virus-3, which has remained the predominant serotype since 2019. However, Dengue Fever Virus-2 has been identified as the primary circulating serotype in the 2023 outbreak, and this may result in more severe Dengue Fever infections and hospitalizations as a result of a second infection with a heterologous (similar but not identical) serotype. Of the 66 serotyped samples in the month of June 2023, Dengue Fever Virus-2 comprised 51.5% of cases and Dengue Fever Virus-2 comprised 43.9%.
There is no specific treatment for Dengue Fever; however, the timely detection of cases, identifying any warning signs of severe dengue infection, and appropriate case management are key elements of care to lower case fatality rates to less than 1%.
Dengue Fever was first recorded in the 1960s in Bangladesh (then known as East Pakistan) and was known as 'Dacca Fever'. Since 2010 cases of Dengue Fever have appeared to coincide with the rainy season from May to September and higher temperatures. Bangladesh’s climate conditions are becoming more favourable for the transmission of Dengue Fever and other vector-borne diseases including Malaria and Chikungunya Virus due to excessive rainfall, waterlogging, flooding, rise in temperature and the unusual shifts in the country’s traditional seasons.
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