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

Bangladesh is currently facing its most severe dengue fever outbreak on record, as hospitals grapple with accommodating patients amidst the rapid spread of the disease in the densely populated nation.

The country’s Ministry of Health and Family Welfare said from January 1 to August 7, 2023, a total of 69,483 laboratory-confirmed dengue cases and 327 related deaths, with a case fatality rate (CFR) of 0.47 percent were reported.

Of these, 63 percent of cases and 62 percent of deaths were reported in July 2023.

The World Health Organisation said although dengue is endemic in Bangladesh, the current surge in the disease is unusual in terms of seasonality and the early sharp increase in comparison to previous years, when the surge started around late June.

The CFR so far this year is relatively high compared to previous years for the full-year period.

The higher incidence of dengue 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.

According to WHO, dengue cases started to rise in May 2023 and the peak is unlikely to have been reached. The reported number of dengue cases this year is the highest compared to the same periods recorded since 2000. The most affected area in the Dhaka division is Dhaka city corporation, accounting for 52.8 percent of cases and 78.9 percent of deaths.

Epidemiology of dengue

It 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 virus (DENV) has four serotypes: DENV-1, DENV-2, DENV-3, DENV-4. Infection with one serotype provides long-term immunity to the homologous serotype but not to the other serotypes; sequential infections with a different serotype put people at greater risk for severe dengue. Many DENV infections produce only mild flu-like illness and over 80 percent of cases are asymptomatic.

There is no specific treatment for dengue. 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 percent.

Dacca fever turns dengue

WHO says dengue was first recorded in the 1960s in Bangladesh (then known as East Pakistan) and was known as “Dacca fever”. Since 2010, cases of dengue appear to coincide with the rainy season from May to September and higher temperatures. Bangladesh’s climate conditions are becoming more favorable for the transmission of dengue 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.

Repurposing of Covid hospitals

Six hospitals assigned for the management of COVID-19 patients in Dhaka city have been repurposed for the treatment of dengue. Dedicated dengue wards and dengue corners have been established in Medical College hospitals. The fourth edition of the National Guideline for Clinical Management of Dengue Syndrome has been updated and instructions given to all Government and Private Hospitals to follow it..

WHO risk assessment

Dengue is endemic in Bangladesh with recurrent outbreaks and is one of the major public health concerns in Bangladesh. Dengue virus has the potential to cause epidemics resulting in high morbidity and mortality. 

The prevention and control of dengue depends on vector control. A dengue vaccine has not been approved in Bangladesh. The dengue risk at the national level is assessed as ‘High’ due to the ongoing rapidly increasing number of cases and deaths with the peak not yet reached. In addition, DENV2 has been identified as the predominant circulating serotype, following four years of DENV3 predominating which may result in higher numbers of severe cases as a result of a second infection with a heterologous serotype.

The very high number of admissions for dengue have put pressure on the healthcare capacity. Bangladesh has three international airports, three seaports and twenty-three land ports. Bangladesh shares 94% of its land border with India with frequent population movement across the land crossing. However, dengue is already endemic in India including the eastern Indian states which share land borders with Bangladesh and where Aedes mosquitoes breed and circulate.

Due to social and economic factors, many people migrate from Bangladesh to other countries thereby increasing the risk of international disease spread. Bangladesh receives a large volume of international tourists, and the possibility of travellers acquiring the disease and contributing to its further spread outside the country cannot be ruled out.

WHO says it promotes a strategic approach known as Integrated Vector Management (IVM) to control mosquito vectors, including Aedes species,. The organization has called for entomological surveillance to assess the breeding potential of Aedes mosquitoes in containers as well as to monitor insecticide resistance to help select the most effective insecticide-based interventions. WHO, however, does not recommend that any general travel or trade restrictions be applied to Bangladesh.

Also read: Not just prevention needed to fight dengue in India.