A sudden surge of dengue at the onset of winter in Chattogram has added a new dimension to the public health crisis. At a time when the number of patients should have been declining, especially after the monsoon, the wave of infections that began in September has become even more severe throughout October and November.
In these three months alone, dengue has been detected in nearly two-thirds of all patients suffering from fever. According to doctors, the concept of seasonal dengue has been shattered. And this is due to climate change, unplanned urbanisation, and the adaptive capacity of the Aedes mosquito.
An analysis of the trend over the last four years shows that from January to November of this year, a total of 4,388 people were infected with dengue in Chattogram. Among them, 935 were infected in September, 990 in October, and 883 in November, ie, 2,808 people were infected in just three months, which is equal to 64% of the total infections.
Statistics from the same period in previous years are also concerning: In 2024, 907 people were infected in September, 1,430 in October, and 1,028 in November; the total number of infected that year was 4,323.
Chattogram’s Civil Surgeon Dr Jahangir Alam said, “The spread of dengue persists even at this time of the year. Many people are getting infected with dengue every day. The rate of dengue infection is higher in some specific areas. Dengue and Chikungunya are both mosquito-borne diseases. To be protected from these diseases, mosquitoes must be eliminated.”
In his research paper titled “Climate, Urbanisation and Governance: Bangladesh’s triple dengue challenge”, Professor Kabirul Bashar of Jahangirnagar University’s Department of Entomology says that the country’s winter is no longer as cold as it once was.
The average winter temperature hovers around 18 to 22 degrees Celsius, which is favourable for the survival and reproduction of the Aedes mosquito. Previously, when the temperature dropped below 15 degrees Celsius, the Aedes mosquito would become close to inactive. Now, due to climate change, their tolerance for heat has also increased.
And while their growth slows down somewhat at lower temperatures, it does not come to a complete stop. He further adds that the heat from urban concrete and transportation systems has created a microclimate, which he terms an “urban heat island”. This prevents temperatures from dropping too low on winter nights, and various open drains and stored water sources remain relatively warm.
As a result, the water where Aedes mosquito eggs are deposited remains active even during the winter months.
Meanwhile, the Chattogram City Corporation (CCC) has launched a Double Crash Programme to eradicate mosquitoes. CCC’s Chief Cleaning Officer Captain Ikhtiar Uddin Ahmed Chowdhury told TIMES of Bangladesh that, starting next week, the most expensive larvicide, BTI (Bacillus thuringiensis israelensis), will be used to kill mosquitoes.
