Dengue likely to increase in Dhaka due to climate change: World Bank

A new World Bank report says dengue is likely to increase in Dhaka as the climatic conditions become more suitable for mosquito-borne diseases, along with respiratory diseases and deteriorating mental health conditions.

The report – Climate Afflictions Report – released on Thursday, found a link between the shifting climatic conditions and the increase in respiratory, waterborne, and mosquito-borne diseases as well as mental health issues.

It also mentioned that weather data between 1976 and 2019 indicate Dhaka has been experiencing falling humidity levels, rising temperatures, and heavier summer rainfall. These together with factors like urbanization are increasing the risk of the spread of dengue in Dhaka city.

“Humidity in the range of 60 to 80 per cent, maximum temperature between 25°C and 35°C, and rainfall between 200-800 mm create ideal conditions for mosquitoes,” the report said.

At the same time, the report also mentioned that an increase in mean humidity and mean temperature increases the probability of having anxiety by 0.3 per cent and 0.8 per cent, respectively. More people suffer from depression during winter. Increase in temperature lowers the probability of depression by 1.6 per cent.

“The weather pattern also affects mental health. Changes in weather can cause mood swings. But, seasonality has a slightly different impact on anxiety than depression. The level of anxiety disorders increases with temperature and humidity,” it said.

“Further, women are at higher risk than men for depression, while men are more susceptible to anxiety,” the report mentioned

The WB report also said respiratory illnesses are likely to increase with rising temperature and humidity.

A 1°C increase in temperature rise increases the likelihood of contracting a respiratory infection by 5.7 percentage points, whereas a 1 per cent increase in humidity hikes the chances of catching a respiratory infection by 1.5 percentage points, it said.

Waterborne diseases like cholera are likely to decrease with rising humidity and temperature. A 1 per cent increase in relative humidity reduces the probability on contracting waterborne illnesses by 1.6 percentage points, whereas a 1°C increase in mean temperature reduces the likelihood of respiratory infections by 4.2 percentage points.

According to the WB report, being situated on the edge of the tropical region, Bangladesh experiences some of the wettest monsoons in the world. During peak monsoon, from June to August, the average monthly mean rainfall has declined by 60 millimeters.

On the other hand, mean monthly rainfall for September and October has increased by 43 millimeters, which indicates that the monsoon period is gradually becoming longer, extending now from March to October. Rising temperature during the winter months coupled with erratic rainfall patterns have eroded the distinct seasonality in Bangladesh.