Climate crisis, year-long dengue cases in Delhi linked: South MCD

Delhi: 29 March, 2022 (Hindustan Times)

The weekly vector-borne disease report issued by the three municipal corporations on Monday showed that the city has reported a record 55 dengue cases till March 26 this year, which is almost 5-10 times the normal.

 

The adult aedes aegypti mosquito becomes less active in the open environments as the temperature drops below 20 degrees Celsius (°C) and gradually becomes inactive as the mercury level falls below the 10°C mark.

Linking the rise in dengue cases to the climate crisis, the South Delhi Municipal Corporation (SDMC) commissioner Gyanesh Bharti, who heads the special task force on dengue constituted as per a Delhi high court order, has asked all public and private institutions, government offices, educational institutes and agencies to appoint a nodal officer to ensure their premises do not allow mosquito breeding conditions.

The weekly vector-borne disease report issued by the three municipal corporations on Monday showed that the city has reported a record 55 dengue cases till March 26 this year, which is almost 5-10 times the normal. In the corresponding period, the city had seen only six dengue cases in 2021, 2020 and 2019, and 10 cases in 2018.

“...the unpredictable climate change is now leading to emergence and occurrence of vector borne diseases round the year... This year reports regarding high density of mosquito breeding in coolers, overhead tanks, drums and construction sites have started coming from various localities,” said the communication by Bharti on March 17, which added that the season for vector-borne diseases has started in Delhi.

 

The adult aedes aegypti mosquito becomes less active in the open environments as the temperature drops below 20 degrees Celsius (°C) and gradually becomes inactive as the mercury level falls below the 10°C mark. Temperature in the Capital has almost touched 40°C now.

Noting that educational institutions are opening since Covid-19 cases have come down, the SDMC commissioner issued a list of directions for nodal officers, including orders to ensure there is no water stagnation on the grounds and roofs, and overhead tanks are emptied, cleaned and locked.

A senior public health official said the extreme weather events due to climate crisis and spread of the disease are interlinked. “With an early rise in temperature, people have started using desert coolers and storing water in jerry cans earlier than usual which is leading to ideal breeding sites for the aedes aegypti mosquito which breeds in clear water. The extended rainy season last year and unusual rain in January also added to the problem. There is no vaccine for the mosquito-borne disease. The most effective tool to control the disease is to prevent mosquito breeding sites. The extreme weather events disturb these environmental factors,” a senior municipal public health official said.

There has been a rise in mosquito breeding sites found in houses this year. The action taken report of the three civic bodies shows that the domestic breeding checking staff have found 3,921 cases of mosquito larvae in houses till March 26 this year, as against 1,023 cases in 2021, 389 in 2020 and 1,676 in 2019. The corporations have issued 5,850 legal notices for allowing mosquitogenic conditions this year.

A North MCD public health official said that deputy health officers have also been directed to carry out mapping of all nursing homes and hospitals to improve reporting of dengue cases. Dengue was declared as a notifiable disease under the Epidemic Act in October last year. “All big and small healthcare outlets where fever patients are being treated will be mapped and linked to Integrated health information portal where they will report all new dengue cases,” the official said.

Experts have underlined the need to ensure drives against mosquitoes are carried out all through the year.

Dr BK Tripathi, professor in the department of medicine at Safdarjung Hospital, said dengue cases used to flatten out during extreme summer and peak winters but the mosquitoes are adapting now. “Dengue cases are directly linked to environmental conditions in which breeding takes place. A few years ago, we used to see that the cases were observed after monsoon in September, October season. In peak summer and winter time, the breeding stopped and the cases were not seen but the change in climatic conditions is also happening now with cases reported all through the year,” he said.

Dr Sanjay Rai, professor at the Centre for Community Medicine at All India Institute of Medical Science (AIIMS) said that the focus should remain on preventing mosquito breeding sites.

“Our lifestyle changes are also contributing to the prevalence of these diseases all through the year. The mosquito doesn’t survive in extreme hot or extreme cold conditions but the conditions in our houses are modified for example with the usage of air conditioners. The lifestyle changes create the conditions suitable for breeding,” he said.

He added that it is too early to link it to climate crisis and said more evidence is required to establish the link.