By Aniruddha Ghosal
On November 8, Sri Lanka’s health ministry warned of a large-scale dengue outbreak, with over 60,000 patients and 80 deaths this year. The past months have also seen Pakistan battle a similar flare-up, with over 45,000 infected and 80 dead. Bangladesh is also facing its worst-ever dengue outbreak since 2000, with more than 92,000 cases reported until early November. India, on the other hand, had reported over 91,000 cases and 82 deaths until October 31.
Health officials in these countries have all pointed at the delayed monsoon — which increases the breeding ground for the dengue virus-carrying Aedes aegypti mosquito — as the prime cause behind the outbreaks. But until recently, the mosquito species was restricted to the tropics. With climate change, its habitat range has increased and increasingly vector-borne diseases are becoming a global problem.
From other countries in Asia to the Americas and Africa, the incidence of vector-borne diseases has largely increased. Often, these diseases are linked to poverty, and poorer individuals are often more at risk because of their social or environmental conditions (for instance, slums are often situated in low-lying areas where breeding sites of mosquitoes proliferate) or because they don’t have access to preventive interventions and services. The challenges are myriad and although the problem of vector-borne diseases and climate change isn’t new, how it manifests in different parts of the world often varies. As do the ways in which governments try to tackle the problem.
Lessons From Lanka
While the incidence of dengue is spreading to new countries, the incidence of other diseases, like malaria, is decreasing at the global scale — but remaining stable or even increasing in specific locations. Sri Lanka, for instance, declared itself free of malaria in 2016, after seven decades of strife against the disease. Dr H.D.B. Herath, former Director, Anti Malaria Campaign of Sri Lanka is often credited as the man behind Sri Lanka’s success. In an interview with News18, he said that the country “really started the control of malaria from 1999”. “In 1999, we had a drastic reduction of malaria from 1999, and then the emphasis was on eliminating the disease. We were mopping it up from the country and ensuring that it couldn’t be reduced,” he said.
This is key for a country like India where the topography and climatic conditions are varied and these diseases are turning up in unexpected corners. Take, for instance, the case of Uttarakhand. A recent study found that increased temperatures since 1990 had resulted in an extension in the window of malarial transmissions, and it also found “evidence of occurrence of malaria cases…in areas hitherto free from malaria.” Ramesh C. Dhiman, one of its authors told News18 that since these insects are cold-blooded, the development of the pathogen in their body was also dependent on temperature. “If the temperature is too low or too high, neither the insect will be able to develop properly nor the pathogen. Some areas which are colder, particularly in Himalayan region, may not be suitable for transmission of a VBD now, because of lower temperature than the required threshold, but with climate change, such areas may become suitable,” he warned.
