On November 8, Sri Lanka’s health ministry reported a large-scale dengue outbreak, with more than 60,000 reported infections and 80 deaths since the start of 2019. The past few months have also seen Pakistan battle a similar flare-up, with over 45,000 infections and 80 fatalities. Bangladesh is also facing its worst-ever dengue outbreak since 2000, with more than 92,000 cases reported as of early November. By October 31, India had reported over 91,000 cases and 82 deaths.
Health officials in these countries have all pointed to the delayed monsoon — which increases the breeding grounds for the dengue virus-carrying Aedes aegypti mosquito — as the prime cause behind the outbreaks. Until recently, the mosquito species was restricted to the tropics. But with climate change, its habitat range has increased, and vector-borne diseases are now appearing in places where they hadn't previously been seen.
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 - slums, for instance, 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 (VBDs) 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 Sri Lanka
While 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 fighting against the disease.
Dr H.D.B. Herath, former director of Sri Lanka's Anti-Malaria Campaign, is often credited as the man behind the country's success eradicating the disease. In an interview with News18, he said that Sri Lanka really started to control malaria from 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,” he said.
Sri Lanka's example 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 have resulted in an extension in the window of malarial transmissions. It also found “evidence of the occurrence of malaria cases…in areas hitherto free from malaria.”
Ramesh C. Dhiman, one of the study's 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 the 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.
Herath added that after Sri Lanka's caseload became manageable, the country began attending to each and every case individually to prevent the spread of the disease to other patients. But apart from this, Herath said that they also began separating the local cases, from those that were imported.
“This was done so that we could monitor the local cases and ensure that those went down and also ensure that the imported cases [didn't] give malaria to the locals,” he said. Now Sri Lanka is constantly on the lookout for accidental cases and it takes “blood sacks” as proxy. “All blood donors are screened for malaria…approximately 300,000 people are screened annually. Pregnant mothers are also checked,” Herath added.
While monitoring cases similarly in India might be untenable, officials admitted that migration was a key factor, about which they knew little.
“Each time, we have a dengue outbreak in Cuttack in Odisha…it is immediately after a similar dengue [outbreak] in Kolkata in West Bengal. The two cities are linked via trade and disease,” said an official of the National Vector Borne Disease Control Programme (NVBDCP) in Bhubaneswar.
Government responses to a global problem
China, meanwhile, hasn’t seen a single indigenous case of malaria since August 2016 — an incredible feat considering the country has seen an estimated 30 million cases of malaria since the 1940s and has also seen 300,000 deaths. China had set itself the target of eliminating malaria by 2020. Following this, 13 ministries — including those representing health, education, finance, research and science, development, public security, defense, commerce and industry — joined hands to end malaria.
“This is the only way to go about it. Vector-borne diseases aren’t just a problem for the health department. Why shouldn’t other ministries join in? What about the forest department, or the education department, or the social welfare department,” the official from NVBDCP warned.
China has also implemented a strict and highly effective surveillance strategy that identifies and stops malaria rapidly before the cases can be spread. Known as “1-3-7,” it hinges on timelines that need to be followed to the hour. On day 1, any malaria cases must be reported; on day 3, the Centre for Disease Control and Prevention has to confirm, investigate and determine the risk; and on day 7, it will take measures to ensure that there is no further spread, such as by testing other members of the community for the disease.
Dhiman argued that the “only shortcoming” in India’s routine surveillance for detection of malarial cases, “is that all the cases treated by private practitioners are not taken into account. The surveillance system needs to be strengthened to address the issue of actual burden.”
With the goal of malaria elimination, and with cases dropping in different regions, complacency could set in, he added.
“Therefore, an early warning system to detect outbreaks is very much needed, said Dhiman, noting that the National Institute of Malaria Research where he works as a scientist is making headway in developing such a system.
Increasingly, though, governments are reacting to changes in weather and issuing public health alerts. For instance, in Laos — where, as per reports, over 37,000 people have been infected with dengue — the government earlier in 2019 referred to its weather forecasts while issuing public health alerts.
This measure has been replicated elsewhere, where the health departments are increasingly working in tandem with the meteorological departments to better predict potential crises. In Delhi, for instance, an official told News18, “The health department rolls out a summer plan, a monsoon plan, and a winter plan. The emphasis is to work in tandem and be able to give people the right information at the right time.”
Dr. Kaushik Sarkar of the international nonprofit Malaria No More warned against giving climate change too much importance.
“Climate change should not be used an excuse,” he said, adding that it was a “factor” — but doesn’t change the ground realities of controlling vector-borne diseases. “Yes, the vector-borne disease will increase…these are complex diseases and this is one component, a single agent within the chain of transmission,” he said.
This is Part 4 of a four-part series examining how climate change is impacting the spread of deadly diseases in India. The complete interactive package first appeared on News 18 on 30 Dec. 2019. Each piece was produced with the support of Internews’ Earth Journalism Network.
- Chapter 1: How climate change has altered the rules of Odisha's battle against vector-borne diseases
- Chapter 2: How the fight against malaria reached a fever pitch in Odisha
- Chapter 3: Breaking the cycle of malaria and malnutrition in eastern India
Banner image: A mosquito repellant fogging operation being carried out by public health dengue prevention staff outside Bangkok, June 2012 / Credit: Sanofi Pasteur / Patrick de Noirmont