The post-2000 era is marked by rise of several new strains of vector-borne pathogens leading to unprecedented proliferation of infectious diseases worldwide. But among them all, dengue has emerged as the single most important arboviral disease. As WHO reports suggest, dengue is a year-round threat throughout the tropics.
About 390 million people, from over 125 countries, accounting for over half the global population, presently lie in the path of dengue. It includes the Americas as well, sharing 14 per cent of the global dengue burden, with majority occurring in Brazil and Mexico. But Asia tops the list worldwide. Over 70 per cent of the global dengue infection is concentrated in Asia, with India contributing to as much as 34 per cent.
In West Bengal, Kerala, Assam and Delhi, dengue is almost an annual routine. Specifically in West Bengal, where the death toll has been rising. Opposition parties are dumping slurs on the ruling party for engineering data and/or warning public hospitals against citing dengue as cause of death. Central agencies are accusing that the state hasn’t even provided accurate accounts yet or taken any initiative for ‘dengue mapping’ which is critical for strategic intervention. And on top of all, there is loud public outcry against shabby public healthcare systems and shortage of medicines. Currently, many pharmaceutical stores in Kolkata are out of Calpol 650, the most commonly prescribed drug for dengue. But city stores are making quite a fortune over mosquito nets.
How’s this all going to affect health and hygiene in coming years?
Unfortunately, global research predicts substantial rise in intensity and geographic spread of dengue in the coming years, citing climate change as a major driver. Global climate research has shown that average surface temperature has increased by 0.74°C in the 20th century, Arctic sea ice has been shrinking by 2.7 per cent per decade leading to annual rise of sea-level by about 1.8 mm since the early 1960s.
In warming climate, likelihood of emergence, resurgence and redistribution of dengue pathogens is greatly amplified. In fact, changes in ambient temperature alone can raise the biting rates, egg and immature mosquito development, extrinsic incubation period (development time of virus in the mosquito), and survival at all stages of the life cycle of the mosquito. The IPCC predicts an average temperature rise of 1.5–5.8°C during the 21st century, accompanied by increased occurrence of heat-waves.
Precipitation provides habitats for the aquatic stages of its life cycle and influences distribution. Increased precipitation under changing climate will potentiate more vegetation growth and allow for expansion in the host population. Mutual interplay of precipitation and evaporation regulates the size, population, and behavior of mosquitoes. Climate research also reveals that extreme weather events are becoming more frequent, which alters the natural flood-drought cycles in many parts of the world including India. Under such aberrant conditions, likelihood of dengue is greatly amplified. Increase in flooding events accentuate vectors’ breeding rate. On the other hand, drought alters river flow, creating stagnant pools and supports vector ecology.
In summary, global climate predictions clearly indicate that we are up for more recurrent and violent outbreaks of dengue (and other vector-borne diseases) in coming years. Responding to global disease burden under a changing climate is going to be a major challenge. But climate in our times is mostly governed by aggressive human expansion – urbanisation, to be specific. Dengue is more an urban phenomenon. Recent economic boom has made urban wealth indicators soar sky-high. With that, urban lifestyle has hurled itself into the path of extreme consumerism. The downside is that climate’s been pushed to the brink.
Agricultural expansion/intensification, enhanced irrigation, dam construction, unregulated waste disposal and open-air incineration, vehicular and industrial emission, unplanned construction, shabby peri-urban dwellings, streets littered with puddles and potholes, clogged/polluted waterways, lack of regular weeding/spraying…our precious urban space is constantly being ‘trashed’.
With elevated purchasing capacity, we have practically molded ourselves into a ‘throw-away’ society, piling heaps of waste and miles of degraded land, which could lead to climatic shifts and enhance life cycles of pathogens/vectors. This strains the urban healthcare system to the limit.
True that urban health is so compounded by this climate-human nexus that meeting with infrastructural demands is quite an uphill task for governments. Policies aimed at leashing down urbanisation are compounded by numerous mutually reinforcing factors. But something needs to be done. Each year pulling off some emergency measures in a jolt won’t help anymore. They have to come up with some long-ranging scientific and social adaptation strategies, contextualized to geographic and socio-economic traits, to preempt climatic shifts.
But for that, there is need of robust mathematical approximations on the likely shifts in meteorological parameters, at least for cities that have recurrent crises over dengue. There could be two ways to get to that: (1) predict what meteorological parameters will change that may cause elevated health hazards and (2) identify all parameters favoring pathogens, hosts/vectors, or transmission to be active.
However, there are several confounding factors therein: (1) interactions between meteorological parameters and socio-economic drivers are highly complex, occurring on multiple spatio-temporal levels, frequently leading to non-linear feedbacks; (2) as climate changes, so does the origin, intensity, and mode of disease transmission. Newer strains of pathogens emerge every season that make detection/prevention more difficult. It is like trying to solve a Rubik’s cube that is constantly fighting back.
One perceivable approach for the government is to commission universities and research organisations with such tasks. It is commonly practiced in the developed world – inviting scientific proposals from academic institutions to assess climate change and its likely impacts on environment, health and economy. Same goes for up-scaling of health support systems in view of emergence of newer strains of pathogens. Unfortunately, government’s academia connect is still in a pretty nascent state in India. This has to change. We can only strive for maximum benefit within a participatory framework.
But for anything there has to be a positive mindset on part of the state government. They have to come out of their stand of denial about the intensity of the disease and make all relevant information available to central authorities and to citizens. Let research flourish on public support systems no matter how embarrassing it may appear eventually. Efforts to map diseases have to begin immediately to (1) catalogue cases, (2) identify regions more prone to infection, and (3) how both may change over time.
The public’s share of the responsibility cannot be ignored either. We have to force ourselves into some draconian restrictions to leash evasive tendencies that impinge upon nature and usher such health crises each year. We must agree to compromise in everyday choices. Interventions aimed at climate change and/or disease containment cannot take effect overnight. It’s time we understood it. We must set ourselves on a course to preserve urban spaces to keep climate under check and make the environment a part of our daily existence.
Of course, the government can’t/shan’t turn away from their obligations. But can we either? It’s like that quote: there are no passengers on spaceship earth: we are all crew.
(The writer is on the environmental studies faculty and co-Director of the Center for Environment, Sustainability and Human Development (CESH) at the OP Jindal Global University Sonipat)