Why climate change impacts human health so much
The impact of climate change on human health is a clear and present threat. Climate variables affect the quality of air we breathe, the water we drink, the food we eat and even dictate where we can live or work. Increased frequency of severe weather events – searing heatwaves, heavy downpours, floods and droughts – cause death and displacement, damage to public infrastructure as well as reduce the availability of food and drinking water. They also lead to infectious disease outbreaks on one hand and limit access to healthcare on the other. Recognising its need, the Government of India has added ‘human health’ as a mission in the National Action Plan for Climate Change in order to combat the impact on public health.
Ecological factors impact vector behaviour
Mosquitoes are highly sensitive to temperature, humidity and rainfall. Environmental and landscape changes coupled with rise in temperature and humidity levels influence vector behaviour and disease transmission. A case in point is the Indira Gandhi Canal project in the Thar Desert of Rajasthan, which has altered the ecological profile of the region. As a result, the malaria vector Anopheles culicifacies and Plasmodium falciparum have now overrun the wet and water-logged canal command areas.
An Indian Council of Medical Research (ICMR) study on tea gardens conducted across Assam, Meghalaya, Manipur and Sikkim found that as a result of deforestation, new irrigation channels, changes in crop pattern, use of pesticides and higher annual mean temperature, a new vector species, An. culicifacies has invaded the region and is gradually replacing An. minimus, a stream breeder, which thrived in the forested areas. This may have implications on vector control as An. Culicifacies is resistant to DDT, a commonly used insecticide. The low humidity and rise in temperature due to deforestation has limited the breeding of An. minimus and An. dirus, which favoured high humidity and low temperatures in forest areas.
Developing early warning systems and tracking outbreaks
Researchers at the Indian Institute of Public Health, Gandhinagar have created a heat vulnerability map of India, identifying places that are likely to suffer the worst from a spell of high temperature. The index can guide appropriate action plans to protect local communities and has helped reduce deaths due to heat stroke in Ahmedabad this year.
Leveraging space technologies and parameters like sea surface temperature and normalised difference vegetation index will help devise early warning systems for disease outbreaks. El Nino (a warm ocean current phenomenon that results in less rainfall) can cause extreme weather events and impact human health. Malaria epidemics have been associated with excess rainfall in arid areas or where rivers are transformed into pools, conducive for mosquito breeding.
A prediction model of the impact of climate change on malaria has been designed by the National Institute of Malaria Research (NIMR). An analysis of four vulnerable sectors, viz. the Himalayan region, north-east, Western Ghats and coastal region of India has shown that in a projected climate change scenario, Uttarakhand and Jammu & Kashmir are likely to witness opening up of new areas for malaria transmission and increase in period of transmission windows in north-eastern states.
A Centre of Excellence, funded by the Department of Science and Technology, has been set up at NIMR to study the impact of climate change on diseases such as Japanese encephalitis, chikungunya and dengue. An early warning system for Japanese encephalitis – JEWS – has been developed by ICMR’s Regional Medical Research Centre in Dibrugarh and the North Eastern Space Applications Centre, Shillong. JEWS employs technologies like Remote Sensing and Geographic Information System in conjunction with epidemiological risk factors to identify villages that may witness disease outbreak, 2-3 months in advance. Given its high precision rate, it is now being adopted in additional JE endemic areas of Assam.
Inclement weather conditions can have an immediate effect on morbidity and mortality. Managing these contingencies can put tremendous stress on the health system. To respond swiftly and effectively, health systems must be equipped to deal with emergencies arising from shifts in weather conditions. Forecast systems will give sufficient lead time to health authorities to strengthen their preparedness mechanisms and gear up well in time to deploy adequate control measures to deal with an impending disease outbreak. Solutions will come from technology and a better understanding of how people and organisations respond to crises. Research, of course, will need to show the way.
Soumya Swaminathan is secretary, Department of Health Research, Ministry of Health & Family Welfare and director general, Indian Council of Medical Research
The views expressed are personal