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Climate Change Can Make You Vulnerable To Diseases

Flash floodingThe earth is 4.5 billion years old. It has seen a lot of changes over the centuries from phases of extremely high temperature to the periods of permafrost, a lot about these climatic changes is known because of the remains found in the corals, rocks, ice, trees and fossils. These climatic changes have brought about wiping out of the most powerful species of those times. Human interventions, increased level of greenhouse gases has accelerated the rate of this change.

Carbon dioxide is one such gas that is responsible for trapping the heat and causing the climate to change. For ages the level of carbon dioxide in the atmosphere did not exceed 300 parts per million until recently, when the level of carbon dioxide recorded at Mauna Loa was found to be 397.64 parts per million (PPM) in September 2015.

The changing climatic patterns are enough to bring about catastrophe. Extreme events like frequent floods, droughts, increased forest fires and changed precipitation patterns, ocean acidification (due to increased absorption of carbon dioxide by the upper layers of ocean at the rate of 2 billion tons per year), accelerated health issues and introduction of new deadly diseases are now much more prevalent than what it was in the past.

The worst hit by climate change would be the poor developing nations of Asia, Africa, etc. who are not equipped to deal with this wrath of nature. India too will witness major environmental, ecological and economic setbacks. Extreme cold and heat conditions coupled with air pollution and aero allergens will also likely increase the vulnerability towards the infectious diseases.

Mosquito_Anopheles stephensiIPCC’s report (March 2014), provided evidence that climate change poses great danger to human health and also affects food, water and nutrition security. The Bulletin of WHO (World Health Organization) has also shown an inextricable linkage between climate change and human health. Increased levels of black carbon, carbon dioxide and other short lived pollutants due to increased air pollution contributes to almost 1 death in every 8 deaths. There are also evidences showing clear relation between infectious diseases and climate change.

Almost, one lakh fifty thousand deaths have been estimated in low income countries due to climate change by the WHO. Malaria, a vector borne disease which was earlier thought to be influenced by climatic variations like heavy monsoon rainfall and excessive humidity has been shown to have a 5-fold increased risk after an each El-nino event. According to WHO, climate change has the potential to increase mortality related to weather, cause heat strokes, skin and eye diseases, deaths due to storm and floods, increased incidences of vector borne diseases and diarrhoeal diseases, malnutrition, impaired growth in children due to alteration in food productivity and respiratory disorders due to air pollution. The WHO study showed that the temporal and spatial distribution of diseases like malaria and dengue have been projected to rise due to favourable temperature ranges causing prolonged peak periods for the vector borne diseases bringing about variations in the dynamics of these vector borne diseases. A study also quantitatively showed that cholera was strongly related to inter-annual climatic variations in the study area of Bangladesh.

IPCC has also projected an increased heat related mortality and malaria cases in India due to climate change. Major vector borne diseases in India as reported in 2010 can be tabulated as below.

Diseases Cases/annum Deaths
Malaria 1.59 million 1023
Filariasis 600 million (total burden)
Kala-azar 28941 105
Dengue 28292 110
Chikungunya 59535 (23.26% confirmed) (as reported in 2007)
Japanese Encephalitis 5149 677


The chikunguniya outbreak of 2005 that affected almost 1.4 million people in India and 255,000 people in Réunion (French island in Indian Ocean), was an alarm for the world that these episodic outbreak of dengue, malaria, chikunguniya in Africa, Southeast Asia, etc was closely related to the rising temperatures of the Earth. Vector diseases, diarrhoeal diseases and their transmission are affected by humidity, precipitation and temperature.

Climatic conditions due to changing weather patterns would hence become more favourable for the spread of these diseases like for example the transmission window for malaria is likely to get widened up in case of India and it is expected that by 2050 the disease would reach northern states of the country for the very first time.  These diseases, causing mortality and morbidity was a result of warmer temperatures and changing rainfall patterns which allowed and supported the thriving of these vectors in the areas, they were never expected to be found therefore increasing the incidences of these vector borne diseases.

The world would also witness increased deaths due to food insecurity, like in France and Italy where a 30% decrease in maize yield was seen in 2003 due to the heat wave. A study also estimated that climate change may inflict a reduction between 4 to 26% in the net farm income for the Indian farmers. The diverse impacts of environmental changes inflicting various infectious diseases can be tabulated as below.

Environmental changes Example diseases Pathway of effect
Dams, canals, irrigation Schistosomiasis Increased Snail host habitat, human contact
Malaria Increased Breeding sites for mosquitoes
Helminthiasies Increased Larval contact due to moist soil
River blindness Decreased Blackfly breeding, decreased disease
Agricultural intensification Malaria Crop insecticides and vector resistance

haemorraghic fever

Increased rodent abundance, contact
Urbanization, urban crowding Cholera Decreased sanitation, hygiene; increased water contamination
Dengue Water-collecting trash, increased Aedes aegypti mosquito breeding sites
Cutaneous leishmaniasis Increased proximity, sandfly vectors
Deforestation and new habitation Malaria Increased Breeding sites and vectors, immigration of susceptible people
Oropouche Increased contact, breeding of vectors
Visceral leishmaniasis Increased contact with sandfly vectors
Reforestation Lyme disease Increased tick hosts, outdoor exposure
Ocean warming Red tide Increased Toxic algal blooms
Elevated precipitation Rift valley fever Increased Pools for mosquito breeding
Hantavirus pulmonary syndrome Increased Rodent food, habitat, abundance


South East Asia Region accounts for 30% of the world’s total poor and is home to about 26% of the total world’s population. This region already under the disproportionate burden of the communicable diseases, is highly vulnerable to climate change due to its high population and may witness disastrous impacts. The 4th Assessment Report of IPCC of 2007 correctly highlighted that the vulnerability because of climate change also depends on the developmental pathway taken. A sustainable pathway can greatly reduce the vulnerability and many impacts can be delayed, reduced and also avoided. Limited scientific knowledge and expertise, improper legislation for public health, lack of proper infrastructure, financial and human resources are a barrier to effective combating of these serious issues and detrimental health impacts of climate change.

The adverse impacts of the changing climate would be unavoidable even with the best mitigation measures alone therefore it is important to have proper adaptive measures too. According to eleventh planning commission report of India, the best adaptive measure is growth and development itself as it increases technological and economic capability and reduces the vulnerability of a nation.

The climate change council of the Prime Minister of India also intends to compile a National Action Plan as India’s National Report on Climate Change consisting of all the actions proposed and taken to address the impinging problem of climate change on forests, agriculture, water resources, coastal areas and health.

It is important to pursue a sustainable pathway, increase adaptive capacity and develop the regional capacity for effectively protecting the human health and environment in the face of climate change.

Note: The value 397.64 ppm shows recent monthly average carbon dioxide measured at Mauna Loa Observatory, Hawaii.


Image credit: Flood, Mosquito

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