Climate change as a public health emergency

When we talk about climate change, the conversation almost always veers toward rising sea levels or extreme weather events. Some may even talk about the economic disruption that these natural disasters can and do cause. However, few, if any, touch upon another dimension of climate change: the broad-spectrum medical crisis that changing planetary patterns can trigger, as climate change intensifies every disease we already know and opens the door to those we have yet to face.

Nowhere is this more visible than in India. Increasingly frequent and severe waterlogging due to excess rain in cities such as Mumbai is creating ideal conditions for waterborne infections including cholera, typhoid, hepatitis A and leptospirosis. Recurrent waterlogging overwhelms sanitation infrastructure, contaminates clean water supplies, and leaves urban populations exposed to serious illnesses.

Conversely, drought-prone regions are facing worsening water scarcity, forcing communities to rely on unsafe water sources, thereby increasing the burden of diarrhoeal diseases as well as chronic dehydration.

Expanding disease risk

Meanwhile, shifting seasonal patterns are driving a rise in infections, allergies and vector-borne diseases, as changing temperatures and rainfall cycles disrupt established trends and prolong pollen seasons. Disease windows are expanding, and their geographic reach is steadily widening, quietly accelerating climate-driven spread. Communities with no prior exposure lack immunity, while health-care systems in these regions remain underprepared to respond at scale. One major example of this is the exponential growth of mosquito-borne diseases, as rising temperatures have made previously inhospitable regions suitable for this insect. The impact on dengue patterns is already measurable in Delhi-NCR. The number of cases traditionally peaked in September but now peaks in November, as warmer and rainier conditions sustain mosquito populations for longer periods.

Malaria, once largely confined to endemic pockets of the Gangetic Plains and the warm, humid regions of central India, is now being reported in cooler areas such as Himachal Pradesh, where it historically had minimal presence.

Climate change threats

Climate change also triggers rising air pollution. As summers become increasingly hotter, greater reliance on air conditioning drives higher energy use and greenhouse gas emissions. These emissions contain elevated levels of PM2.5 — microscopic pollutants that penetrate deep into the lungs and bloodstream — exerting widespread effects across multiple organs in the body, particularly the lungs, heart and kidneys.

Fine particulate matter penetrates deep into the lungs, causing inflammation, reduced lung function, and exacerbating respiratory conditions such as asthma and chronic obstructive pulmonary disease.

These particulates can also damage blood vessels, accelerate atherosclerosis, and increase the risk of hypertension, heart attack and stroke. The kidneys are equally vulnerable, and chronic exposure can impair kidney function, reduce filtration efficiency, and contribute to the progression of chronic kidney disease.

Greenhouse gases also trap more heat in the atmosphere, creating a feedback loop that amplifies the very crisis we are trying to manage through air conditioners and other cooling appliances. This heat stress forces the heart to work harder to regulate the body’s temperature, increasing strain on the cardiovascular system. This can trigger complications such as hypertension, heart attack, and stroke. These conditions disproportionately affect people without adequate shelter, such as manual labourers who spend long hours working outdoors in extreme conditions.

Parts of the country, such as Odisha, Telangana, and Vidarbha, are reporting a rising number of heat-stroke-related deaths. In addition, rising night-time temperatures in urban pockets such as Delhi-NCR and Mumbai are eliminating the critical recovery window that the human body relies on to cool down after prolonged daytime heat exposure.

Infant health outcomes are also increasingly at risk — exposure to extreme heat and air pollution has been linked to preterm births and low birth weight among newborns.

Impact on food security

The health consequences of climate change also extend into food systems and nutrition. Extreme weather events and unseasonal rain disrupt crop cycles and reduce agricultural productivity, contributing to food shortages. The declining nutritional quality of food crops, combined with rising prices, further compounds the crisis, creating a hidden burden of micronutrient deficiencies and chronic malnutrition, especially among children.

Rising temperatures can also cause a decline in milk production, as cattle affected by heat stress compromise infant and child nutrition. These cascading effects on food security translate directly into weakened immunity and greater vulnerability to disease particularly among children and the elderly.

The warnings have existed for decades, but were largely overlooked. Climate change is no longer a distant threat — for public health in India, it is already a present reality. It is a multifaceted challenge. Treating it as purely environmental overlooks its profound human cost. Recognising it as a medical emergency is the first step toward responding with urgency.

Dr. Naresh Trehan is Chairman and Managing Director, Medanta

Published – April 07, 2026 12:08 am IST