Disease, hunger and extreme heat: UN sounds alarm over El Niño

Geneva: A rapidly strengthening El Niño could trigger health consequences across the world, worsening malnutrition, cholera, mosquito-borne diseases and heat-related illness as extreme weather places additional pressure on vulnerable communities, United Nations agencies warned on Tuesday. 

The World Health Organization warned that the developing climate event poses a significant public health threat, with the gravest effects expected in places where droughts, floods and extreme heat collide with fragile health systems, limited access to care, food insecurity, displacement and humanitarian emergencies.

“The most severe impacts will be experienced” where those pressures overlap, Teresa Zakaria, head of the WHO unit for risk reduction, humanitarian operations and climate change, told reporters in Geneva.

Zakaria called El Niño “a significant public health threat, not just a climate phenomenon”, warning that its effects could extend well beyond changes in temperature and rainfall.

Among the most immediate concerns are malnutrition and cholera, which the WHO assesses as very high risks in areas affected by both drought and flooding.

Climate shocks can damage crops and livelihoods, reduce access to safe water and sanitation and place already stretched health services under further strain.

More than 150 million people are already experiencing acute food insecurity worldwide, according to Zakaria, with the number expected to rise as disrupted rainfall and extreme weather affect food production and household incomes. 

Changing temperatures and rainfall patterns could also create more favourable conditions for mosquito-borne diseases. The WHO has warned of increased risks from malaria, dengue, chikungunya, yellow fever and Zika, including the possibility that some diseases could spread into areas where they have not traditionally circulated.

Heavy rainfall and flooding can create breeding grounds for disease-carrying mosquitoes, while floods may contaminate water supplies and increase the risk of cholera. Drought, meanwhile, can deepen food shortages, worsen malnutrition and make access to clean water more difficult.

Extreme heat presents another concern, particularly for people with existing health conditions and those with limited access to cooling or medical care.

Armel Castellan, an extreme heat adviser with the joint WHO-WMO Climate and Health Programme, noted that the world had just experienced two record-hot months, while sea-surface temperatures were also at unprecedented levels.

As El Niño approaches its expected peak towards the end of 2026, much of the Southern Hemisphere, including southern Africa, South America and Australia, will be moving into its hottest season in early 2027. That combination could heighten the risks of drought, wildfires, smoke and deteriorating air quality, Castellan explained. 

The World Meteorological Organization earlier this month forecast that El Niño would intensify into a very strong event before peaking towards the end of the year. Its latest modelling shows a nearly 100 per cent likelihood that El Niño will persist through February 2027, with its effects on rainfall and temperature continuing well into next year. 

El Niño is a naturally occurring climate pattern associated with unusually warm ocean conditions in the tropical Pacific. It can reshape rainfall and temperature patterns around the world, increasing the likelihood of drought in some regions and heavy rain or flooding in others. The strength of an El Niño event, however, does not translate directly into the same level of impact everywhere. 

The current episode is unfolding against a backdrop of exceptionally high global temperatures, amplifying concern over its potential consequences.

“Every El Niño is different,” Castellan told reporters. But this episode is interacting with temperatures that were already breaking records, creating what he described as an unusual combination of climate risks.

The WHO is urging governments to use the months before the event reaches its peak to strengthen health-system preparedness, improve disease surveillance, protect continuity of medical care and ensure that medicines and other supplies are available in areas most exposed to climate shocks.

Zakaria urged governments, communities and humanitarian partners to act before those risks intensify.

“We have a window of opportunity to act now before these risks become crises,” she stressed.