The United Nations has warned that El Nino poses a "significant" threat to global health as the world prepares for a climate cycle that is forecast to be among the strongest on record.
The natural weather phenomenon, associated with warming surface waters in the Pacific Ocean, can trigger higher temperatures as well as periods of severe drought and widespread flooding. Its effects are already being felt across regions stretching from Central America to Indonesia.
El Nino could increase risk of malaria, dengue and cholera
The World Health Organization (WHO) has warned that the changing weather conditions associated with El Nino could create favourable environments for infectious diseases.
Periods of heavy rainfall can provide conditions that support the spread of cholera as well as the breeding of disease-carrying mosquitoes. This could contribute to an increase in illnesses including malaria, chikungunya and dengue fever.
"The most severe impacts will be experienced while climate shocks intersect with weak health systems, limited access to healthcare, food insecurity, displacement and humanitarian crisis," warned Teresa Zakaria, WHO's Unit Head for Risk Reduction, Humanitarian Operations and Climate Change.
WHO calls El Nino a 'risk multiplier'
Zakaria described El Nino as "a significant public health threat" and a "risk multiplier", urging countries to take action before its potential effects develop into a wider health crisis.
"We have a window of opportunity to act now, before these risks become a crisis," the doctor told reporters in Geneva.
The WHO has highlighted the need for countries to prepare health systems and vulnerable communities for the potential combination of extreme weather, infectious diseases and disruptions to healthcare access.
El Nino forecast to be strongest in four decades
Earlier in September, the UN's World Meteorological Organization (WMO) warned that the current El Nino could be the strongest since comparable records began around four decades ago.
The organisation has also warned that the climate impacts associated with the phenomenon could continue well into 2027.
El Nino is a naturally occurring climate pattern and is not caused by climate change. However, scientists expect the phenomenon to intensify heat and weather extremes on a planet that is already warming because of human-caused greenhouse gas emissions.
Why this El Nino could be different
The combination of El Nino and already elevated global temperatures could make the current cycle particularly significant.
"Every El Nino is different," said Armel Castellan, an adviser on extreme heat at the WHO-WMO Climate and Health Joint Programme.
"However, this El Nino, coupled with temperatures that were already record-breaking, is what makes this one unique."
El Nino and global health risks
El Nino can influence weather patterns far beyond the Pacific, potentially bringing heat, drought and flooding to different parts of the world.
These conditions can have knock-on effects on public health. Flooding and heavy rainfall can increase exposure to waterborne diseases and create breeding grounds for mosquitoes, while extreme heat and drought can worsen food insecurity and place additional pressure on healthcare systems.
The UN and WHO are therefore urging countries to use the current window to strengthen preparedness and reduce the health risks associated with the anticipated El Nino cycle.
Inputs from agencies
