Incredible study reveals El Niño recently caused global disease outbreaks

1 Mar 2019

Image: © weyo/

Between 2015 and 2016, the weather phenomenon known as El Niño inadvertently set off a chain of events that led to global disease outbreaks.

The onset of climate change and its effects on the wellbeing of the human race are increasingly obvious, from prolonged droughts to chaos brought on by flooding. Now, extraordinary new research revealed by NASA researchers has found that one of the world’s most famous climate events directly affected the health of people across the globe.

The findings, published to Scientific Reports, revealed that between 2015 and 2016, El Niño brought weather conditions that triggered regional disease outbreaks across the globe. El Niño is an irregularly recurring climate pattern characterised by warmer-than-usual ocean temperatures in the equatorial Pacific, creating a ripple effect of anticipated weather changes in far-spread regions of Earth.

But during the 2015-2016 event, NASA’s researchers found that El Niño changed precipitation, land surface temperatures and vegetation, facilitating conditions for the transmission of diseases. The aftermath resulted in a surge of reported cases for plague and hantavirus in the US states of Colorado and New Mexico; cholera in Tanzania; and dengue fever in Brazil and south-east Asia, among others.

Stretched map of the globe showing increased ocean temperatures caused by El Nino.

Increased sea surface temperatures in the equatorial Pacific Ocean characterises an El Niño, which is followed by weather changes throughout the world. Image: NASA Goddard’s Scientific Visualisation Studio

These findings are the first to comprehensively show the public health impacts of a major climate event on a global scale.

“The strength of this El Niño was among the top three of the last 50 years, and so the impact on weather and therefore diseases in these regions was especially pronounced,” said lead author Assaf Anyamba. “By analysing satellite data and modelling to track those climate anomalies, along with public health records, we were able to quantify that relationship.”

The study used a number of climate datasets based on information and maps drawn up by NASA’s Terra satellite as well as the US National Oceanic and Atmospheric Administration.

‘It has the power to save lives’

Looking at a particular example, data showed that the numbers of reported cases for cholera in 2015 and 2016 in the east African nation of Tanzania were the second and third highest, respectively, over an 18-year period from 2000 to 2017. Increased rainfall brought on as a direct result of El Niño allowed for sewage to contaminate local water sources, such as untreated drinking water.

“Cholera doesn’t flush out of the system quickly,” Anyamba said, “so even though it was amplified in 2015-2016, it actually continued into 2017 and 2018. We’re talking about a long-tailed, lasting peak.”

The researchers believe this discovery is important for our understanding of seasonal forecasts, which could be crucial in the face of developing climate change.

“A lot of diseases, particularly mosquito-borne epidemics, have a lag time of two to three months following these weather changes,” Anyamba said. “So, seasonal forecasting is actually very good, and the fact that they are updated every month means we can track conditions in different locations and prepare accordingly. It has the power to save lives.”

Colm Gorey was a senior journalist with Silicon Republic