El Niño boosts infectious disease risk in the US

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With more El Niño events will come more ticks – and the diseases they spread.
M Phillips David / Getty Images

After horror reports of a flesh-eating bacterium which killed a man in just four days, and is spreading as oceans warm, an unnerving new study suggests climate change could also trigger an increase infectious bug-borne diseases in parts of the US.

A trio of researchers led by David Fisman at the University of Toronto in Canada analysed incident reports from the National Hospital Discharge Survey, which spans hospitals across the US between 1970 and 2010, and compared them with El Niño-Southern Oscillation (ENSO) events, which can dump vast amounts of rain on the western US (among other effects).

They found bug-borne diseases increased in the 12 months following an ENSO event – particularly tick-borne disease – in western regions of the US.

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And with massive ENSO events tipped to arise more frequently as the climate changes, this could have huge implications for healthcare.

The work was published in the Proceedings of the National Academy of Science.

ENSO is a complex weather phenomenon characterised by changes in sea surface temperature and atmospheric pressure over the Pacific Ocean. An El Niño year dumps rain onto the west coast of the US – perfect conditions for ticks to breed.

Non-Western regions don’t get let off lightly. After an ENSO event, the northeast in particular sees an increase in enteric disease risk.

Because ENSO occurs over the United States at irregular intervals, the researchers say it could provide a handy framework to study wider implications.

“The periodic nature of ENSO may make it a useful natural experiment for evaluation of the impact of climatic shifts on infectious disease risk,” they write.

The researchers say experts have been talking about the link between disease and environmental change since Hippocrates’, and yet very few studies have examined the relationship in the US today. 

And we shouldn’t assume that western medicine will be able to handle the changes that could arise. 

“As climate and weather continue to shift ever more rapidly, infectious disease control practitioners in high, middle, and low income countries all need to develop improved understanding of the impact such shifts may have on infectious disease,” says the paper.

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