The surprise toll of tropical cyclones on our health
Research suggests that the health effects of tropical storms like Cyclone Chido could be felt for decades after they hit.
- 16 December 2024
- 4 min read
- by Linda Geddes
Close to a thousand people are feared dead after Cyclone Chido hit the island of Mayotte, off the east coast of Africa.
The tropical cyclone is the latest in a series of exceptionally severe storms and hurricanes to have made landfall during 2024. But while their consequences are often counted in the immediate numbers killed and injured, new research suggests they should instead be regarded as broader events with health consequences potentially stretching for decades.
Tropical cyclones are intense rotating storms that form over warm waters, triggering high winds, heavy rainfall and storm surges.
The immediate health impacts of cyclones – also known as hurricanes or typhoons in different parts of the world – are well known. They can cause physical trauma caused by flying debris and collapsed buildings or diarrhoeal and mosquito-borne diseases that result from damaged infrastructure and lingering pools of floodwater. However several recent studies have begun to investigate the longer-term impacts on people’s health.
Mounting evidence suggests that hurricane victims experience a greater incidence of cardiovascular disease in the following weeks and months, due to increased stress around the time of the storm and in its aftermath. These storms can also disrupt healthcare, which can make it difficult for people with new or pre-existing conditions to receive treatment.
Longer-term picture
In the latest such study, Rachel Young and Solomon Hsiang at Stanford University’s Global Policy Laboratory set out to estimate the wider impact of hurricanes on all causes of death, by investigating how death rates within a state changed in the 20 years after it was hit by a tropical cyclone.
Analysing the data for all 501 such storms occurring in the contiguous US (the 48 states that touch one another, plus the district of Columbia) between 1930 and 2015, they found that while the immediate death toll of each cyclone was 24 people on average, by expanding this to cover those who died earlier than would have been expected in the absence of the disaster, the death toll rose to between 7,170 and 11,430 individuals.
The research, published in Nature, also found that the rate of such indirect premature deaths was relatively higher among black populations and those who were infants at the time of each storm.
“During the period of study, we estimate that tropical cyclones contributed to more deaths in the contiguous US than all motor vehicle accidents, infectious diseases or US battle deaths in wars,” Young and Hsiang said.
While they acknowledged that the scale of the impact was “surprising”, they added that their findings were consistent with “a growing literature indicating that climatic conditions generally, and tropical cyclones specifically, have larger and more enduring effects than previously recognised.”
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Indirect deaths
Although the study didn’t identify the underlying mechanisms contributing to these deaths, Young and Hsiang suggested five potential explanations that could be explored:
- economic disruption which could affect household spending, such as on insurance;
- changes to social networks and support, such as because of people moving away from family or neighbours;
- altered government spending, which might reduce healthcare spending;
- changes in the natural environment exposing people to greater harm from disease vectors or harmful chemicals;
- and heightened physical or mental stressors affecting people’s longer-term health.
“Identifying the underlying origin of these health outcomes should prompt research and policy to mitigate this human toll,” they said.
Writing in The Guardian, Prof Devi Sridhar, chair of global public health at the University of Edinburgh, UK, noted that the study was notable as the first systematic attempt to look across hundreds of natural disaster events and attempt to capture their full impact in terms of deaths over decades.
“While the study focused on hurricanes and similar storms in the US, that type of methodology could be used to study the long-term health impacts of other disasters, from climate floods to heatwaves, and could even be broadened to understand the indirect health impacts of any kind of societal shock – whether a natural disaster or conflict,” she said.
