Why tropical cyclone survivors keep dying weeks after the storm ends

Tropical cyclones, known as hurricanes or typhoons depending on the region, are among the world’s most destructive weather systems. Each year, they affect about 20 million people and cause around 51.5 billion US dollars in damage. Yet the real danger often begins after the winds fade and floodwaters remain.

Researchers from Monash University and their partners examined 14.8 million death records across 1 356 communities in nine countries between 2000 and 2019. They identified 217 cyclones during this period and measured how deaths rose in the weeks following each event. The results showed that mortality peaked within the first two weeks and then declined rapidly, a consistent pattern across regions.

The greatest post-cyclone mortality came from kidney disease, with deaths nearly doubling in that two-week window. Injuries were the second most common cause, followed by diabetes, infectious diseases, and respiratory conditions. These delayed deaths often result from power outages, blocked transport routes, and contaminated water supplies rather than direct physical trauma.

The study’s authors call this the “hidden health burden” of cyclones and warn that disaster responses remain too focused on immediate fatalities. When emergency crews depart, many hospitals and clinics remain without electricity, clean water, or medication delivery systems, setting the stage for preventable loss of life long after the storm has passed.

What the numbers reveal about death after the storm

The study used a two-stage time series model to analyze cause-specific mortality trends. In the first stage, each community’s weekly deaths were modeled with a quasi-Poisson regression and a distributed lag structure that accounted for delayed effects up to four weeks. In the second stage, results were combined across all communities using a multivariate random-effects meta-analysis to generate global estimates.

A cyclone day was defined as one where maximum sustained winds reached at least 63 km/h (39 mph). Researchers then linked death records with wind and rainfall data from the International Best Track Archive for Climate Stewardship to measure how mortality changed during and after cyclone exposure.

During the first two weeks after a cyclone, deaths from kidney disease increased by 92%, from injuries by 21%, and from diabetes by 15% for each additional day of cyclone exposure. More modest increases appeared for infectious, digestive, and respiratory diseases, and even for cancers. These figures translate into thousands of excess deaths globally every year.

Mortality was highest in regions with greater poverty and in areas rarely exposed to cyclones, such as Canada, Australia, and New Zealand. By contrast, communities in Taiwan and the Philippines, which experience cyclones frequently, showed smaller increases in post-cyclone deaths. Experience and preparedness appear to be key factors in saving lives once the winds stop.

When rain is deadlier than wind

One of the study’s most striking discoveries was that rainfall, not wind, was more strongly associated with post-cyclone deaths from cardiovascular, respiratory, and infectious diseases. Flooding and contaminated water sources create persistent health threats that last long after the storm has ended.

The researchers found that rainfall intensity had a more consistent relationship with mortality than wind speed. Wind-related risks rose sharply only when maximum sustained winds exceeded about 126 km/h (78 mph). Beyond this threshold, deaths from injuries, neuropsychiatric disorders, and diabetes increased steeply.

This means that slower-moving, rain-heavy cyclones may pose greater long-term health risks than faster, windier ones. Flooding can disrupt medical supply chains, spread pathogens, and prevent emergency care access for extended periods. These indirect consequences often outlast and outweigh the immediate danger of high winds.

The authors recommend that early-warning systems highlight rainfall hazards alongside wind forecasts. Public health agencies should prepare for surges in waterborne diseases, dialysis disruptions, and medication shortages following heavy rain events, as these are the conditions most closely linked to delayed mortality.

Inequality and the human cost of vulnerability

The study exposed deep inequalities in how communities experience the aftermath of cyclones. People living in high-deprivation areas, those with limited healthcare access, poor infrastructure, and low income, faced significantly higher risks of death across almost every disease category. The most pronounced differences occurred in kidney, digestive, and infectious diseases.

Socioeconomic deprivation amplifies vulnerability in multiple ways. Poorer communities are more likely to be located in flood-prone zones, less likely to own vehicles for evacuation, and often lack backup power for medical equipment. When health services collapse, these disadvantages translate directly into higher mortality.

Age and gender also shape risk. Older adults aged 60 and over had higher death rates from kidney disease, likely because dialysis or blood pressure treatments were interrupted. Younger adults under 60 showed greater mortality from respiratory and neuropsychiatric causes, possibly linked to cleanup exposure or psychological stress. Women were more likely to die from respiratory illnesses and injuries, while men had higher mortality from kidney disease, diabetes, and mental disorders.

These differences show the need for tailored disaster preparedness. Effective cyclone response must include gender- and age-specific health plans, ensuring continued access to chronic disease care, mental health services, and emergency medical support for vulnerable populations.

Understanding how the science was done

The research builds on earlier studies that linked cyclones to deaths in single countries such as the United States and China. Previous work found modest increases in mortality, but those studies were limited to one storm or narrow disease categories. The Monash-led analysis advances the field by applying consistent statistical methods across multiple countries and using both wind and rainfall data.

The model used in this study—quasi-Poisson regression with a distributed lag non-linear structure—captured short-term spikes in deaths while controlling for temperature and seasonality. This allowed the researchers to distinguish cyclone-related effects from normal seasonal mortality fluctuations.

To test for bias, the team ran extensive sensitivity analyses and applied a double negative-control model, which checks for unmeasured confounders. The results remained consistent across all tests, supporting a direct causal link between cyclones and increased deaths from several diseases.

While comprehensive, the authors acknowledged some limitations. Exposure was measured at the community level, so individual variations in cyclone experience were not captured. Several low-income, cyclone-prone nations such as Bangladesh and Vietnam lacked sufficient mortality data for inclusion, suggesting that the true global impact may be even greater.

How to save lives after the next cyclone

The findings call for an urgent shift in how governments prepare for and respond to cyclones. Health departments need to plan for secondary waves of illness that occur after the storm. Hospitals should maintain emergency power for dialysis, refrigeration for insulin, and secured supply chains for essential drugs.

Meteorological agencies should work with health authorities to integrate rainfall forecasts and disease risk models. Doing so would allow targeted warnings for vulnerable populations, enabling pre-emptive evacuations or medical interventions before storms arrive.

Governments must also prioritize investments in deprived communities, where the death toll is highest. Reducing inequality is not just a social priority but a public health necessity during climate-related disasters. Wealthier regions can offer lessons in preparedness that must now be extended to newly vulnerable areas.

References:

¹ Cause specific mortality risks associated with tropical cyclones in multiple countries and territories: two stage, time series study – Wenzhong Huang et al. – The BMJ – November 5, 2025 – https://doi.org/10.1136/bmj-2025-084906 – OPEN ACCESS

² We studied 217 tropical cyclones globally to see how people died. Our findings might surprise you – The Conversation – November 6, 2025

Reet Kaur

I’m a science journalist and researcher at The Watchers, contributing to the Epicenter edition, where I cover peer-reviewed scientific research and emerging discoveries across Earth and space sciences. With a background in astronomy and a passion for environmental science, I’ve worked in shark and coral conservation in Fiji, conducting reef and shark-behavior research, contributing to mangrove restoration, and earning PADI Open Water and Coral Reef Certifications. I bring a blend of scientific rigor and storytelling to illuminate the discoveries shaping our planet and beyond.

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