Editor’s note: This article is part of a joint editorial initiative between the National Association of Community Health Centers and Direct Relief.

Most of the deaths from hurricanes aren’t caused by drowning or flying debris. They’re caused by the disruptions hurricanes inflict upon people’s lives, displacing people from their homes and communities, disrupting their access to healthcare, wreaking havoc on their finances, and putting them under severe stress. This sets them on a path to poor health that eventually cuts short their lives.

A newly published study in Nature finds that long-term excess deaths attributable to tropical cyclones (called hurricanes in North America) can be 300 or more times higher than immediate deaths. The authors tracked the effects of all 501 hurricanes that hit the continental United States between 1930 and 2015, and found that while the average tropical cyclone caused 24 immediate deaths, the storms on average led to between roughly 7,170 and 11,430 additional deaths in the 20 years after landfall.

The hurricane-prone climate in the U.S. “imposes an undocumented mortality burden that explains a substantial fraction of the higher mortality rates along the Atlantic coast and is equal to roughly 3.2–5.1% of all deaths,” said the study, by Rachel Young and Solomon Hsiang of the University of California Berkeley.

While the magnitude of the long-term mortality increase may be shocking, the underlying idea isn’t surprising to people familiar with the impact of Hurricane Maria, which devastated Puerto Rico in 2017. The storm’s official death toll was 64, but a widely noted 2018 paper in the New England Journal of Medicine found that Maria caused more than 70 times the number of excess deaths in the U.S. territory from September 20 through December 31, 2017 – a total of 4,645 additional deaths and a 62% increase in the mortality rate in the same period in 2016.

“Disasters trigger complex cascades of events that ultimately may cause additional future mortality,” the authors of the Nature paper wrote.

They cite a range of impacts of tropical cyclones that “might affect human health through complex chains of events,” including:

• Damage to infrastructure, homes, and businesses
• Population relocation
• Social and economic disruptions
• Ecological changes
• Reduced access to basic services
• Increased pollution
• Crop damage
• Insurance payouts
• Political actions

“For example, individuals may use retirement savings to repair damage, reducing future healthcare spending to compensate; family members might move away, removing critical support when something unexpected occurs years later; or public budgets may change to meet the immediate post-[cyclone] needs of a community, reducing investments that would otherwise support long-run health,” the study said.

The long-term health effects of hurricanes have important implications for organizations – including Direct Relief and the community health centers and free clinics it supports – focused on healthcare for populations that are already vulnerable before a storm hits. Rather than focusing primarily on treating illnesses, health centers emphasize keeping their patients healthy through managing chronic conditions that increase mortality, such as diabetes and hypertension. They also focus on outreach to populations left out of other private or public healthcare systems, including uninsured people and those living in healthcare deserts.

“The importance of this study is to shine a bright and very specifically empirical light on the true scale and scope of the long tail of hurricane impacts,” said Andrew Schroeder, VP of Research and Analysis at Direct Relief. “In that context, policymakers and NGOs should focus more than ever on reducing social vulnerabilities and increasing resilience before crises hit, while maintaining thoughtful, long-term, and consistent support for community health needs.”

“Health centers see this play out each and every day,” said Gianna Van Winkle, Director of Emergency Management at the Florida Association of Community Health Centers. She noted the efforts many health centers make to reach people who are isolated or don’t have other healthcare options. “This has been ingrained in health center culture here in Florida.”

The Nature study found that 59% of excess deaths “result from ‘other’ causes, a nonspecific category that includes diabetes, suicide, sudden infant death syndrome and other causes that are not individually recorded,” with cardiovascular disease the second-leading cause.

The impacts have an especially strong mortality impact “among infants (less than 1 year of age), people 1–44 years of age, and the Black population,” the study said. However, 99% of these infant deaths occur more than 21 months after the hurricane, indicating that the infants were not conceived prior to landfall. “This suggests that cascades of indirect effects following TCs, rather than personal direct exposure to the physical event, generate this mortality.”

Due to their exposure, southeastern states have the highest proportion of total deaths attributable to tropical cyclones. The data show that 13% of deaths in Florida, 11% of deaths in North Carolina, 9% of deaths in South Carolina, and 8% of deaths in Louisiana during this period can be traced to their hurricane-prone climates.