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May 30, 2018

The official Hurricane Maria death toll is 64. The real figure may be closer to 5,000, study suggests.

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    About 4,600 people died in Puerto Rico in 2017 from causes related to Hurricane Maria, according to a new study published in the New England Journal of Medicine that calls Puerto Rico's official death toll of 64 "a substantial underestimate."

    When a disaster occurs, the whole hospital is our patient

    Hurricane Maria, a powerful Category 4 storm, tore through Puerto Rico on Sept. 20, 2017, with 140 mph winds. The storm knocked out power across Puerto Rico and affected the water supply for nearly half of residents.

    The federal government and Puerto Rico officials have faced criticism over the slow response time that left many residents without electricity, water, or access to medical care, the Washington Post reports. In addition, several independent researchers and news outlets have challenged the Puerto Rico Department of Health's (DOH) official death count related to the hurricane and response efforts.

    Study details

    For the latest study, a research team led by scientists at the Harvard T.H. Chan School of Public Health conducted in person surveys of a random sample of 3,299 households in Puerto Rico. The surveys, which were conducted over a three-week period in January, revealed a total of 38 deaths between the Hurricane and Dec. 31, 2017. The researchers converted that total into a mortality rate, extrapolated the number to the U.S. territory's total population of 3.4 million people, and finally compared that figure with official statistics from the same period in 2016 to determine excess deaths.

    According to NPR's "Shots," household surveys are a "widely accepted" method of estimating casualties in the wake of a disaster. However, those numbers can be misleading if the survey sample is not truly random or if some households were no longer standing after the disaster. The Harvard team suspects their findings may be an underestimate due to the latter potential for bias.


    Overall, the researchers concluded that the mortality rate in Puerto Rico had jumped 62% in the three months following Hurricane Maria. They estimated there were a total of 4,645 "excess deaths," or deaths that would not have occurred if the storm had not hit, between Sept. 20 and Dec. 31, 2017. However, because of the relatively small survey sample, the researchers estimated that the true number of excess deaths could range from about 800 to more than 8,000.

    Even the low end of that range is far higher than Puerto Rico's DOH's official estimate of 64 deaths. While the researchers noted that their figure was likely higher because it looked at a longer time frame than previous estimates, they also called DOH's figure "a substantial underestimate." The researchers also noted that it's likely the figure would continue to rise in 2018. Rafael Irizarry, a biostatistician on the research team, said, "We saw consistent, high rates, in September, October, November, December," adding, "There's no reason to think that on Jan. 1 this trend stops."

    The survey also showed nearly 10% of reported deaths were directly related to the hurricane, and one-third were related to "delayed or prevented access to medical care" following the storm. The researchers wrote, "In our survey, interruption of medical care was the primary cause of sustained high mortality rates in the months following the hurricane." In the months following the hurricane, the survey found:

    • 31% of households surveyed reported "disruptions to medical services";
    • About 14% of households had difficulty getting medications;         
    • 10% were without electricity needed to power respiratory equipment;
    • 9% faced access to care issues because of closed medical facilities;
    • 6% had doctors who were absent after the storm.

    Surveyed households reported waiting an average of 68 days after the storm to have water service restored and 84 days for electricity.

    Controversy over death count

    Caroline Buckee, a lead author of the news and epidemiologist at the Harvard T.H. Chan School of Public Health, said the study "provides a different kind of estimate and a different kind of insight into the impact of the hurricane." The researchers suggested that the government in Puerto Rico could use its methods in an even larger survey to reduce the large uncertainties in their findings.

    However, Roberto Rivera, a statistician at University of Puerto Rico at Mayaguez who has conducted his own research into hurricane-related death rates in Puerto Rico, said that the new study's figure sounds "really high." Rivera said the public will likely need to wait until DOH releases its updated death toll to see the true figure.

    Puerto Rico officials commissioned researchers from George Washington University's Milken Institute School of Public Health to estimate excess deaths, and those results are expected to be released this summer.

    Carlos Mercader, executive director of the Puerto Rico Federal Affairs Administration, said, "We have always expected the number to be higher than what was previously reported." Referring to the upcoming study from GW researchers, he said, "Both studies will help us better prepare for future natural disasters and prevent lives from being lost."

    The Harvard researchers wrote that understanding the hurricane's true effect on the death rate is important to help public health officials better prepare for future disasters and potentially ward off secondary deaths related to health care access issues (Harris, "Shots," NPR, 5/29; Kaplan/Khan, Los Angeles Times, 5/29; Fink, New York Times, 5/29; CBS News, 5/29; Hernández/McGinley, Washington Post, 5/29).

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