Almost 3,000 people died in Puerto Rico in the six months after Hurricane Maria as a result of the storm, with the elderly and improverished most affected, according to a long-awaited independent study ordered by the USA territory's government.
The new estimate of 2,975 dead in the six months after Maria devastated the island in September 2017 was made by researchers with the Milken Institute School of Public Health at George Washington University.
Carlos Santos-Burgoa, the professor of global health who was the lead investigator of the study said: "We lack a culture of preparedness".
The report, which analyzed processes related to death certification, says that physicians and forensic physicians are among those in Puerto Rico who are authorized to complete death certificates, but that most physicians have no formal training in how to do so.
The U.S. federal government has been heavily criticized for its response to the storm and the island's recovery efforts.
Puerto Rico needs to conduct after-action reviews and use those, along with the results of the study, to create a new crisis and emergency risk communication plan, one that is integrated with government agency and municipal plans, has community and stakeholder involvement, and is aligned with the possibility of catastrophic disasters.
For comparison, the death toll from 2005's Hurricane Katrina - the costliest hurricane in U.S. history - was far lower, and estimated at 1,833.
The finding is nearly twice the government's previous estimate, included in a recent report to Congress, that said there were 1,427 more deaths in the three months after the storm than the average for the same period over the previous four years.
The latest Puerto Rico figure was derived from comparisons between predicted mortality under normal circumstances and deaths documented after the storm, a number that turned out to be 22 percent higher.
In early October 2017, Trump expressed satisfaction with the federal response to Maria, saying it compared favourably with a "real catastrophe like Katrina".
Santos-Burgoa said the high death toll, ranking Maria among the worst natural disasters in United States history, was evidence that "we lack a culture of preparedness".
That figure was always risible - particularly when you consider that the 150 miles per hour (241 kmh) winds caused around $90bn worth of damage and left households for, on average, 84 days without electricity; 64 days without water and 41 days without cellular telephone coverage. Men 65 and older were also found to be at heightened risk. "Although the official death count from the Puerto Rico Department of Public Safety was initially 64, the toll appears to be much higher", wrote the report authors. "If enacted, the recommendations of this report could help save lives in Puerto Rico and beyond".