In 2017, Hurricane Maria delivered a terrible blow to Puerto Rico, leaving nearly the entire island without power. The government estimated that the storm killed only 64 people, but a Harvard study--published in The New England Journal of Medicine suggested that the actual death toll was 70 times higher.
Per USA Today:
Researchers at the Harvard T.H. Chan School of Public Health, however, surveyed more than 3,000 households on the battered island. By extrapolating those findings, researchers determined that at least 4,645 "excess deaths" occurred during the storm and the weeks that followed. The researchers said the number was conservative and that the death toll likely exceeded 5,000. Many of the deaths were due in part to power outages that crippled medical and other services.
This study made international headlines, for obvious reasons. The researchers' 95% confidence interval stretched between 800 and 8,000 (before adjusting for survivor bias, etc., which increases that count somewhat).
Since then, a draft of a report to Congress that requested $139 billion in recovery funds indicated that there were 1427 more deaths in the final four months of 2017 relative to the previous four years. This new figure has been pushed as the "real" hurricane death toll, though official statements have undermined this interpretation. Héctor Pesquera, the secretary of public safety put it bluntly: "This is not the official number of deaths attributable to Hurricane Maria."
What is the true number then? The Government of Puerto Rico commissioned a more rigorous study through George Washington University (GWU) Milken Institute School of Public Health to precisely document the hurricane's toll. So far, researchers have blown a deadline, but they hope to complete the project by summer's end.
What will the final number of dead be according to the GWU study?