Two academic studies were performed to attempt to estimate the scope of mortality post-Hurricane Maria in Puerto Rico

The Harvard Mortality Study utilized a rapid and inexpensive survey-based approach that is frequently used in areas experiencing disasters with limited resources.  From the survey data, the study estimated a mortality rate of 14.3 deaths (95% confidence interval [CI], 9.8 to 18.9) per 1000 persons from September 20 through December 31, 2017. This rate yielded a total of 4,645 excess deaths during this period (95% CI, 793 to 8498), equal to a 62% increase in the mortality rate as compared with the same period in 2016. The mortality rate remained high through the end of December 2017, and one third of the deaths were attributed to delayed or interrupted health care.

The Puerto Rico local government commissioned the George Washington University to complete a second study to calculate excess mortality by analyses of past mortality patterns (mortality registration and population census data from 2010 to 2017). The intention of this study was to predict the expected mortality if Hurricane María had not occurred (predicted mortality) and compare it to the actual deaths that occurred (observed mortality). The difference estimates the excess mortality. This study although more expensive and theoretically more thorough, yielded similar results as the Harvard estimates. Total excess mortality post-hurricane using the migration displacement scenario was estimated to be 2,975 (95% CI: 2,658-3,290) for the total study period of September 2017 through February 2018. Regardless of these efforts, a formal recount of deaths due to Hurricane Maria was not requested by local government, and the number of deaths attributed to Hurricane Maria reported to National Center for Health Statistics is less than 60.