In Puerto Rico, the official government estimate for the number of people who died as a result of Hurricane Maria (the hurricane that struck the island in late September 2017) is just 64. But a new study from Harvard University, published in The New England Journal of Medicine, estimates that the true number is closer to 4,645—that is, more than 70 times the official estimate.

After Hurricane Maria struck Puerto Rico, the island went for months without proper water, electrical , or cellular service . Alsom the island was briefly embroiled in a scandal in which a $300 million government contract to rebuild the electrical grid was offered to a company called Whitefish Energy under unusual circumstances.

Puerto Ricans have sharply criticized the government headed by Governor Ricardo A. Rosselló. They claim it has been slow to restore street access from downed trees, as well as other basic utilities. The low "official" fatality count has contributed to the problem. Accurate measures of disaster-related deaths allow regions to properly prepare for future disasters and provide closure for families.

The researchers who conducted this new study visited a random sample of 3,299 houses in Puerto Rico and asked the responders to provide information about household members who had moved or died, as well as any infrastructure loss. From the answers, the researchers estimated that, throughout the island, 14.3 deaths had occurred per 1,000 people between September 20 and December 31, 2017. Using that number, Harvard estimated that 4,645 excess deaths occurred in Puerto Rico compared to the same period of time the year before.

The researchers even believe this number is an underestimate due to survivor bias. That is, only households with surviving members can respond, so households of people who died while living alone might be under-counted.

Exercise in counting

According to the Centers for Disease Control (CDC), deaths that occur due to unsafe conditions or loss of medical services caused by a hurricane or other weather events are attributed to that weather event.

The Harvard report suggests the difference between the government's estimate and the unofficial estimate may partly stem from a complicated process for counting natural disaster-related deaths in Puerto Rico. There, disaster-related deaths require a sign-off from the Institute of Forensic Sciences, which is based in the capital city of San Juan. "This requires that bodies be brought to San Juan or that a medical examiner travel to the local municipality to verify the death, often delaying the issuance of death certificates," the Harvard study wrote. In addition, it's generally hard to classify deaths that stem from a chronic condition but might have possibly been exacerbated by the conditions caused by the hurricane.

The New York Times, CNN, and Puerto Rico's Center for Investigative Journalism have all independently reported death tolls significantly higher than the 64 deaths the Puerto Rican government has been reporting.

The government of Puerto Rico stopped sharing data on mortality in December 2017. Around that time, according to NYT, the government commissioned a study from the Milken Institute School of Public Health at George Washington University to get a more accurate view of the mortality rate. That study is still being conducted, and results are not expected until later this summer.

The Harvard study was conducted without the assistance of the government, using psychology students and professors to conduct the surveys. Speaking to the Times, one of the surveyors said that the government needed to do door-to-door surveys to get a truly accurate picture of the death toll of Hurricane Maria. "Even if they were really doing a good job, it was really hard unless you did something like we did—go talk to people on the ground," said Juan Domingo J. Marqués, an associate professor of psychology at Albizu University San Juan Domingo.

People "died alone in their houses," Marqués added. "Nobody went there. Some of them were covered by a landslide, and months after they've not recovered the bodies."

Causes of death

According to the Harvard report, "interruption of medical care" was the leading reason for increased mortality after Hurricane Maria. The causes of those interruptions were more varied. 14.4 percent of households reported that they lacked access to medications, and 9.5 percent reported that they lacked access to electricity for respiratory equipment. 8.6 percent of households reported that medical facilities near them were closed.

When the researchers isolated responses from remote areas, 8.8 percent of households said they could not access 911 by telephone when they needed it.

"Growing numbers of persons have chronic diseases and use sophisticated pharmaceutical and mechanical support that is dependent on electricity," the report noted. "Chronically ill patients are particularly vulnerable to disruptions in basic utilities, which highlights the need for these patients, their communities, and their providers to have contingency plans during and after disasters."

The report also noted that households experienced an average of "84 days without electricity, 68 days without water, and 41 days without cellular telephone coverage after the hurricane and until December 31, 2017." When the survey was conducted in early 2018, many respondents said they still lacked access to electricity and cellular service.

The survey didn't just focus on the death toll of Hurricane Maria. It was also concerned with the number of people the Hurricane displaced. The median age of people who left a household and did not return (or were reported missing) was 25 years. Fifty-two percent of those people who moved did so within Puerto Rico. Forty-one percent went to the continental United States. However, the report notes that increases in death rates seemed to occur across age groups, despite displacement trends.

New England Journal of Medicine, 2018. DOI: 10.1056/NEJMsa1803972 (About DOIs).