The number of deaths attributed to Hurricane Irma, more than six months after its rampage across the Caribbean and the south-eastern United States, increased to 129 — more than twice the amount reported at the end of the storm.
It took years for Hurricane Katrina’s death toll to become fully known.
That number is still debated today, with figures used by disaster agencies varying by as much as 600 deaths.
And while the change in the number of dead from Hurricane Maria is perhaps the most dramatic — rising from 64 to a 2,975 after the Puerto Rican governor commissioned university researchers to review the count — it is common for death tolls in natural disasters to escalate weeks and months later because of deaths indirectly caused by a storm.
Deaths directly linked to a disaster include drownings from a storm surge or being crushed in a wind-toppled building.
On Friday, US President Donald Trump accused Democrats of inflating the death toll from Hurricane Maria to make him “look as bad as possible”.
He said 18 people had been reported dead when he visited the island on October 3, two weeks after the storm hit, though the US territory’s official death toll was raised to 34 later that day. After that, it climbed to 64.
Flooding can mean places are under water for weeks, hiding the dead. Some people may be swept miles away from their homes.
People may not be reported missing because friends and neighbours believe they evacuated and decided not to return.
The poor, disabled and elderly are at most risk after a storm hits because they often do not have the means to get out and are unable to get to food, water and medicines. Those are the deaths that commonly are added later.
Death tolls in some developing countries vary by the tens of thousands because typically it is not known how many people were actually ever living in affected areas.
Trump suggested that in Puerto Rico, many deaths had been added later “if a person died for any reason, like old age”.
There are discrepancies in how the deaths are recorded but disaster experts say that often causes an undercount.
Puerto Rico’s initial count of 64 included only people whose death certificates cited the storm. Outrage from thousands of families who said they had lost loved ones due to post-storm conditions pushed the territory to hire George Washington University to study how many more deaths than usual has occurred after the storm.
The university said it was an estimated 2,975 deaths, a figure that has been roughly corroborated by other, similar studies.
The direct death toll from Irma stands at 47 across the Caribbean and southern US, according to the National Hurricane Centre.
An additional 82 deaths — 77 of them in Florida — were indirectly caused by the storm.
The deaths included 14 people who died at a Florida nursing home that lost power and air conditioning.
It also took years to assess the death toll from Hurricane Katrina in 2005 despite the relative accessibility of the Gulf Coast.
About 1,800 died from Katrina, though some agencies still list it at 1,200.
