“The perception of safety has already been attacked,” said Dr. Duffy. “You can see how vulnerable tourism-dependent countries are to a crisis like this, and I’m calling it a crisis because they’re starting to roll out the media campaign and the crisis response.”

Dominican leaders have also grown more defensive, asserting repeatedly that the country is safe while sometimes hinting at possible conspiracies aimed at the Dominican Republic’s lucrative hotel industry, including attempts to undermine the president’s ruling party. Mr. García, the tourism minister, declined to discount such theories.

“I don’t know who’s behind this campaign, but if there’s someone behind it, they’ll become known,” Mr. García said.

Some relatives of Americans who died in the country are relating harrowing tales of pleading with hotel employees for ambulances, long waits to retrieve the bodies of their loved ones and callous responses from Dominican officials.

Dawn McCoy, whose husband, David Harrison, died while on vacation in July 2018 at the Hard Rock Hotel, said that she wasn’t suspicious about his passing until she learned of the recent spate of deaths. The couple’s trip last year was their 19th visit to the Dominican Republic.

“I like to say, we were lucky 18 times,” she said.

Feeling ill with what he initially thought was food poisoning, Mr. Harrison had left his wife and son at the pool and returned to their room, where he slept for more than six hours, she said. The couple then went to the casino until about 2:30 a.m., and returned to the room after Mr. Harrison again felt ill.

“If we were at home, I would tell you to take me to the hospital,” Ms. McCoy recalled him saying.

Just after 5 a.m., Ms. McCoy woke up to find her husband soaked in sweat and grunting. Her son, just 12 at the time, pressed on Mr. Harrison’s chest, trying to perform CPR. “He was just doing what he had seen on TV,” Ms. McCoy said.