“This will have many repercussions,” said Harold Cárdenas, a popular Cuban blogger who recently started a master’s degree program in international relations at Columbia University. “The most immediate is it will perpetuate estrangement, not just political, but physical. There will be a price, and it will be paid by Cuban families.”
The travel notice, which “warns U.S. citizens not to travel to Cuba,” could deal a blow to the island’s tourism sector, one of its economic engines, and call into question the viability of dozens of projects under construction. Since diplomatic relations with Washington were restored, Havana has begun an ambitious program to build up its dilapidated tourism infrastructure. It announced plans to partner with international hotel chains and other investors to build hundreds of new projects by 2030, including resorts with golf courses and marinas.
Americans remain nominally barred by law from traveling to Cuba as tourists. Yet the number of American visitors increased sharply after the Obama administration relaxed travel restrictions and began allowing airlines to offer service to Cuba in 2016.
Through August, more than 475,000 American citizens traveled to Cuba this year, a 173 percent increase over the same period last year, according to the Cuban Embassy in Washington. During the same period, more than 240,000 Cubans traveled to the United States, an 84 percent increase, the embassy said.
The Trump administration preserved many Obama-era changes that eased travel, while assuming a more antagonistic posture toward Havana. Despite that, Cuban officials continued to woo American travelers.
The government has sought to persuade visitors that its hotel infrastructure will be in top shape by the winter, a peak travel season, despite the considerable damage that Hurricane Irma caused this month.
Cuba’s “commitment to you is not limited to recovering from the effects of the hurricane,” Tourism Minister Manuel Marrero Cruz said in the Communist Party newspaper Granma, “but that everything will be better than before and that we will have as a final result an updated and higher quality tourist product.”
That optimism stood in sharp contrast to the mood of Silvio Ortega and his wife, Julia de la Rosa, the owners of a bed-and-breakfast in Havana. The couple invested thousands of dollars in recent years to turn a bare-bones room rental business into a 10-room establishment with a pool and a stunning view of Havana.
After 2014, their client base, once mainly European, became increasingly American and upscale. “We watched the rise of American tourism with great optimism and enthusiasm,” Mr. Ortega, 60, said. That’s why news of the travel warning, which a reporter relayed during a phone conversation, landed like a thud. “I have the impression that the American people adhere to the laws and are reluctant to cross them,” he added.
Previous periods of deteriorating relations between the United States and Cuba have been characterized by tit-for-tat retaliation. On Friday, however, the Cuban government issued a restrained statement in response to the American announcement, suggesting it hoped to avert a further breakdown.
Josefina Vidal, a senior Cuban diplomat, called Washington’s reaction “hasty” and warned that it would “affect the bilateral relations, specifically the cooperation in matters of mutual interest.” But she said Cuba was committed to determining the cause of the symptoms experienced by the American diplomats.
The mysterious health problems have triggered a flurry of theories among Cubans. Some think a third country may have targeted diplomats with a sophisticated weapon. Others have suggested that groups of Cubans opposed to improved relations — be it exiles or hard-line Cubans on the island — could be to blame.
“It’s not a secret that there are sectors that need an enemy, and perhaps now they are finding a way to return to the past,” said Mr. Cárdenas, whose blog, La Joven Cuba, gave voice to a generation loyal to, but diplomatically critical of, the Castro government. “In Cuba, there is a sector that considers improved relations with the United States a betrayal.”
Ms. Vilches, the restaurant entrepreneur, said she hoped Americans would not be deterred from visiting Havana. She said she has enjoyed meeting inquisitive Americans at her restaurant, which is decorated with furniture that evokes the 1950s. But if there is a drop in American travelers, who these days make up 30 to 40 percent of her clients, Cubans will make do, she said.
“At the end of the day, we’ve become used to being blocked in several ways,” Ms. Vilches said.
Others were less stoic. Rocio Diaz, 28, a travel guide who works mainly with American visitors, spent part of Friday morning filling out an American visa application at an outdoor park with wireless internet in downtown Havana. Ecstatic after receiving an email from the State Department confirming that her petition had been received, she raced home to find her father crestfallen.
“What luck you have,” he told her, shrugging. Ms. Díaz said she dreamed of visiting the United States to understand her clients.
“I don’t know what my backup plan is,” she said. “My clients are Americans and it makes sense to go to America to understand their culture — not Europe or Central America.”