"There has always been significant political tension between the USA and Cuban governments, but the experience that our travelers have had on the ground with the Cuban people has been nothing short of incredible".
At least 21 diplomats and family members have been affected.
Since the re-establishment of diplomatic relations in 2015, Cuba and the USA have been working together in areas including law-enforcement cooperation against drug-trafficking and human smuggling.
"We have it under evaluation", Tillerson said.
The Florida Republican early Friday questioned the logic of continuing to allow Cubans to remain in the United States but reducing the US embassy in Havana to emergency-only staff.
Airbnb spokesman Nick Papas said that "consistent with US law, our operations in Cuba will continue".
He spoke to reporters on the White House South Lawn after the State Department announced a sharp drawdown of USA personnel at the embassy. Still the move is a blow to Obama-era efforts to increase engagement and contact between the two former Cold War adversaries.
"The safety and security of all diplomatic personnel in Cuba, and anywhere in the world, is the first priority of our country", said James Williams, president of Engage Cub.
With so many questions swirling, Secretary of State Rex W. Tillerson met with Cuba's foreign minister Bruno Eduardo Rodríguez Parrilla in Washington a few days ago. The U.S. State Department warned U.S. citizens on September 29, 2017 not to visit Cuba.
Investigators have struggled to identify the source of the attacks as symptoms vary markedly from person to person.
Today's developments added two new factors to this diplomatic crisis: The US is now explicitly calling the episodes "attacks", and it's warning travelers that they could also be at risk.
The move to dramatically scale down embassy staff - which was reportedly ordered by Tillerson late Thursday - may indicate that the USA, which has so far avoided accusing the Cuban government, is now blaming it for the attacks, according to AP. Attacks took place in the diplomats' homes as well as hotels. U.S. citizens should not attempt to go to the U.S. Embassy as it suffered severe flood damage during Hurricane Irma.
He said the attacks have led to "a range of physical symptoms, including ear complaints, hearing loss, dizziness, headache, fatigue, cognitive issues, and difficulty sleeping". The most recent attack occurred in August, according to that report.
The visa component of the order will continue indefinitely, and Havana will see an embassy staff reduction of approximately 60%. Only "emergency personnel" will stay. "But I can't rule out the American public traveling in Cuba might (also) be at risk".
No American tourists have been harmed in the attacks, but there are concerns they could be exposed to danger if they travel to Cuba. The US embassy on the island, however, will stop processing regular visas. They say the steps will remain until Cuba can assure the USA its diplomats are safe.