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Canadian officials said the ongoing problems are raising concerns about a new type of acquired brain injury, the cause of which remains unknown.
As a favourite tourist destination for Canadians, Cuba annually attracts more than 1 million tourists, and Global Affairs Canada says there is no evidence of any related ailments among Canadian travellers.
The US personnel in Havana also took ill. Over 20 US envoys and their family members in the Caribbean nation suffered symptoms such as hearing loss, tinnitus, vertigo, headaches and fatigue since the incidents were first reported in November 2016.
The symptoms have developed amid concern about possible "acoustic attacks" in 2016 and 2017, which was regarded by Cuba as an unacceptable accusation without evidence.
"According to the specialists, medical information raised concerns for a new type of acquired brain injury. Additional research is needed to better understand this," said a statement issued by the ministry on Monday.
Canadian officials said Monday that the theory of an acoustic or sonic attack has been ruled out.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)