The new case brings to 14 the number of Canadians - alongside 25 Americans - who have reported unexplained symptoms from dizziness, fatigue, headaches, hearing and vision complications, to loss of balance, nausea and an inability to concentrate.
After recording over two dozen, still unexplained cases of illness, the United States embassy reduced personnel to a skeleton staff and stopped providing services to Cuban citizens who must now go to third countries for visa interviews.
Cuban officials have offered their full cooperation in investigating the mysterious illness since the first cases surfaced in the spring of 2017, officials said.
Canada's foreign office said the number of staff will now be cut by up to half as a result.
That individual reported health concerns on December 29 and was sent for immediate medical testing, which confirmed symptoms similar to those experienced by the others: dizziness, headaches, hearing and visual problems and fatigue.
However, Canada will still have an embassy in Havana headed by an ambassador and full consular services will be available to Canadians in Cuba.
"This behavior favors those who in the United States use this issue to attack and denigrate Cuba", Vidal said.
Ottawa is cutting the number of Canadian diplomats posted to the Canadian embassy in Havana, where Canadian diplomats and their families have experienced unusual ailments since early 2017.More news: Best Frenemies: Chris Christie and Donald Trump
The illness, which has affected both US and Canadian diplomats, causes dizziness, headaches and difficulty concentrating.
The Cuban government has denied any involvement in the incidents.
"I think I can safely say the Cuban officials are as frustrated as we are that we cannot get any closer to determining a cause", the Canadian Government official told reporters.
More than a million Canadians visit the island each year. All affected people will continue to receive medical attention, as required.
Canada's embassy in Havana, Cuba.
The US withdrew most of its non-essential diplomatic staff in September 2017 but Canada did not.
The US has not said what caused the incidents, although initial speculation centred on some type of sonic attack.
"A further reduction in the footprint is deemed to be the appropriate response given that these recent confirmed cases demonstrate that these incidents are still ongoing", an official said Wednesday, one of two who briefed reporters on condition they not be identified.