A CIA officer who was traveling with agency director William Burns to India this month reported symptoms consistent with Havana syndrome, CNN and the New York Times reported on Monday.
The victim, who was not identified, had to receive medical attention, CNN reported, citing unnamed sources.
A disease —considered to be mysterious so far, 'Havana Syndrome' has left several US diplomats plagued with severe headaches, nausea, and possible brain damage.
The condition, which seems to have almost uniformly affected US officials, has sparked several theories — from a 'microwave attack' to weapons that focused on ultrasound, poison, and even a reaction to crickets.
The circumstances of the incident are still being investigated, and officials have not yet determined whether the CIA officer was targeted because the officer was traveling with the director, William Burns, or for other reasons. If the incident was caused by an adversarial intelligence service, it may not have known the officer was traveling with Burns.
Officials have struggled to determine the cause of the symptoms. While some officials are convinced they are attacks and that one or more rival powers are responsible, intelligence agencies have yet to come to any firm conclusions.
The incident in India was reported earlier by CNN. Burns has made investigating the anomalous health incidents attributed to Havana syndrome a top priority, creating a targeting cell to investigate the incidents and improving medical care for those who have been injured by them.
Nearly half of the known cases involve CIA officers, although State Department diplomats and members of the military have also been affected, officials have said.
Last month, Vice President Kamala Harris was delayed for three hours as she was about to fly to Hanoi, Vietnam, after a U.S. official in Vietnam reported Havana syndrome symptoms.
Current and former officials said there is no sign of the incidents trailing off, and some people believe they could be increasing.
While some officials believe the incidents could go back years, including to the Cold War, the most recent spate began at the U.S. Embassy in Havana, where diplomats and CIA officers reported hearing strange sounds and then feeling headaches and nausea.
That was followed by a series of incidents at U.S. diplomatic outposts in China that left a number of U.S. officials badly injured. Since then, cases have been reported throughout Asia and Europe.