Washington (CNN)When CIA Director Bill Burns traveled to India earlier this month a member of his team reported symptoms consistent with Havana syndrome and had to receive medical attention, according to three sources familiar with the matter.

 

The incident set off alarm bells within the US government and left Burns "fuming" with anger, one source explained. Some officials at the CIA viewed the chilling episode as a direct message to Burns that no one is safe, including those working directly for the nation's top spy, two sources said.

The event marks the second time in less than a month that reported cases of the mysterious illness have impacted the international travel of top Biden administration officials. Last month Vice President Kamala Harris's visit to Vietnam was slightly delayed when multiple US personnel reported symptoms consistent with the syndrome just ahead of her visit, and at least two of them had to be medevaced.

Under Burns and the Director of National Intelligence, Avril Haines, the intelligence community has undertaken a wide-ranging investigation into the mysterious attacks, including a 100-day probe into the potential causes that began earlier this summer. While that investigation is expected to be concluded before the end of the year the timeframe could be somewhat adjusted and there is no public report planned, two sources said.

"We don't comment on specific incidents or officers. We have protocols in place for when individuals report possible anomalous health incidents that include receiving appropriate medical treatment," a CIA spokesperson said. "We will keep doing everything we can to protect our officers."

The situation in India could have dramatic implications: the CIA director's schedule is tightly held and there are deep concerns among US officials about how the perpetrator would have known about the visit and been able to plan for such an aggression.

The person traveling with Burns who experienced the symptoms in India received immediate medical attention when they returned to the US, sources said.

Growing concern

US investigators have struggled to determine what or who is causing the mysterious symptoms, and how exactly they are doing it. Incidents of Havana syndrome began in late 2016 in Cuba and there have since been cases reported in Russia, China, Austria and other countries across the globe. CNN has previously reported that incidents also took place on US soil, including two staff members of then-President Donald Trump's national security council who were struck near entrance points to the White House.

The ongoing incidents have put US diplomats and intelligence officials on edge leading up to the UN General Assembly in New York this week where diplomats from around the world -- including many US diplomats -- will convene in close quarters. Only a handful of the total reported incidents have occurred on US soil, but the gathering in New York is always viewed as a target-rich environment for espionage.

President Joe Biden was recently updated on the overall situation -- including the fact that there are more than 300 possible cases, the kind of medical support being provided to those impacted, and the investigation into the matter that is led by the intelligence community.

Over the summer the Director of National Intelligence, Avril Haines, launched the 100-day investigation into the "mechanism" behind the incidents, and efforts that could be taken to defend against the attacks. Putting a timeframe on it was part of an effort to drum up the intensity of the investigative effort, but the deadline could be extended if that is needed, sources said.

There are also other ongoing investigations by the US intelligence community focused on the question of the perpetrator behind the incidents, which the US government calls anomalous health incidents or AHIs, and what the US can do to defend against these incidents.

The US government is "pursuing multiple lines of effort" to investigate the Havana syndrome, a CIA spokesperson said. The spokesperson added that one of those efforts is led by ODNI and CIA officers as well as the outside scientific community to "to work collectively to increase our understanding of the possible mechanisms that could be causing AHIs."

Since Biden took office his national security team has been keenly focused on probing the mysterious incidents and getting impacted US personnel the assistance they need.

Secretary of State Tony Blinken spoke with US diplomats affected by the Havana syndrome earlier this month which marked his first meeting with those impacted, according to a State Department Spokesperson. The conversation came after CNN reported of frustration among rank-and-file staffers about how the department had handled the mysterious incidents.

Lawmakers were initially critical of the Biden administration for not sharing regular updates on the mysterious incidents. But in recent months the administration, in an effort led by Burns, have made changes to the processes and support for those impacted and personnel working on those efforts.

"We've strengthened efforts to determine the origins of the incidents, including assembling a team of our very best experts -- bringing an intensity and expertise to this issue akin to our efforts to find bin Laden," a CIA spokesperson said. "The senior officer who leads the team spent more than a decade on counterterrorism issues and was a driving force in CIA's analytic and targeting work that led us to find bin Laden."

Still, the incidents have continued to occur, leaving US diplomats and US intelligence officers on edge as they take on new assignments overseas.