"There's a sufficient amount of concern that with the number of cases that could affect our workforce that this might be a prudent step," a senior defense official said to CNN.
The State Department has already issued a memo on the issue, asking staff to immediately report any symptoms.
The first incidents were reported in 2016, when officials in Cuba reported feeling waves of pressure in their heads. Some of those affected said they head sounds similar to a swarm of cicadas that stopped when they opened a door to the outside, according to The New Yorker. Aftereffects included strong headaches, tinnitus, loss of vision and hearing, vertigo, brain fog and loss of balance and muscle control.
Other possible incidents were also reported in other locations, including Moscow. Over 130 possible cases of Havana Syndrome have so far been reported in Colombia, Kyrgyzstan, Uzbekistan, Austria and within the US, among other countries, according to The New Yorker.
One theory behind the syndrome is that Russia has been using microwave-radiation devices against US officials in order to collect intelligence from their computers and cell phones and the devices have been harming the targets as well. US intelligence has so far been unable to find any evidence to back this theory.
In multiple cases, officials reported symptoms alleviating after they changed location.
In one case, a junior White House staffer who had previously suffered from Havana Syndrome later noticed an SUV parked near her house and a man who seemed to be following her. When she stood across from him, she suddenly felt an intense pain in her head and heard a sharp ringing noise which was different than what she experienced in the first case.
The University of Pennsylvania's Center for Brain Injury and Repair used MRIs to study the brains of forty Havana Syndrome patients and found that while there was no sign of physical impact to the victims skulls, it seemed as if the victims had a "concussion without a concussion," according to The New Yorker, as the team found signs consistent with brain damage.A study carried out by Dr. Alon Friedman of Ben-Gurion University of the Negev and Dalhoisie University Brain Repair Center in Nova Scotia, Canada in 2019 found that Havana Syndrome was likely caused by the use of "pesticides and other toxins."
Some of the victims experienced lasting symptoms.
The CIA and other government bodies have reportedly been skeptical about the reported illness, with victims' claims being largely dismissed in past cases. That attitude appears to be changing, as a Senate committee reported in April that the number of suspected cases appears to be rising, according to CNN.
On Wednesday, NBC reported that State Department staffers had sent a letter to the State Department leaders demanding that the State Department start taking reports of Havana Syndrome more seriously.
Aaron Reich contributed to this report.