The spread of Havana syndrome has “dramatically hurt” morale in the US diplomatic corps and affected recruitment, according to the head of the American Foreign Service Association (AFSA).

Eric Rubin, whose association represents nearly 17,000 current and former diplomats and foreign aid workers, said it was getting harder to find young people to work abroad, because of concerns about Havana syndrome – and about whether the government would look after them if they got sick.

“People have suffered real trauma and real injury, and it has dramatically hurt our morale, our readiness, our ability to recruit new members in the foreign service,” Rubin told the first medical symposium on the syndrome since it began affecting US diplomats and intelligence officers in 2016, organised by the University of Texas Southwestern Medical Center.

The cause of the syndrome, which involves long-term loss of balance and cognitive function, remains a mystery. A report by a US intelligence panel of experts last week found that pulsed electromagnetic energy and ultrasound were plausible causes in at least some cases.

A CIA assessment made public last month however determined that the majority of the thousand possible cases reported were most likely not the result of a global campaign by a foreign power, while in some two dozen incidents the cause could not be explained.

Rubin did not speculate over the cause, but said that the syndrome was having a potentially serious effect on US diplomacy.

“It is getting harder when we recruit people,” the AFSA president said. “I’ve had young members of the cohort that’s coming into the foreign service ask me: ‘If I do this, what am I getting into? And is this going to get worse? Is this going to get solved? If I get attacked and if I get injured, who’s gonna be there for me?’

“We’ve got to address that,” Rubin said.

Rubin said that care was improving for US officials who have been affected, but that the AFSA was still encountering bureaucratic resistance.

“We pushed really hard,” he said. “We did succeed, but it’s still case-by-case.”

Kenneth Dekleva, a former state department medical officer and psychiatrist who is leading an effort at UT Southwestern to coordinate research on Havana syndrome, said that psychogenic explanations for the spread of the symptoms were not convincing.

“Most diplomats – I would say 99% – want to be overseas, they want to serve their country with dignity and honor, and they want to be healthy,” Dekleva told the Guardian. “They don’t want to assume a patient role. And there’s no gain from it. The burden of illness and suffering is very real for the people. And I find that compelling.”