The State Department revealed Thursday that a second American citizen in China has suffered adverse health effects similar to those of an American diplomat in Shanghai and 26 diplomats in Havana, Cuba, part of a wave of attacks of unknown origin.

As many of those affected by the attacks have described hearing high-pitched noises and feeling pressure headaches before suffering a variety of symptoms ranging from dizziness to brain damage, many in the media have begun referring to them as “sonic” attacks.

The Trump administration has not revealed a source for these attacks – though the State Department changed its terminology from “incidents” to “attacks” late last year, while China and Cuba have denied any wrongdoing.

The victim identified Thursday is the first private citizen to suffer these effects in China; Reuters notes that 19 individuals traveling to Cuba contacted the U.S. government complaining of similar symptoms. In addition to the Americans, some reports suggest that Canadian diplomats in Cuba have complained of similar symptoms, despite warm relations between the communist Castro regime and the administration of liberal Prime Minister Justin Trudeau.

The State Department warned all U.S. citizens in May traveling to China to remain vigilant for any indication of symptoms like those suffered by diplomats in the two countries.

“Since the release of the first (Guangzhou-related) Health Alert on May 23, the Department of State has been contacted by one U.S. citizen who reported experiencing similar symptoms following travel to China,” a State Department official told Reuters. “This is an evolving situation. As we state in our health alert, if you have concerns about any symptoms or medical problems, consult a medical professional as soon as possible.”

The official did not clarify whether the State Department was certain the incident was related to those affecting U.S. and Canadian diplomats. It is also unclear where in China the traveler suffered these symptoms; the previously known case of these health effects occurred in Guangzhou.

While the State Department has confirmed only two cases of these attacks in China, it evacuated at least nine individuals from Chinese consulates in China as recently as late June, according to a Wall Street Journal report. In addition to these, another 250 people working at the U.S. consulate requested medical evaluations following the revelation of the Guangzhou case.

One of these workers, Mark Lenzi, went public with symptoms that he and his wife suffered while in Guangzhou and has requested further evaluation by U.S. medical authorities.

The first known instances of these attacks occurred throughout 2017; the most recent documented cases in Cuba surfaced in late June, the first since those confirmed in August 2017. In March – in between the confirmation of the older cases and the two new ones – the State Department issued a travel warning for U.S. citizens to Cuba calling those affected the “targets of specific attacks.”

Among the list of symptoms in that travel warning were “loss of hearing, dizziness, headaches, fatigue, cognitive problems, visual problems, and difficulty sleeping.”

Unlike China, which has issued limited statements vowing to cooperate with American authorities to find the root cause of these illnesses, the communist regime governing Cuba has responded to these cases with belligerence. While initially stating that Cuba would cooperate with American investigations, Havana’s top diplomats have instead shifted gears toward blaming the affected diplomats for their own illness. In October 2017, Cuba’s state television network and the official newspaper of the Communist Party, Granma, published a “report” concluding that the victims of the attacks had heard insect noises outside of their home and, not being native to tropical habitats, did not recognize the sounds. Cuban officials insisted that their adverse health effects were psychosomatic and the product of paranoia.

Four months later, the Journal of the American Medical Association (JAMA) published a study on the victims in Havana concluding that it would be impossible for these individuals to fabricate such an illness and that a phenomenon on unknown effect had indeed severely damaged their brains. The Castro regime has dismissed the study.

This month, two days before the State Department confirmed a 26th victim in Cuba, Granma published a piece insisting the attacks were “not real” and claiming the allegations “would be funny if the situation was not so serious and ill-intentioned.

Follow Frances Martel on Facebook and Twitter.