What Is Havana Syndrome? Kamala Harris Singapore Trip Slightly Delayed Over Suspected Case

U.S. Vice President Kamala Harris' trip from Singapore to Vietnam faced a slight delay Tuesday after the discovery of a "recent possible anomalous health incident," according to the U.S. Embassy in Hanoi.

The "anomalous health incident" refers to an affliction called "Havana syndrome," an obscure string of health occurrences first documented in late 2016 by American diplomats and other government workers in Havana, the Associated Press reported. It is unknown at this time who and how many people may be experiencing the ailment in Hanoi.

Havana syndrome symptoms can include sudden pain and pressure in the head and ears, inexplicably hearing a loud noise, nausea, confusion and disorientation, according to reports compiled by WebMD. Complications from the syndrome, which can also cause headaches, fatigue, anxiety and varying levels of memory loss, have caused some Americans stationed in other countries to withdraw from active service, The Washington Post reported.

Health professionals have yet to determine a cause for the mysterious ailment, though some people have theorized that the syndrome is caused by targeted microwaves or sonic attacks.

Americans working diplomatic posts in other countries outside the U.S., including Germany, Austria, Russia and China, have reported similar inexplicable health incidents since the initial reports in 2016. There were also at least two potential cases documented in the Washington area, including one near the White House, the Associated Press reported.

For more reporting from the Associated Press, see below.

Harris' Singapore Trip
Vice President Kamala Harris' trip from Singapore to Vietnam was delayed slightly Tuesday as the U.S. Embassy in Hanoi reported a possible occurrence of Havana syndrome. Harris departs Singapore for Vietnam on August 24. Evelyn Hockstein/Pool Photo via AP

Harris was set to depart for Hanoi on Tuesday evening after delivering a speech in Singapore, castigating China for its incursions into the South China Sea, and a discussion of supply chain issues with business leaders.

But the flight was delayed for more than three hours and Symone Sanders, Harris' chief spokesperson, refused to explain. Unprompted, Sanders volunteered that Harris was "well" although reporters had seen the vice president several times Tuesday and had no reason to be concerned about her health.

Congress has raised alarms over such attacks, finding rare bipartisan support in House and Senate for continued government-wide investigation into the syndrome, response as well as millions in support for American personnel medical monitoring and treatment.

The Biden administration is facing new pressure to resolve the mystery as the number of reported cases of possible attack has sharply grown. But scientists and government officials aren't yet certain about who might have been behind any attacks, if the symptoms could have been caused inadvertently by surveillance equipment—or if the incidents were actually attacks.

Whatever an official review concludes could have enormous consequences. Confirmation that a U.S. adversary has been conducting damaging attacks against U.S. personnel would unleash calls for a forceful response by the United States.

For now, the administration is providing assurances that it takes the matter seriously, is investigating aggressively and will make sure those affected have good medical care.

One key analysis identified "directed, pulsed radio frequency energy" as the most plausible culprit. Published in December by the National Academy of Sciences, the report said a radio frequency attack could alter brain function without causing "gross structural damage." But the panel could not make a definitive finding on how U.S. personnel may have been hit.

And a declassified 2018 State Department report cited "a lack of senior leadership, ineffective communications, and systemic disorganization" in responding to the Havana cases. The report says the cause of the injuries was "currently unknown." The document was published by George Washington University's National Security Archive.

Chris Miller, the acting defense secretary during the last months of the Trump administration, created a Pentagon team to investigate the suspected attacks. That was after he met a soldier late last year who described how, while serving in a country Miller wouldn't identify, he had heard a "shrieking" sound and then had a splitting headache.

Harris Gives Speech in Singapore
Vice President Kamala Harris's trip to Vietnam was delayed because of possible Havana syndrome. takes questions from reporters as she visits the Flower Dome at Gardens by the Bay, following her foreign policy speech in Singapore, Tuesday, August 24. Evelyn Hockstein/Pool Photo via AP