In early June 2012, the Cuban Ministry of Health, citing a 19-year-old Cuban casualty, announced that a recently discovered neurological condition known as “halium 210” had caused his death. In fact, Cuban health officials suggested, it was caused by microwave exposure.

The virus had a particularly acute, devastating effect on military personnel. Thousands had undergone treatment for symptoms including memory loss, slurred speech, and lack of coordination. But forensic tests commissioned by the New England Journal of Medicine found no evidence to support the virus’s role in the deaths.

Other doubts had been raised. For instance, it had never been previously identified in humans, and researchers have never found a lab could produce vibrio cholerae, which is believed to have caused the illness. Yet strains of vibrio were found in Cuba’s wastewater after the announcement. So were strains of another neurodegenerative disorder, Guillain-Barre syndrome. There was also uncertainty about whether patients who initially reported symptoms were really affected.

Amid all this uncertainty, there had not been a systematic analysis of the possible causes of the neurological symptoms in Cuba, said Carmen González of the Naval Postgraduate School, a co-author of a recent report on the investigation into the illness. Her analysis was triggered by Pentagon-approved military personnel who sought medical diagnosis and treatment after visiting Cuba on August 1, 2011. Scientists subsequently sent blood samples to the United States Air Force Medical Research Institute for Genetic Analysis and Analysis at Dover Air Force Base in Delaware.

Among some of the evidence González cited were the fact that there were no studies, conducted with similar materials, investigating laboratory-produced neurodegenerative diseases, such as Guillain-Barre, even though other ailments were studied. Also, her report includes more information about the type of illness—shorter neurological symptoms—suggesting that this was a different kind of attack. And, it cited a Secret Service report regarding the health of some local FBI agents in Havana after they returned from Havana after touring the region where the illnesses were being reported. (It did not mention the name of the agent)

The most recent U.S. Centers for Disease Control and Prevention report found no biological organisms were present in the Havana shower taps. The agency offered no explanation as to why those water samples had been contaminated in the first place, though, and what controls could be implemented to prevent such contamination.