The deadly medical mystery that rocked Panama last September began innocuously, with a trickle of patients complaining of weakness and tingling in their legs. Within a matter of weeks Panama was grappling with a health crisis that claimed scores of lives until inspired sleuthing by a University of Miami-trained physician brought the dying to an end.

Nestor Sosa, M.D., brilliantly fulfilled the promise that gained him entry into the Miller School’s prestigious William J. Harrington Medical Training Programs for Latin America, currently celebrating its 40th anniversary. A Harrington trainee in the late 1980s, Sosa “was one of our best and brightest,” says Mark Gelbard, M.D., associate professor of medicine.

Sosa, 45, has received international acclaim for discovering that diethylene glycol, a poisonous substance used in antifreeze, was unwittingly mixed into 260,000 bottles of Panamanian cough medicine. The diethylene glycol was manufactured in China, where it had been labeled 99.5 percent pure glycerin, a sweet compound used in foods and drugs. Both substances are sweet-tasting and viscous.

Prior to the deaths in Panama, unscrupulous Chinese businessmen had knowingly substituted diethylene glycol for more expensive glycerin in other countries, with deadly results.

That wasn’t on Sosa’s mind in September, when patients experiencing weakness and tingling in their legs began showing up at the Panama City hospital where he worked as an infectious diseases specialist. The facility, Caja de Seguro Social/Complejo Hospitalario Metropolitano, is part of Panama’s social security system. Sosa was asked to investigate the malady, which medical researchers had erroneously identified as Guillain-Barré syndrome, a rare neurological disorder.

That’s because the initial stages of diethylene glycol poisoning mimic Guillain-Barré syndrome, an often fatal autoimmune disease with no known cause or cure. But Guillain-Barré was quickly ruled out when the patients in Panama began to also suffer kidney failure. By early October the death toll was in the low teens before eventually peaking at a reported 426 fatalities.

In the midst of a desperate search for a killer, Panama’s Health Ministry declared a national epidemic. Sosa notified officials at his hospital that the mysterious malady was killing roughly half its victims, and the Panamanian government asked him to establish and lead a medical task force.

Because 19 of the 21 patients who came to his hospital were older men, Sosa wondered if aphrodisiacs might be behind the deaths. But that hunch didn’t pan out. Most of the deceased were over 60 and suffered from hypertension and diabetes. Half had been taking a blood pressure drug called lisinopril, so as a precaution Panamanian pharmacies were banned from dispensing the medication. However, tests showed the drug to be safe.

Sosa’s tenacity finally began to bear fruit following the admission of a heart attack victim to his health care facility. While hospitalized, the patient came down with the mysterious ailment.

“It was obvious that whatever was causing his problems had to be on the medication list,” Sosa says.

The patient had been administered several drugs, including lisinopril. One of its potential side effects is a persistent cough. A short time afterward, Sosa heard of a patient in a private Panamanian hospital who’d presented Guillain-Barré symptoms after being given lisinopril.

“What really broke the case was when Nestor heard about that patient who wasn’t in the social security system,” says Gordon Dickinson, M.D., professor of medicine and chief of infectious diseases at the Miller School. “When that patient showed up, Nestor jumped in his car and went to interview this patient in another hospital.”

While there, he noticed a half-empty bottle of cough syrup issued through the social security system. “He didn’t belong to the social security health care system, but he wanted to save money, and the syrup was free,” Sosa recalls.

On October 10, 2006, Sosa arranged for several bottles of the cough syrup to be flown to the United States, where they were analyzed by the Centers for Disease Control and Prevention in Atlanta. The following day, United States health care officials informed Panama that the cough syrup had been contaminated with diethylene glycol.

Successfully tracking down the killer that terrorized Panama filled Sosa with mixed emotions. “I was happy because we found the cause, and we knew that was the beginning of the end,” he says. “On the other hand, we knew it was something we had manufactured, that had actually been made in a lab in my hospital.”

The Panamanian cough syrup tragedy triggered an uproar among a citizenry already furious with a social security health care system infamous for not having enough medication and long waiting lists for surgeries.

“This was a major blow to the social security system,” Sosa says. “There is an investigation going on that’s not finished, along with a public outcry to take out the minister of health. Because of the notoriety from this I got another job.”

After working for Panama’s social security health care system for 14 years, on April 1 Sosa took a position training Central American health care workers. Panama’s social security system claims 79 people died and 119 were affected by the adulterated cough syrup. The Panamanian district attorneys’ office, however, puts the death toll at 426.

Sosa’s role in identifying diethylene glycol as a mass killer is the crowning achievement thus far in a life marked by an uncompromising quest for excellence.

Born in Camaguey, Cuba, Sosa and his family moved to Panama when he was 9. He enrolled in the University of Panama in 1980 and graduated six years later with a medical degree. A knack for chess resulted in him being named a national master of chess in 1982 and national chess champion of Panama the next year.

Following graduation from the University of Panama, Sosa completed an internship at his former place of employment, Caja de Seguro Social/Complejo Hospitalario Metropolitano, followed by a month-long clinical rotation at the Copenhagen Komune Hospital, where he focused on internal medicine. Thinking several steps ahead, like the chess master he is, Sosa thought it would be useful to train at UM under the auspices of The William J. Harrington Medical Training Programs for Latin America. Sosa did three years of residency training followed by a two-year fellowship in infectious diseases. Gelbard, who directed the Harrington residency program when Sosa attended, recalls that he “was curious and had a thirst for knowledge.”

Attributes that would save untold numbers of Panamanian lives.