Excerpt from The Invisible People by Greg Behrman, plus links to reviews, author biography & more

As a young man fresh out of Southern Florida State College in the early 1960s, McCormick's church paid for him to spend a few years teaching science to youngsters in Zaire, formerly the Belgian Congo. He grew enamored with African culture and life, and the continent called McCormick back time and again in the decades to follow. Through it all, he had become intimately acquainted with Africa's vast equatorial plains and its dense northeastern jungles. He'd basked in the continent's natural splendor and he'd known its cruelty.

In 1976, he was summoned to Yambuku, Zaire, to investigate a virulent outbreak. Yambuku, McCormick would learn upon his arrival following a punishing trip from Kinshasa, the country's capital, was plunged into chaos and despair, struck with a viciously lethal virus that McCormick and his colleagues would later name after a nearby river: the Ebola.

He'd be called back to investigate yet another Ebola outbreak in 1979, this time in Africa's northeast region, in a similarly devastated town in the Sudan called Nzara. McCormick arrived in the Sudan with only one other colleague, lab technician Roy Baron, in tow. In short order, the two were directed to a makeshift hospital that seemed to McCormick more like a dank hut, in a nearby town called Yambio. The disease, transmitted through blood, is highly contagious and almost 100 percent lethal; there was no vaccine and no treatment. Wearing full body protective suits and peering through respirator face masks, the two looked out at a macabre spectacle of more than twenty patients writhing in agony. McCormick worked through most of the first night in unbearable humidity taking blood samples and conducting tests that would reveal the extent of the outbreak.

Two nights into the investigation, he tended to an elderly lady whose fever had spiked to dizzying heights. Seemingly delirious, she had recently suffered a seizure. She seemed to McCormick a textbook case. Wearing latex gloves, he inserted a needle into her frail arm and pulled back the syringe to draw out her blood. To McCormick's shock, she gave a powerful lurch. Stunned, it took him a few moments to realize that upon pulling back, he had stuck himself with the blood-filled syringe. His glove was ruptured. There was blood, and it was McCormick's. He had punctured himself.

A wave of nausea struck. He didn't panic, though. There was one possible measure he could take, even if it was a long shot. For years there had been some mumblings in scientific circles that transfusions of convalescent blood (blood from those who had recovered from Ebola) might help stem infection. McCormick had come to the Sudan armed with a few bags of the blood, extracted from these rare cases from Zaire, just in case.

That night, Baron gave McCormick a transfusion. They washed down the anxiety with more than half a bottle of whiskey. McCormick, sure that he was already dying, got back to work the following morning.

He soldiered on, conducting his investigation of the outbreak in the days that followed. A few days later, the woman's blood sample came back yellow -- she tested negative. He could breathe again. He felt, he would later tell friends and colleagues, as if he had been given his life back -- as if he'd won the lottery.

In the years to follow, McCormick would move from disease to disease, always chasing the next great outbreak. Usually, he would go to the outbreak. On this summer day in 1983, it had come to McCormick. As the Belgian doctor's offhand comment sank in, McCormick felt a familiar rush.

"How many patients do you have?" he asked Desmyter.

"About thirty," he remembered his colleague answering.

McCormick's deductive train of logic began generating steam. There was no way, he knew, that even 1 percent of the Zairean population could possibly afford the travel expenses to make it from Zaire to Belgium. If Desmyter was right, there weren't thirty cases in Zaire. There were thousands.

"All kinds of lightbulbs began flashing above my head," recalled McCormick, thunderstruck by the realization: AIDS was global.