Dee sat down in a chair next to Lisa's bed, patted her daughter's swollen blue hand and began: "Our baby is beautiful," she said. "I can't wait for you to see her." Susan Heiner, uncertain that Dee understood the prognosis, warned her not to get her hopes up. "This is serious," she told her. Of course, said Dee. "But they don't know Lisa. Lisa won't stand for this."

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She was fighting a life-and-death battle against Streptococcus pyogenes — Strep A —a common one-cell organism that is mindless in its drive to survive. For that, it needs a human.

In winter months, about 1 in 20 adults and one-third of children carry Strep A in their noses, throats or on their skin at any time. It may hang around for a few days or even months, but most often it's benign. Since Strep A conjures the image of a sore throat, a mild skin infection, occasionally a more severe complication like rheumatic fever, it's easy to underestimate its destructive potential. There are about 150 different varieties, and it is singularly good at adapting to its circumstances.

In rare and horrifying cases — about 3.5 in 100,000, according to noted infectious disease expert Dr. Dennis L. Stevens of the VA Medical System in Boise — Group A Strep becomes vicious. Experts call it "invasive" when it works its toxic way into parts of the body usually out of its reach, like the blood, muscle or spinal fluid.

Invasive Strep A can directly cause necrotizing fasciitis, often simplistically called flesh-eating disease, although in reality it attacks connective tissue, destroying muscles and their underpinnings, not just flesh. One in five afflicted that way will die. It can also cause devastating syndromes, not by spreading bacteria but by releasing powerful poisons. The process can rage on after the bacteria itself has been killed — penicillin usually does the trick.

About a third of those cases turn into Streptococcal toxic shock syndrome (not associated with tampons). As blood pressure plunges, crucial organs like kidneys and lungs start to shut down. As many as 70 percent of patients die. Invasive Strep A may also jump-start a process of blood coagulation; the widespread clotting chokes off blood flow to the fingers and toes, arms and legs, strangling limbs. If the limbs die, they must be removed to save the rest of the body.

Lisa's strep chose three destructive paths, says Dr. Jeffrey R. Saffle, professor of surgery at the University of Utah School of Medicine and director of University Hospital's burn intensive care unit. It settled in the muscle and connective tissue in her abdominal wall, creating large abscesses. It triggered toxic shock. And it choked off circulation to her limbs.

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