She thought it was just a cold. Her throat was sore, and she felt tired all over. But as JoAnn Barr got her son ready for school that morning in March, she started gasping for breath. Within a few hours, Barr was on a ventilator in intensive care, her blood pressure bottoming out, her kidneys failing.

For a month, the 41-year-old Westminster woman hovered near death, a victim of the fast-moving, often-lethal condition known as sepsis. It's an illness that rages through the victim's bloodstream, unleashing a fury of reactions that kill tissues and shut down organs.After years of frustration, doctors believe a new frontier might be opening in treating sepsis. Last year, large clinical trials showed the benefits of early intervention, and researchers hit on a drug that might reverse the illness' fatal course.

Yet sepsis remains one of the most devastating and humbling conditions in medicine. A third of the 750,000 Americans per year who develop sepsis will die, a toll that equals that of heart attacks, or of all deaths from breast, colon, prostate and pancreatic cancers combined.

And as in Barr's case, sepsis can move with a swiftness that is shocking. In hours or a few days, the illness can kill. Doctors have a saying for it: "Fine in the morning, dead in the evening."

"It's the most awful, scary thing to actually take care of," said Dr. Trish Perl, Johns Hopkins Hospital's epidemiologist. "You just watch people die, and it doesn't matter what you do."

Early symptoms subtle

With an aging population and more aggressive, invasive procedures driving up the number of sepsis cases - by about 90 percent in the past decade - treatment questions are becoming more urgent.

"It's a huge problem," said Dr. Carl B. Shanholtz, director of the medical intensive care unit at the University of Maryland Medical Center. "This is probably the most common diagnosis we take care of."

Unfortunately, the early signs are subtle and mimic many other conditions, so many patients dismiss it, as Barr did. Without a simple diagnostic test, physicians miss as many as a quarter of the cases.

Then, the illness explodes with symptoms including violent chills, delirium, a spiking fever or faintness. When Barr felt short of breath, she called a neighbor, but when they arrived at Carroll County General Hospital's emergency room 10 minutes later, Barr's blood pressure was so low she was almost unconscious.

Nurses and doctors raced to get antibiotics pumping into Barr. They tried to push up her blood pressure with fluid and medicines. But soon, as in 80 percent of patients with sepsis, Barr needed to be put on a ventilator.

"She just went straight downhill, like she was falling off a cliff," said her husband, Ray Barr. Just 24 hours before, JoAnn had been healthy, exercising every other day, working in disease prevention at Baltimore's health department, raising their 9-year-old son, Ian. Now, she was hooked up to at least eight IV pumps, and she was so swollen from fluids that her hospital bracelet was embedded in her wrist. Feeling like she was suffocating on the ventilator, she frantically scribbled on a piece of paper, "I can't breathe."

Then she lost consciousness. It would be weeks later, after a transfer to the University of Maryland, before she would wake up again, and eventually recover.

Sepsis starts out simply enough, with an infection.

An otherwise-healthy person can get pneumonia, a urinary tract infection, gall bladder disease or diverticulitis. Barr had a group A strep infection in her throat that traveled to her lungs, causing pneumonia. People who are in car accidents or suffer burns or undergo medical procedures might get staph or other infections. Or most commonly, the elderly, or those with weakened immune systems, like cancer or AIDS patients, contract an infection.

Most of the time, a person is able to fight the infection and keep it from spreading. But in sepsis, the infection moves into the bloodstream, probably because of factors including the type of germ, the patient's immune system health, and even his or her genes.

Once the bacteria get into the blood, the body launches an overwhelming, system-wide counterattack. Blood vessels become inflamed, and their cell walls leak fluid. The body's clotting system goes awry, simultaneously causing bleeding and throwing clots that block the tiny blood vessels that feed organs.

One by one - or sometimes all at once - tissues start to die, organs fail. It can happen in a day or over weeks. In septic shock, the patient's cardiovascular system shuts down. One author described sepsis in 1881 as "the rude unhinging of the machinery of life," said Dr. Gordon R. Bernard, a Vanderbilt University professor of medicine and founding chairman of the International Sepsis Forum. That's an apt description, Bernard noted, because "everything falls apart."

Said Dr. Steven Johnson, chief of the division of critical care at Maryland Shock Trauma Center: "There are some bacteria that can take somebody who is normal at lunch time, and by dinner time that evening, they'll be in a situation where the mortality rate is more than 50 percent."