Washington ? It’s one of the most intractable killers you’ve probably never heard of: Sepsis, an out-of-control reaction to infection that can start shutting down organs in mere hours.

A new push is beginning for hospitals to be more aggressive in rolling out care at the first hint of trouble — even as scientists discover an intriguing clue to what may fuel the deadly cascade estimated to kill more than 200,000 people a year in the U.S. alone.

There’s no simple diagnostic test for sepsis, but there are warning signs if health providers pay close attention, says Dr. James O’Brien, a critical care specialist at Ohio State University Medical Center.

“Minutes matter,” he adds, saying delays too often are “just an issue of not treating this like a medical emergency.”

Once misleadingly called blood poisoning, sepsis is the body’s overreaction in fighting an infection that in turn injures its own tissues, leading to shock and organ failure.

That doesn’t mean the infection has spread throughout the body — it doesn’t always, stresses sepsis specialist Dr. Kevin Tracey of the Feinstein Institute for Medical Research in New York, part of the North Shore-Long Island Jewish Health System. Instead, complex interactions between the microbe and the immune system make the latter run amok.

“At that point even if you eradicate the bacteria — we can do that most of the time — the damage continues to spread because of the toxic reaction that’s unleashed,” says Tracey, who helped lead a meeting of international sepsis experts last week who formed a “Global Sepsis Alliance” to urge more aggressive care.

Even people who’ve survived sepsis may not have heard the term, because it’s such a hard-to-explain concept that many doctors instead just say they battled a tough infection, Tracey says.

And the earliest symptoms that someone with an infection is sliding into sepsis are vague: Confusion, shortness of breath, an increase in heart rate, dropping blood pressure, weakness.

But the alliance’s goal: Start antibiotics and intravenous fluids, to counter the shock or low blood pressure, within an hour of suspicion of sepsis. Every hour of delay lowers survival by nearly 8 percent, yet many hospitals don’t get appropriate care started for four or even six hours, O’Brien told the meeting.