Most Americans have never heard of it, but according to recent federal data, sepsis is the most expensive cause of hospitalization in the U.S., and is now the most common cause of ICU admission among older Americans.

Sepsis is a complication of infection that leads to organ failure. More than one million patients are hospitalized for sepsis each year. This is more than the number of hospitalizations for heart attack and stroke combined. People with chronic medical conditions, such as neurological disease, cancer, chronic lung disease and kidney disease, are at particular risk for developing sepsis.

And it is fatal. Between one in eight and one in four patients with sepsis will die during hospitalization – as most notably Muhammad Ali did in June 2016. In fact sepsis contributes to one-third to one-half of all in-hospital deaths. Despite these grave consequences, fewer than half of Americans know what the word sepsis means.

What is sepsis and why is it so dangerous?

Sepsis a severe health problem sparked by your body's reaction to infection. When you get an infection, your body fights back, releasing chemicals into the bloodstream to kill the harmful bacteria or viruses. When this process works the way it is supposed to, your body takes care of the infection and you get better. With sepsis, the chemicals from your body's own defenses trigger inflammatory responses, which can impair blood flow to organs, like the brain, heart or kidneys. This in turn can lead to organ failure and tissue damage.

At its most severe, the body's response to infection can cause dangerously low blood pressure. This is called septic shock.

Sepsis can result from any type of infection. Most commonly, it starts as a pneumonia, urinary tract infection or intra-abdominal infection such as appendicitis. It is sometimes referred to as "blood poisoning," but this is an outdated term. Blood poisoning is an infection present in the blood, while sepsis refers to the body's response to any infection, wherever it is.

Once a person is diagnosed with sepsis, she will be treated with antibiotics, IV fluids and support for failing organs, such as dialysis or mechanical ventilation. This usually means a person needs to be hospitalized, often in an ICU. Sometimes the source of the infection must be removed, as with appendicitis or an infected medical device.

It can be difficult to distinguish sepsis from other diseases that can make one very sick, and there is no lab test that can confirm sepsis. Many conditions can mimic sepsis, including severe allergic reactions, bleeding, heart attacks, blood clots and medication overdoses. Sepsis requires particular prompt treatments, so getting the diagnosis right matters.

The revolving door of sepsis care

As recently as a decade ago, doctors believed that sepsis patients were out of the woods if they could just survive to hospital discharge. But that isn't the case – 40 percent of sepsis patients go back into the hospital within just three months of heading home, creating a "revolving door" that gets costlier and riskier each time, as patients get weaker and weaker with each hospital stay. Sepsis survivors also have an increased risk of dying for months to years after the acute infection is cured.

If sepsis wasn't bad enough, it can lead to another health problem: Post-Intensive Care Syndrome (PICS), a chronic health condition that arises from critical illness. Common symptoms include weakness, forgetfulness, anxiety and depression.

Post-Intensive Care Syndrome and frequent hospital readmissions mean that we have dramatically underestimated how much sepsis care costs. On top of the US$5.5 billion we now spend on initial hospitalization for sepsis, we must add untold billions in rehospitalizations, nursing home and professional in-home care, and unpaid care provided by devoted spouses and families at home.

Unfortunately, progress in improving sepsis care has lagged behind improvements in cancer and heart care, as attention has shifted to the treatment of chronic diseases. However, sepsis remains a common cause of death in patients with chronic diseases. One way to help reduce the death toll of these chronic diseases may be to improve our treatment of sepsis.

Rethinking sepsis identification

Raising public awareness increases the likelihood that patients will get to the hospital quickly when they are developing sepsis. This in turn allows prompt treatment, which lowers the risk of long-term problems.

Beyond increasing public awareness, doctors and policymakers are also working to improve the care of sepsis patients in the hospital.

For instance, a new sepsis definition was released by several physician groups in February 2016. The goal of this new definition is to better distinguish people with a healthy response to infection from those who are being harmed by their body's response to infection.

As part of the sepsis redefinition process, the physician groups also developed a new prediction tool called qSOFA. This instrument identifies patients with infection who are at high risk of death or prolonged intensive care. The tools uses just three factors: thinking much less clearly than usual, quick breathing and low blood pressure. Patients with infection and two or more of these factors are at high risk of sepsis. In contrast to prior methods of screening patients at high risk of sepsis, the new qSOFA tool was developed through examining millions of patient records.

Life after sepsis

Even with great inpatient care, some survivors will still have problems after sepsis, such as memory loss and weakness.

Doctors are wrestling with how to best care for the growing number of sepsis survivors in the short and long term. This is no easy task, but there are several exciting developments in this area.

The Society of Critical Care Medicine's THRIVE initiative is now building a network of support groups for patients and families after critical illness. THRIVE will forge new ways for survivors to work with each other, like how cancer patients provide each other advice and support.

As medical care is increasingly complex, many doctors contribute to a patient's care for just a week or two. Electronic health records let doctors see how the sepsis hospitalization fits into the broader picture – which in turn helps doctors counsel patients and family members on what to expect going forward.

The high number of repeat hospitalizations after sepsis suggests another opportunity for improving care. We could analyze data about patients with sepsis to target the right interventions to each individual patient.

Better care through better policy

In 2012, New York state passed regulations to require every hospital to have a formal plan for identifying sepsis and providing prompt treatment. It is too early to tell if this is a strong enough intervention to make things better. However, it serves as a clarion call for hospitals to end the neglect of sepsis.

The Centers for Medicare & Medicaid Services (CMS) are also working to improve sepsis care. Starting in 2017, CMS will adjust hospital payments by quality of sepsis treatment. Hospitals with good report cards will be paid more, while hospitals with poor marks will be paid less.

To judge the quality of sepsis care, CMS will require hospitals to publicly report compliance with National Quality Forum's "Sepsis Management Bundle." This includes a handful of proven practices such as heavy-duty antibiotics and intravenous fluids.

While policy fixes are notorious for producing unintended consequences, the reporting mandate is certainly a step in the right direction. It would be even better if the mandate focused on helping hospitals work collaboratively to improve their detection and treatment of sepsis.

Right now, sepsis care varies greatly from hospital to hospital, and patient to patient. But as data, dollars and awareness converge, we may be at a tipping point that will help patients get the best care, while making the best use of our health care dollars.

This is an updated version of an article originally published on July 1, 2015 on The Conversation, and updated on June 7, 2016. You can read the original version here.

Theodore Iwashyna, Ph.D., M.D., also contributed to this report.