1 in 5 deaths caused by a disease you've never heard of

It might not be a household name, but it's deadly -- and common.

One in five deaths around the world is caused by sepsis, according to research published the week in the Lancet.

The life-threatening condition is caused by the body's response to infection, according to the Mayo Clinic, and it's sometimes referred to as blood poisoning.

People with chronic disease, older adults, young children, pregnant women and those with weakened immune systems are particularly at risk.

Among 56 million reported deaths in 2017, about 11 million were from sepsis, the study showed.

Because sepsis tends to occur in people in poor health, it's typically "been considered an intermediate rather than an underlying cause of death," which means it's likely to have been undercounted, according to commentary published in conjunction with the study.

To arrive at the new numbers, researchers analyzed more than 100 million death certificates from 1990 to 2007, concluding that sepsis is twice as common as previously thought.