Far more people in the UK suffer from deadly sepsis than previously thought, research shows.
A study from the York Health Economics Consortium suggests 260,000 Britons develop the condition every year.
This is 110,000 higher than previous estimates, which put the number of affected patients at 150,000.
Sepsis is a life-threatening condition that occurs when the body's immune system goes into overdrive as it tries to fight an infection. It must be treated quickly with antibiotics.
Early symptoms include fast breathing or a fast heartbeat, high or low temperature, chills and shivering. Sufferers may or may not have a fever.
Severe symptoms can develop soon afterwards and include blood pressure falling low, dizziness, disorientation, slurred speech, mottled skin, nausea and vomiting.
The condition hit the headlines following the death of 12-month-old William Mead in December 2014.
NHS doctors repeatedly failed to spot he had sepsis, while 111 also mishandled a call from his mother Melissa.
Another child, three-year-old Sam Morrish, from Devon, died from sepsis in December 2010.
He was the victim of a catalogue of NHS errors, including how his call was handled by NHS Direct, now replaced by the 111 service.
Call-handlers at NHS Direct failed to categorise Sam's mother's call as urgent, despite indications that his vomit contained blood.
Even when hospital staff finally realised he was critically ill, they waited three hours before administering the antibiotics that could have saved his life.
Dr Ron Daniels, chief executive of the UK Sepsis Trust, said deaths in the UK every year may be as high as 65,000.
The new study also found that the cost of sepsis to the UK economy is likely to be as much as £15.6 billion every year, rather than the £2.5 billion previously estimated.
Dr Daniels said: "We've long been aware that sepsis causes thousands of unnecessary deaths every year and presents an unmanageable economic burden.
"A crippling paucity of data has thus far confined us to conservative estimates, but the figures reported in YHEC's study are a shocking new indication of the gravity and sheer scale of the problem. It's sobering to learn that the issue is so much greater than previously estimated.
"Equally sobering, though, is the dearth of reliable data recorded for a condition that carries such an overwhelming costs in human and economic terms.
"It's imperative that the Government acts decisively to develop a national 'sepsis registry' and introduces coding practices for sepsis in all NHS trusts.
"A precise understanding of how the NHS handles sepsis is urgently required to prevent avoidable deaths, improve outcomes for survivors and save billions of pounds for the UK as a whole."
Health Secretary Jeremy Hunt said: "We need to get far better at spotting sepsis across the NHS, which is why we are rolling out a lifesaving campaign to raise awareness and improve clinical practice.
"Already a million leaflets and posters have been distributed to GP clinics, hospitals and other public places - another step in our fight against this devastating condition."?