The number of NHS patients dying from sepsis has risen by more than a third in two years, a new study has found.

Data collected by Sir Brian Jarman, emiterus professor of primary health care at Imperial College London, reveal that there were 15,722 sepsis-related deaths in hospital or within a month of discharge in the year ending April 2017.

Sepsis is “the body’s overwhelming and life-threatening response to infection that can lead to tissue damage, organ failure, and death”, says advocacy organisation Sepsis Alliance.

Melissa Mead, whose baby son William died of sepsis following a chest infection in December 2014, has been campaigning for greater awareness of the condition. Mead, from Cornwall, said: “Whilst you have a lack of public awareness you are going to have people who are sitting at home, feeling poorly, and don't even realise that sepsis is even a thing.”

What is sepsis?

Sepsis is a severe and life-threatening illness caused by the body’s response to an infection. It develops “when the chemicals the immune system releases into the bloodstream to fight an infection cause inflammation throughout the entire body instead”, says information site Healthline.

There are three stages of sepsis, which is also known as bacteremia, or blood poisoning. The illness is classified as severe sepsis when signs of organ dysfunction are present, such as difficulty breathing, low or no urine output, abnormal liver tests, or changes in mental status. “Nearly all patients with severe sepsis require treatment in an intensive care unit (ICU),” says Sepsis Alliance.

Septic shock is the most severe level and is diagnosed when blood pressure drops to dangerous levels. It can result in gangrene and limb amputations, and has a 50% mortality rate.

Why are sepsis death rates soaring?

The author of the new report on sepsis deaths in NHS hospitals believes staff shortages and overcrowding on wards mean many cases are not being spotted quickly enough.

“The biggest thing that’s important seems to be the number of staff - doctors per bed. One of the important things is the overcrowding of hospitals. The level of overcrowding shouldn’t be more than 85% [bed occupancy], and it’s been going over 90% in recent years,” Sir Brian told the BBC’s Today programme.

He added: “The treatment for sepsis, if it’s caught early enough, involves very basic interventions - looking for the source of the infection, giving antibiotics.

“For every hour we delay in giving antibiotics, the patient’s risk of dying increases by a few per cent, so it’s essential that we spot it early and deliver the basics of care quickly.”

Responding to the findings, NHS England argued that more conditions were being classed as sepsis than before and that this was the reason for higher numbers.

A spokesperson said: “Over the past three years there has been huge effort across the NHS to increase clinical recognition of, and recording of, sepsis.

“That improved method of recording means some cases previously recorded as simple infections are now classified as sepsis. So this data does not prove an increase in sepsis cases per se.”