Today - Friday 13 September - marks World Sepsis Day.
It's an important day to raise awareness of the condition, with events held on every continent around the world, including sports activities, dinners, exhibitions and social media campaigns.
Read on to find out more about it.
Sepsis is a medical condition which occurs when the body's immune system - which is meant to fight against disease and infection - starts to attack the body's own organs.
The NHS explains: "Sepsis can be triggered by an infection in any part of the body. The most common sites of infection leading to sepsis are the lungs, urinary tract, tummy (abdomen) and pelvis."
It can be difficult to diagnose as the symptoms can at first appear to be flu, gastroenteritis or a chest infection. They may take the form of unusual breathing, a physical rash or a change in skin's appearance (for example, it is blotchy or paler).
The fact that sepsis can be difficult to diagnose is a problem because it's really important to do it as early as possible and for the patient to start taking antibiotics to treat it.
You cannot catch sepsis from someone else.
Sepsis is often diagnosed using basic measurements such as temperature, heart rate and breathing rate, as well as a blood or blood pressure test.
In February 2019, it was announced that a new test for quicker diagnosis of sepsis had been developed by researchers at the University of Strathclyde.
This was important news as the condition is not always easy to detect.
The device used in the new low-cost test examines the patient's blood and is able to give a result in 2.5 minutes.
At the moment, it can be tricky to diagnose the condition, but the new test would enable doctors and nurses to quickly test for the condition themselves - at a patient's bedside in hospital, in A&E departments or at doctors' surgeries, for example.
Not only that, but at the moment blood tests to work out exactly the right antibiotic for the patient can take three days, so this new test could prove revolutionary, as it will provide this information much quicker.
It can also be used to monitor sepsis levels, so doctors can work out the right treatment for those who are ill.
Researchers say it is hoped that it will be possible to use this test for everyday diagnoses in three to five years.