Although this condition can affect people of any age, babies and young children are amongst the most vulnerable.
Sepsis is a medical emergency so it's important to be able to recognise the symptoms so that early treatment can be given.
Sepsis occurs when the immune system responds to an infection by attacking the body's own organs and tissues. This can cause inflammation of the blood supply to vital organs such as the heart, kidneys and brain.
If sepsis isn't treated quickly it can cause widespread organ failure and may even cause death.
The main cause of sepsis in babies and young children is infection by bacteria, although rarely it can be caused by viruses or fungi.
Infection in the lungs, urinary tract, skin and other organs can spread and lead to sepsis. Another way sepsis can happen is when a surgical operation is carried out. Bacteria gets into the body through the site of the surgical cut.
Sepsis can be hard to identify in newborns and young babies, so you should seek urgent medical advice if your baby has any of the symptoms below.
Symptoms that may indicate that your baby has sepsis include:
Your baby will be treated in hospital, where antibiotics will usually be given by a drip and a number of tests, including blood and urine tests will be carried out to confirm sepsis.
Other tests that may be required are a lumbar puncture, where a sample of spinal fluid is tested to see if the baby has meningitis and a chest X-ray to check for pneumonia.
Your baby may also be given additional fluids via a drip to keep her hydrated and medication to support her blood pressure and circulation. Sometimes a ventilator is needed to help a baby breathe.
If sepsis is treated early your child should make a full recovery.