'I recovered from Sepsis but it turned my finger black'
More than 44,000 people die from sepsis in the UK each year, but that not many people know what it is.
It kills more people than bowel, breast and prostate cancer combined.
During the 2015 Christmas holiday, Ellie Mayling was diagnosed with the infection.
"I felt really ill. I was shivering and my teeth were chattering when it wasn't even cold," the 19-year-old tells Newsbeat.
Ellie says she then began vomiting but thought food poisoning was the cause.
"My mum noticed that I had a mottled rash all over my body," she remembers. She immediately thought it was meningitis.
Her mum thought it was meningitis too so Ellie was taken to hospital where she was diagnosed with sepsis - something she'd never heard of.
That's where things got a bit scary.
"In hospital my right index finger turned black," Ellie explains.
"The doctor said it would either self-amputate or it would heal itself.
"The blood poisoning had caused the nerves in my finger to die."
Doctors were able to save her finger but she has since lost all feeling in it.
She remembers her body shutting down but because she was so ill she doesn't remember much more.
"When I came out of hospital I had to have six moths off, I had to drop out of college.
"I'm just really lucky that I survived it and recovered so well."
What are the symptoms?
The UK Sepsis Trust lists six things to watch out for:
- slurred speech
- extreme shivering or muscle pain
- passing no urine in a day
- severe breathlessness
- "I feel like I might die"
- skin mottled or discoloured