Scientists are a step closer to working out what is causing a mysterious polio-like illness which struck and paralysed hundreds of children in the UK and US last year.
New research has proven an already-known virus caused at least one case of acute flaccid myelitis (AFM), a potentially-deadly nerve-damaging illness.
AFM was last year diagnosed in at least 228 people in the US and 28 in the UK, many of them young children.
The incurable illness is crippling and often leaves patients with paralysed arms and legs.
But doctors and scientists have been puzzled by the condition, struggling to understand what causes it and only being able to spot it once symptoms start.
Chloe Stevenson, a three-year-old from Plymouth, Devon, has spent months receiving hospital treatment being left with a paralysed left arm after developing acute flaccid myelitis, a rare and poorly understood condition which can cause devastating nerve damage
At her worst, Chloe could only wake up for five minutes at a time because she was so tired, her mother Ms Carter said, but her condition has steadily improved since she fell ill in the autumn
Scientists at the University of Minnesota and the US's Centers for Disease Control and Prevention believe enterovirus-D68 (EV-D68) may be causing the illness.
They found the virus in the spinal fluid of one out of six children who got AFM, and they could prove it caused the illness, Minnesota's Star Tribune reported.
'The fact that we were able to definitively identify the EV-D68 virus as the cause of paralysis in one of our Minnesota patients does suggest this virus as a probable cause in our other recent AFM cases,' said Dr Heidi Moline, the study author.
EV-D68 had been found in the spinal fluid of another patient in California before, but the sample was contaminated so the evidence couldn't be used.
This, Dr Moline said, is the first 'true confirmation' of it causing the disease.
The virus was first recorded in patients in the US in 1987 but numbers were low. It has become increasingly common over time but is hard to keep track of.
Many people can become infected with the virus but not develop any illness, while those who do generally only get a runny nose or cough.
The term 'myelitis' means inflammation of the spinal cord.
Transverse myelitis is the broad name of the disease, and there are various sub-types.
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