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.
WHAT IS ENTEROVIRUS-D68?
Enterovirus-D68 (EV-D68) is a type of non-polio causing virus.
It was first identified in the US in 1962 but numbers were low. It has become increasingly common over time but is hard to keep track of because most cases aren’t recorded.
Many people infected with the virus don’t develop any illness, while those who do generally only get a runny nose or cough.
However, it can cause more serious breathing problems and scientists now believe it may be a trigger for acute flaccid myelitis, a condition which triggers swelling in the spinal column and causes paralysing nerve damage.
EV-D68 is believed to spread the same way cold and flu germs do – through the coughs and sneezes of other infected people.
Children and teenagers are the most likely to become ill because adults have usually been exposed to them without problems already, making them immune.
EV-D68 infection can only be diagnosed with specific lab tests and there is no cure for illness caused by it.
EV-D68 is believed to spread through the coughs and sneezes of people who have it, but most AFM cases are believed to have been isolated and not clustered in communities.
AFM is believed to cause paralysis by triggering swelling around the spinal cord, so putting pressure on and damaging nerves.
When these nerves are damaged it interrupts the electrical signals being sent around the body to control muscle movements.
The illness, which typically affects children, starts off with cold-like symptoms and tiredness, before the patient’s arms and legs start to go floppy.
By the time doctors realise what is wrong with the patient, the potentially irreversible nerve damage is often already done.
‘[AFM] is incredibly scary for patients and families,’ Dr Moline said.
Public Health England last year announced it had launched an investigation after the condition was found in at least 28 people in the country.
Most cases were diagnosed in the autumn of 2018 and marked a huge spike – there had only been 25 cases in the previous eight years combined.
Chloe Stevenson, a three-year-old from Plymouth, was one of the children affected by the condition.
She was left with a paralysed left arm and spent months receiving hospital treatment after being struck down with the crippling illness in September.
Her mother, Vanessa Carter, told MailOnline in January: ‘When she was first in hospital she could only wake up for five minutes at a time and became more and more weak.
Chloe Stevenson’s parents, Vanessa Carter and Ross Stevenson, noticed something was wrong with their daughter when, after complaining of being sleepy, her left arm went floppy while they were bathing her
‘We couldn’t have taken her to hospital any sooner – she just said she was tired and never complained about her arm.’
Although Chloe’s condition was improving at the time, Ms Carter said she was ‘struggling to cope’ with not understanding the illness.
She added: ‘We don’t know how much she will recover. We don’t know her long-term prognosis and I don’t know if she could get it again.’
WHAT IS ACUTE FLACCID MYELITIS (AFM)?
Acute flaccid myelitis is a form of myelitis, a term which means inflammation of the spinal cord.
Transverse myelitis is the broad name of the disease, and there are various sub-types.
It is a neurological disorder which inflames the spinal cord across its width (‘transverse’), destroying the fatty substance that protects nerve cells.
That can lead to paralysis.
AFM is an unusual sub-type of transverse myelitis.
Patients starts with the same spinal inflammation, but their symptoms are different and the disease develops differently.
The main distinction is that AFM patients are weak and limp, while patients with general transverse myelitis tend to be rigid.
Most AFM patients start to struggle with movement of the limbs, face, tongue, and eyes.
They then begin to lose control of one limb or sometimes the whole body – though many maintain control of their sensory, bowel and bladder functions.
Unlike transverse myelitis, which has been around for years, doctors are still in the dark about why and how AFM manifests itself.