A British mother described her family's "very, very scary" experience after her three-year-old son developed a rare illness that has been linked to COVID-19.

In recent weeks, several European countries have reported cases of young patients appearing with unusual symptoms similar to those of Kawasaki disease – a rare illness found in children – that include a very high fever, vomiting, a rash and inflammation.

The symptoms of Hayley Grix's child, Marley, were so bad that he was hospitalized. He is now recovering, but amid the coronavirus pandemic, she is thankful things are returning to normal and the "horrific ordeal" is now over. 

Read more: Doctors told to look out for rare 'Kawasaki' symptoms in children amid possible COVID-19 link

On Easter Monday, Marley appeared to be fine, but within 24 hours he started showing mild symptoms of an illness that British officials are now looking into for links between cases and COVID-19.

"Normally, he's a very well, happy, bouncy child," said Hayley Grix, from her home in Surrey, England.

"But Easter Monday going into Tuesday, that night he was really unsettled. He was up and down all night."

She added: "Then, when I took his temperature, I realized it was 38 degrees and I thought that's a bit strange." 

His mother gave him medicine for young children to try to reduce his temperature, but he didn't respond and the symptoms worsened:

"He became lethargic. He kept moaning that his neck hurt and I couldn't see anything obvious, but come later on in the week I noticed a lump half the size of a golf ball on the side of his neck and his hands suddenly became red and inflamed, his feet and his tongue became very red and inflamed, too, as well as having bloodshot eyes.

"It was very, very scary indeed."

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Recovery

On 17 April, she took her son to hospital. At first, Marley's doctors didn't know what was wrong with him, but they came to the conclusion that his symptoms were similar to those of Kawasaki disease.   

"I'd never heard of it," says Hayley. "I speak to a lot of people and before this happened I haven't met anybody who had heard of it, so it was a real shock to us."

Marley is doing much better now, but the disease has left its mark.

"The heart scans that he had just shortly after coming out of hospital show that he's got a dilated left artery and also dilated right artery," says Hayley, but his doctors are hopeful that they will return back to normal size over several months.

The three-year-old is still taking steroids and aspirin, but according to Hayley, "he's getting his strength back, his legs are getting stronger and we're getting our bouncy little boy back."

Rare illness amid a pandemic

Both Hayley and her son were tested for COVID-19 at hospital and were placed in quarantine, but both of their tests came back negative. They were tested again 10 days later, but were again negative. 

According to Damien Bonnet, one of France's leading children's doctors and head of pediatric cardiology at Paris Descartes University, there has been a sharp increase in reported cases of illnesses similar to Marley's in the Paris area in the past three weeks.

The UK government's chief medical adviser, Chris Whitty, said the UK was looking for links between the coronavirus and the rare illness. 

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Hayley and her family are happy to put the ordeal for the most part behind them, but her experience of being at hospital during the pandemic raised serious concerns about children's healthcare in the time of coronavirus.

"When we went into the pediatrics assessment unit, Marley's name was the only child on the board and that's quite alarming, given that it would usually be wall-to-wall," said Hayley.

"What's worrying me is that parents aren't taking their children to hospital when they're actually really sick because children don't stop getting sick just because there's something else out there at the moment," she added.

"It's a bit scary that parents are potentially keeping their kids at home when they're really unwell."

Check out The Pandemic Playbook, CGTN Europe's major investigation into the lessons learnt from COVID-19.