When Yolanda Brunson's family tested positive for COVID-19 last year, she was relieved her four-year-old son, DJ, showed no symptoms.
But weeks later, her usually happy, energetic little boy was in hospital.
Ms Brunson was terrified.
"It was one of the most gut-wrenching, heart-wrenching experiences that I've ever had," she told the ABC in the US state of Maryland.
"It was really, really, really hard."
When DJ first started feeling unwell, he had a temperature and some stomach pain.
Doctors told Ms Brunson it was probably unrelated to his coronavirus infection — perhaps a bug he had picked up at pre-school.
The fevers continued to come and go, though, along with periods of lethargy.
When his temperature spiked again, his parents took him to hospital, where he ended up being admitted for more than a week.
"I know for me personally, it just makes you feel hopeless because you're sitting there and he's crying," DJ's father, Daryl Brunson, said.
"You're talking about a four-year-old kid who wants to run around and play. That's all he wanted to do, was just get up and get out of bed."
DJ was diagnosed with a rare post-COVID condition called multi-system inflammatory syndrome in children, or MIS-C.
In Australia, it is sometimes referred to as paediatric inflammatory multisystem syndrome, or PIMS-TS.
Paul Offit, a doctor at the Children's Hospital of Philadelphia, said it was most common in children around the age of nine, weeks after they had experienced a mild or asymptomatic case of COVID-19.
"They're no longer positive, they're no longer shedding infectious virus," he said.
"It can be quite severe, it can require an intensive care unit admission and it can be fatal."
While the complication is still extremely rare, the highly infectious Omicron variant is pushing infections in the US to record numbers.
As cases have surged, so too have hospital admissions of children infected with COVID-19.
Experts are not yet sure whether a rise in MIS-C cases could soon follow the peak.
The mysterious COVID complication
More than 6,000 cases of MIS-C have been diagnosed in the United States among children who have contracted COVID-19 or been exposed to someone carrying the virus.
Fifty-five American children have died.
In Australia, there have been no deaths out of 35 cases reported by a network of children's hospitals known as paediatric active enhanced disease surveillance (PAEDS).
No-one quite understands why COVID-19 can trigger MIS-C.
But some scientists believe a child's body can have a delayed reaction to the virus, with the immune system going into overdrive and causing inflammation in the organs.
The good news is that two years into the pandemic, doctors are better at recognising and treating the disease.
"We are getting much better now at recognising the syndrome and treating it," Nigel Crawford from the Murdoch Children's Research Institute in Melbourne said.
"We've worked hard with our colleagues around Australia to recognise some of the symptoms and institute early treatment, which means we've had some good outcomes with managing this condition."
Dr Offit said the emergence of MIS-C initially took the medical community by surprise and he believed there needed to be more awareness of the condition.
"If your child has an infection and recovered from that infection, then a month later has symptoms of high fever, difficulty breathing, I think they should immediately bring them to the doctor and we should see whether or not this is MIS-C," he said.
"There are now better therapies to treat MIS-C, whether it's steroids or other anti-inflammatories or plasmapheresis (cleaning the blood), there are definitely therapies that are being brought forward that do seem to hasten resolution of the illness."
Vaccines may help ward off MIS-C
DJ has since recovered from MIS-C and he was recently given the all clear by his cardiologist for an ongoing heart issue associated with the condition.
"He's back, 100, 120 per cent and is going strong. The future is bright," Mr Brunson said.
At four, DJ is too young to be vaccinated, but experts say there is a simple step that parents of children over five can take to reduce the risk of MIS-C.
Two doses of Pfizer's vaccine reduce the risk of MIS-C in adolescents between the ages of 12 to 18 by 91 per cent, according to a recent report published by the US Centres for Disease Control (CDC).
The data was gathered between July and December last year, when the Delta variant was still dominant in the US.
While vaccines have only recently become available to children between the ages of five and 11 in Australia, they have been on offer to Americans in that age group since November.
Using information from the CDC, the American Academy of Paediatrics estimates 27 per cent of children aged five to 11 have received at least one dose of a vaccine so far.
"When [unvaccinated children] come in with this preventable illness, it's especially hard, and it's very difficult for [parents] to watch their child struggle," Dr Offit said.
The Omicron wave and children
For the week ending January 8, the CDC reported that more than seven in 100,000 American children aged four and under were in hospital with COVID-19 – more than twice the rate reported a month ago.
In comparison, the rate of five to 11-year-olds in hospital with COVID-19 was 1.3 per 100,000.
While Omicron is still being studied, it appears the new variant does not affect young children with particular severity.
"We have not yet seen a signal that there is any increased severity in this age demographic," Rochelle Walensky, the CDC's director, said earlier this month.
Dr Walensky also acknowledged some children were coming to hospital for other reasons and being diagnosed with COVID-19 through routine screening.
The estimated 19 million American children under five may be in a long wait to be eligible for vaccination.
A trial by Pfizer for kids between two and five in December did not yield promising results, though the study continues.
With MIS-C appearing two to six weeks after a COVID-19 infection, it will be some time before the US learns whether the surge in Omicron cases also leads to a surge in complications among children.
Yolanda and Daryl Brunson want their family's experience to help educate others on what to look out for if their child comes down with COVID-19.
"I really do not want any parent to go through what my husband and I went through, it was traumatic," Ms Brunson said.
"But just in case, if you're in that percentage, make sure that you do your due diligence and your research and you advocate for your child and you engage with that team of doctors."
