A child in Ireland has died after contracting acute hepatitis, the Irish Health Service Executive (HSE) confirmed.
The tragic news comes as the World Health Organization (WHO) said on Tuesday that global children's hepatitis cases have risen to 348.
UK Health Security Agency (UKHSA) investigators have noted the "relatively high numbers of dog-owning families" and the significance of this finding is being "explored", the Mirror reported.
There are 163 UK cases as of May 3 according to the UKHSA'S most recent update. Of these children, 11 have received a liver transplant and none have died.
The most probable cause for the mystery illnesses is a strain of adenovirus called F41, says the UKHSA, which has also found no evidence of any link to the Covid vaccine.
The majority of cases are in kids under five who are too young to have received the vaccine.
Meanwhile, reports have suggested pet dogs may be behind the new cases.
"Relatively high numbers of dog-owning families" were among those affected by the hepatitis outbreak, according to a questionnaire of families.
However, the UKHSA said: "The significance of this finding is being explored," but added "pet dog ownership is common in the UK".
Dr Meera Chand, director of clinical and emerging infections at UKHSA, said: "It's important that parents know the likelihood of their child developing hepatitis is extremely low.
"However, we continue to remind everyone to be alert to the signs of hepatitis – particularly jaundice, look for a yellow tinge in the whites of the eyes – and contact your doctor if you are concerned.
"Our investigations continue to suggest that there is an association with adenovirus and our studies are now testing this association rigorously."
Since March, the HSE said that there have been six probable cases of children with hepatitis in the country. It said this "is more than would usually be expected over this period of time".
All children were aged between one and 12 years of age, and all had been hospitalised.
The children affected have no links to the other children involved, and no single virus has yet been identified.
The Irish cases have no links to the UK cases, the HSE said, and none had a recent travel history to the UK.
The common viruses that cause hepatitis: hepatitis viruses A, B, C and E; have not been detected in any of the cases reported worldwide.
Authorities are investigating links between this form of hepatitis and an increase in infections caused by adenovirus, a common cause of childhood illness, as well as other infections including Covid-19.
Irish authorities are liaising closely with the ECDC (European Centre for Disease Prevention and Control), the World Health Organisation and authorities in the UK to identify the cause of the illness.
The sudden rise of hepatitis cases in children is prompting health bosses to remind parents to stay alert for symptoms as the outbreak grows.
No children have died so far in the UK, but worryingly, 13 children are in hospital and 11 have needed a liver transplant, while 88 have been discharged and made a full recovery.
According to UK health chiefs, vomiting and jaundice are the most common symptoms experienced by children in hospital with liver inflammation.
According to WHO, one death of hepatitis has been confirmed with five reported by the US and three by Indonesia.
However, infection by the usual hepatitis types A-E has been ruled out as a potential cause.
Although a common virus called adenovirus is being closely looked at as this can cause sore throats, ear infections and stomach bugs.
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