Another 34 children in Britain have been struck down by hepatitis as the mysterious outbreak continues to sweep the world.
Health bumps confirmed nearly three dozen cases of liver inflammation have been detected in those aged 10 and under since Monday, bringing the total UK-wide total to 145.
Of these cases, 108 are in England, 17 are in Scotland, 11 are in Wales and nine are in Northern Ireland.
Ten youngsters have needed a liver transplant but no deaths have been reported in the UK.
It comes as experts warned the cause of the peculiar hepatitis pattern — which has been spotted in 200 children worldwide since March — won’t be known for months.
Overall, one child is confirmed to have died and another fatality in the US is currently being probed. At least 18 sickened youngsters needed a liver transplant.
None of the cases tested positive for normal hepatitis-causing viruses, which has left scientists puzzled about the origins of the disease.
Professor Alastair Sutcliffe, a leading paediatrician at University College London, told MailOnline health chiefs may not know the cause until later this summer.
A common virus which normally causes the common cold, known as adenovirus, is thought to be involved.
But there are a number of conflicting theories about why the normally harmless virus is causing critical illness in young, previously-healthy children.
More than 200 children have been sickened by the condition across the world in up to 14 countries since last October *cases in Canada, Japan and Wisconsin, Illinois and New York are still yet to be confirmed
In an update today, the UK Health Security Agency (UKHSA) said its findings continue to suggest adenovirus may be behind the sudden onset hepatitis cases.
Most of the cases have been among under-fives but ‘small number’ of children over the age of 10 are also being investigated, the UKHSA said.
The affected children initially suffered from diarrhea and nausea, followed by jaundice — yellowing of the skin and whites of eyes.
But the UKHSA said it is not typical to see this pattern of symptoms of adenovirus, so it is still probing other causes, including Covid itself.
It also noted that lockdowns may have weakened the immunity of children and left them more susceptible to the virus, or it may be a mutated version of adenovirus.
The agency is working with scientists and doctors across the country to ‘answer these questions as quickly as possible’.
Experts are also investigating whether a new variant of coronavirus is responsible or if it could be a case of a previous or concurrent Covid infection.
Dr Meera Chand, director of clinical and emerging infections at UKHSA, said parents may be concerned but the likelihood of their child developing hepatitis is ‘extremely low’.
‘However, we continue to remind parents to be alert to the signs of hepatitis – particularly jaundice, which is easiest to spot as a yellow tinge in the whites of the eyes – and contact your doctor if you are concerned,’ she said.
Dr Chand added: ‘Normal hygiene measures including thorough handwashing and making sure children wash their hands properly, help to reduce the spread of many common infections.
‘As always, children experiencing symptoms such as vomiting and diarrhea should stay at home and not return to school or nursery until 48 hours after the symptoms have stopped.’
Hepatitis is usually rare in children, but experts have already spotted more cases in the UK since January than they would normally expect in a year.
Cases are of an ‘unknown origin’ and are also severe, according to the World Health Organization.
There are 27 suspected and confirmed cases in the US, with seven announced in California yesterday. One child’s death in Wisconsin is being probed by officials.
Scientists have previously suggested cases could be just the ‘tip of the iceberg’, with more likely to be out there than have been spotted so far.
But Professor Sutcliffe said: ‘With modern methods, informatics, advanced computing, real time PCR and whole genome screening, I would think finding the cause with some reasonable reliability will take three months.’
Professor Sutcliffe said discovering the cause could be slowed by red tape across international boundaries, with difficulties in transporting biomaterials across countries.
Parental consent, data protection and laws regulating the use of human tissue in the UK could all act to slow research, he said.
Searching for an unknown cause is especially hard because cases may have multiple factors behind them that are not consistent across all illnesses.
Professor Deirdre Kelly, a pediatric hepatologist at the University of Birmingham, also told MailOnline it will take months to find a cause.
She said: ‘[These are] complex investigations, which take time.’
UK health officials have ruled out the Covid vaccine as a possible cause, with none of the ill British children having been vaccinated because of their young age.
Covid lockdowns may be behind the mysterious spate of hepatitis cases in children because they reduced social mixing and weakened their immunity, experts claim
Liver experts described the spate of cases as ‘concerning’ but said parents should not worry about the illness affecting their children.
European Center for Disease Prevention and Control (ECDC) official said the disease was ‘quite rare’ but judged the risk to children as ‘high’ because of the potential impact.
The risk for European children cannot be accurately assessed as the evidence for transmission between humans was unclear and cases in the European Union were ‘sporadic with an unclear trend’, it said.
But given the unknown causes of the disease and the potential severity of the illness caused, the ECDC said the outbreak ‘constitutes a public health event of concern’.
The surge in hepatitis cases was first recorded in Scotland on March 31, with one child in January being hospitalized with the condition.
The Scottish case was dated back to January.
At least one child has died of the mysterious disease so far, according to the World Health Organization.
Wisconsin is the only US state to report a suspected child death from hepatitis. If confirmed, it will be the second in the world.
State officials confirmed to the DailyMail.com that the child had developed the disease after being infected with the adenovirus.
Most of the infected children were under 10 and many were under the age of five. None had other underlying health conditions.
The agency recommended improving surveillance and hygiene practices to stop the spread of cases.
Q&A: What is the mysterious global hepatitis outbreak and what is behind it?
What is hepatitis?
Hepatitis is inflammation of the liver that is usually caused by a viral infection or liver damage from drinking alcohol.
Some cases resolve themselves, with no ongoing issues, but a fraction can be deadly, forcing patients to need liver transplants to survive.
Why are experts concerned?
Hepatitis is usually rare in children, but experts have already spotted more cases in the current outbreak than they would normally expect in a year.
Cases are of an ‘unknown origin’ and are also severe, according to the World Health Organization. It has caused up to two deaths and 18 liver transplants.
How widespread are cases?
The inflammatory liver condition has been spotted in more than 200 children aged between one month and 16 years old.
Fewer than five
*cases in Canada, Japan, and Illinois, Wisconsin and New York are still yet to be confirmed
What might be triggering it?
None of the cases have been caused by any of the five typical strains of the virus — hepatitis A, B, C, D and E — leaving experts baffled by the outbreak.
Some children have tested positive for adenovirus, which usually causes cold, while others have been infected with Covid — but no clear theme has emerged.
The UKHSA ruled out the Covid vaccine as a possible cause, with none of the British cases so far having been vaccinated because of their age.
What are the top theories?
Experts say the cases may be linked to adenovirus, commonly associated with colds, but further research is ongoing.
This, in combination with Covid infections, could be causing the spike in cases.
The WHO reported adenovirus has been detected in at least 74 of the cases. At least 20 of the children tested positive for the coronavirus.
British experts tasked with investigating the spate of illnesses believe the endless cycle of lockdowns may have played a contributing role.
Restrictions may have weakened children’s immunity because of reduced social mixing, leaving them at heightened risk of adenovirus.
This means even ‘normal’ adenovirus could be causing the severe outcomes, because children are not responding to it how they did in the past.
Other scientists said it may have been the adenovirus that has acquired ‘unusual mutations’.
This would mean it could be more transmissible or better able to get around children’s natural immunity.
New Covid varying
UKHSA officials included ‘a new variant of SARS-CoV-2’ in their working hypotheses.
Covid has caused liver inflammation in very rare cases during the pandemic, although these have been across all ages rather than isolated in children.
The UKHSA has noted environmental triggers are still being probed as possible causes of the illnesses.
These could include pollution or exposure to particular drugs or toxins.
What are the symptoms?
Hepatitis often has no noticeable symptoms — but they can include dark urine, pale grey-coloured faeces, itchy skin and the yellowing of the eyes and skin.
Infected people can also suffer muscle and joint pain, a high temperature, feeling and being sick and being unusually tired all of the time.
How is it treated?
Treatment depends on severity, with some patients able to fight off the illness on their own.
In more dangerous cases where the liver fails, children can be put into induced comas to deal with brain swelling caused by ammonia build-up.
A liver transplant may be necessary if the liver has become damaged to self-repair, although this is incredibly rare.