A toddler had to have a liver transplant after being struck down by the mysterious wave of hepatitis that has infected at least 110 American children and killed five.

Baelyn Schwab is pictured in hospital while awaiting a liver transplant last month after the two year-old became one of around 110 American children to come down with hepatitis.

That prompted them to schedule a liver transplant for Baelyn just two weeks after she first fell ill. .

M Health Fairview says it normally performs about 10 liver transplants on children in an average year, but has performed two transplants on children suffering from liver failure this year so-far.  .

Baelyn Schwab received a liver transplant on May 5 - just two weeks after the two year-old from South Dakota fell ill with hepatitis as the disease infects scores of American children .

She was found to have tested positive for the adenovirus, a condition which some scientists believe may be linked to the outbreak.

EXCLUSIVE: Mysterious hepatitis outbreak in children will continue 'throughout the summer' and many cases remain undiagnosed, expert warns - as global death toll rises to 12 including five deaths in America.

America's outbreak of mysterious hepatitis will continue 'throughout the summer' and many cases are already undiagnosed, a top virologist warned Friday — as the global death toll hit 12 with five fatalities in the United States.

Dr Binnicker also warned many hepatitis cases among children remain undiagnosed in the U.S.

because, in some cases, children will not have been unwell enough for their parents to take them to a doctor or hospital.

The majority of children with the mysterious hepatitis in the U.S.

At least 12 children have now died from the mysterious hepatitis worldwide, with five fatalities also reported in Indonesia and one each in Ireland and Palestine.

More than 110 cases across 26 states have been registered so far, with 15 children becoming so severely ill they needed a liver transplant.

Dr Matthew Binnicker, a clinical virologist at the Mayo Clinic, warned cases would continue to crop up this year.

Speaking exclusively to DailyMail.com, Dr Binnicker said: 'I would not be comfortable saying this outbreak has peaked.

'I'd say cases will continue to emerge throughout the summer period because we will continue to see children in day care where there is higher transmission.

'This type of adenovirus we don't tend to think of as seasonal, we will continue to see cases throughout the year.'.

The adenovirus most children with mysterious hepatitis have tested positive for is scientifically termed type 41.

Some cases resolve themselves, with no ongoing issues, but a fraction can be deadly, forcing patients to need liver transplants to survive.

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.

Experts say the cases may be linked to adenovirus, commonly associated with colds, but further research is ongoing.

Around three-quarters of British cases have tested positive for the virus. .

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'

Covid has caused liver inflammation in very rare cases during the pandemic, although these have been across all ages rather than isolated in children. 

He said that with about 90 percent of children who went to see a physician being hospitalized it would mean there is just a 'small percentage' who were not sick enough to go to the doctors

He said hepatitis cases that have not been diagnosed but have got better on their own should not worry parents, as they will be unlikely to have any long-term effects

But at present he said the offer had not been taken up, likely because there was only a relatively small number of cases to date

It is not clear how many of these were already included in the CDC's count of mysterious hepatitis cases

He said scientists were still probing cases to establish a cause but that adenoviruses were 'top of the list'

There have been around 350 cases of 'severe hepatitis of unknown origin' in children recorded in 21 countries since April

In new guidance this week, the CDC in the US has told doctors treating children with hepatitis to take liver samples for analysis