THE number of children in Scotland struck down by an unexplained liver disease outbreak has climbed to 32, amid warnings from the World Health Organisation that the mystery "has to be taken seriously".

Doctors at Glasgow's Royal Hospital for Children were the first in the world to alert health authorities to the issue at the end of March this year, following a string of admissions among three to five-year-olds suffering from acute hepatitis - inflammation of the liver - where the cause was unknown.

As of June 6, a total of 704 cases have been reported in 34 countries worldwide.

At least 38 children have required liver transplants, and 10 have died.

In the UK, a total of 240 cases have now been identified including 32 in Scotland - an increase of one since Public Health Scotland's last update on May 27.

The majority of cases are in children under five, with no deaths in the UK.

READ MORE: What's really behind the mystery hepatitis outbreak sickening young children?

It comes as Dr Philippa Easterbrook, a technical lead for the World Health Organisation, addressed the outbreak at the World Hepatitis Summit.

Dr Eastbrook said: "In terms of how worried we should be about this outbreak, it’s the first time so many cases of severe acute hepatitis have been seen.

“A proportion of cases have developed liver failure, required transplantation or resulted in death. It has to be taken seriously.

"An important step at the moment is to understand its cause.”

Investigations are ongoing, but one of the leading theories is that the liver inflammation may have been triggered by an overzealous immune response to infections caused by adenovirus.

The vast majority of cases worldwide are in children under five.

It is thought that a lack of exposure to adenovirus - which commonly causes cold-like or gastrointestinal symptoms - over the past two years as a result of social distancing and pandemic lockdowns may have disrupted young children's immune responses.

In the UK, adenovirus has been the most commonly detected pathogen among the affected patients, being picked up in around two thirds of test samples.

In contrast, SARS-CoV2 - the virus behind Covid - was found in just 15% of children tested, although a link to Covid has not been ruled out.

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Dr Eastbrook confirmed that much of the data so far has been gathered from the UK and USA where hepatitis cases are highest - including some traced retrospectively to October 2021.

The common viruses typically associated with acute viral hepatitis (hepatitis viruses A, B, C, and E) have not been detected in any of the known cases worldwide, she said.

Dr Easterbrook also confirmed that common bacterial infections have not been detected and there is no clear link to a particular geographic area, or common exposure to specific foods, medications, toxins, animals or to travel.

She added that there is no link to the Covid-19 vaccine as the majority of children (85%) were unvaccinated.

READ MORE: Covid infections across UK rising for first time since March

Dr Renu Bindra, senior medical advisor and incident director at the UK Health Security Agency, said: "Our investigations continue to suggest an association with adenovirus, and we are exploring this link, along with other possible contributing factors including prior infections such as Covid-19.

"We are working with other countries who are also seeing new cases to share information and learn more about these infections.

"The likelihood of children developing hepatitis remains extremely low. Maintaining normal hygiene measures, including making sure children regularly wash their hands properly, helps to reduce the spread of many common infections, including adenovirus.

"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."