The UK Health Security Agency (UKHSA) has reported a further 34 cases of mysterious liver damage in children, and found hints of a possible cause.

Over the last few months, an unusual rise in liver damage in children has been seen in the UK, US, and Europe, prompting the World Health Organization (WHO) to closely monitor the situation. On April 5, the WHO was informed of 10 cases of severe acute hepatitis (inflammation of the liver) in children under the age of 10 in Scotland.

Three days later, it had received reports of 74 cases across the UK. Usually in Scotland, there are around 7-8 cases in a year in patients without underlying conditions. Similar cases have been reported in Alabama, with a few cases also being reported in Ireland and Spain. Today's announcement brings the total number of cases to 108 in the UK.

Though it's by no means confirmed as of yet, UKHSA said that there continued to be evidence pointing towards a link to adenovirus infection, as 77 percent of cases tested were positive for adenovirus.

"We are working with the NHS and public health colleagues in Scotland, Wales and Northern Ireland to swiftly investigate a wide range of possible factors which may be causing children to be admitted to hospital with liver inflammation known as hepatitis," Dr Meera Chand, Director of Clinical and Emerging Infections at UKHSA, said in a statement.

"Information gathered through our investigations increasingly suggests that this is linked to adenovirus infection. However, we are thoroughly investigating other potential causes."

The body is also looking at any potential changes to the adenovirus genome, and investigating possible contributing factors such as COVID-19. 

In a case report based on the patients first seen in Scotland, doctors note that the severity of the disease seen in the children was "unfortunately remarkable". They report that the children had no significant medical history prior to their admission to hospital, where all of them stayed for at least six days, with three children requiring a liver transplant. Symptoms in the cases were similar.

"For two children close contact in a household or other setting with two other cases was reported. Symptoms reported include jaundice (eight of nine cases), abdominal pain (seven of nine cases), and nausea and malaise (six of nine cases) leading up to admission," the report, published in Eurosurveillance, notes. "Nearly all of them reported gastrointestinal symptoms including diarrhoea or vomiting and lethargy, but not fever, in the weeks before admission."

Though concerning, experts highlight the fact that the liver is very good at regenerating itself over time. Parents and carers should get in contact with a healthcare provider should they notice any symptoms of hepatitis in their children. In the meantime, health authorities and the WHO will continue to investigate.