The World Health Organisation (WHO) has recently identified around 348 probable cases of hepatitis of unknown origin.
Adenovirus is believed to be a possible cause and has been hypothesised to be a driving factor in illnesses among children.
Adenoviruses are a group of viruses that can cause infections with many different types meaning an infection can occur more than once.
According to the UK Health Security Agency, adenovirus was the most common pathogen found in 40 of 53 confirmed cases tested in the UK.
The agency said that “investigations increasingly suggest that the rise in severe cases of hepatitis may be linked to adenovirus infection, but other causes are still being actively investigated”.
"Over the last week, there's been some important progress with the further investigations and some refinements of the working hypotheses," Philippa Easterbrook, from the WHO's global hepatitis programme, told a press conference.
Is hepatitis dangerous?
In most children and adults with a healthy immune system, adenoviruses pose no major health risks with a slight illness which passes in a week or two.
Viral hepatitis from infection by adenoviruses has only been reported previously as a rare complication.
Because of the number of cases recently reported and the severity of the disease in children, scientists are urgently investigating the cause of the outbreak.
Easterbrook added that the UK has been coordinating a number of comprehensive set of studies looking at the genetics of children affected, their immune response, viruses and further epidemiological studies.
This comes as more than 160 cases of hepatitis in the UK have been reported.
The scientist said that within the week, there should be data from Britain on a case control study comparing whether the detection rate of adenovirus differs from that in other hospitalised children.
"That will really help hone down whether adeno is just an incidental infection that's been detected, or there is a causal or likely causal link," Easterbrook said.
Most hepatitis cases are known to affect those who are five years old or younger.
What are the symptoms of hepatitis?
Symptoms of hepatitis have included gastroenteritis illness such as diarrhoea, vomiting and nausea.
Jaundice which includes yellowing of the skin and eyes is another commonly reported symptom.
Dr Meera Chand, director of clinical and emerging infections at UKHSA, said: "Information gathered through our investigations increasingly suggests that this rise in sudden onset hepatitis in children is linked to adenovirus infection.
"However, we are thoroughly investigating other potential causes."
According to Kids Health, symptoms of adenoviruses can include:
- Eye redness and pain
- Diarrhoea
- Vomiting
- Belly pain
- Frequent peeing, burning pain while peeing, blood in the urine
- Headache
