Around 190 unexplained cases of severe hepatitis have been reported in children around the world as scientists urgently investigate what is causing the outbreak.
The first case was reported in Britain this month where 111 children, mostly under the age of 10, have been found to have the illness.
Hepatitis is the term used to describe inflammation of the liver and is usually the result of a viral infection.
Severe hepatitis is rare in otherwise healthy children.
However, the outbreak now includes at least 12 countries and has reached Asia after a case was identified in Japan on 21 April.
The child had tested negative for adenovirus, a possible cause being investigated worldwide, and COVID-19.
Canada’s Public Health Agency said on Tuesday it was also investigating reports of severe hepatitis in young children.
It did not reveal the number of potential cases or where they were reported.
Meanwhile, cases of severe hepatitis of unknown origin have been confirmed in the US and Israel.
The European Centre for Disease Prevention and Control (ECDC) has said around 190 unexplained cases of severe hepatitis have been reported in children around the world, with some 40 cases recorded in the European Union and the European Economic Area.
The ECDC is investigating alongside national authorities and the World Health Organisation (WHO).
Read more: The girl who had just hours to live, as rare hepatitis cases rise in children
Unusually, the new cases do not feature the viruses typically responsible for acute liver inflammation – hepatitis A, B, C, D and E.
According to the WHO, 17 children have needed liver transplants as a result of the recent cases, and one has died.
ECDC director Andrea Ammon said the investigations so far pointed towards a link to infection with an adenovirus, a family of common viruses that can cause flu-like or gastrointestinal symptoms.
What is driving the surge in sudden onset hepatitis in young children?
Ms Ammon said a theory that COVID-19 lockdowns may have weakened children’s immunity, because they were less exposed to common pathogens while in isolation, was one of several being considered.
Scientists are also investigating whether the adenovirus involved has mutated, or is acting in tandem with another
infection, possibly COVID-19. A toxin could also be responsible, but this is thought less likely due to the geographical spread of the cases reported.
Any link with COVID-19 vaccination has been ruled out.