According to the World Health Organization (WHO), dozens of cases of acute hepatitis of unclear origin have occurred in children in Great Britain.
The hepatitis viruses A, B, C, E and D were excluded after laboratory tests, the WHO reported on Friday in Geneva.
In several cases, a corona infection or adenoviruses or both were detected in the small patients.
It is not yet clear whether this is the trigger.
The WHO called on all countries to be vigilant to detect possible cases.
Three other cases were reported from Spain, including a 13-year-old child.
A few suspected cases had been reported from Ireland, not all of which had been confirmed.
The cases would be investigated extensively, for example to determine whether the minors had previously traveled to certain countries or been exposed to possible poisoning.
Ten cases of acute hepatitis in previously healthy children between the ages of eleven months and five years were reported from Scotland on April 5, the WHO reported.
One of the children had the first symptoms in January, the others in March.
Symptoms are gastrointestinal problems or jaundice.
The acute hepatitis with greatly increased liver enzymes was discovered upon admission to the hospital.
Just three days later, on April 8, there were already 74 cases in Great Britain, all in children under the age of ten.
Six children would have needed liver transplants.