Children have been diagnosed with the inflammatory liver condition in at least seven countries, including the UK, where 74 cases are under investigation.
Those receiving treatment have been screened for common viruses that cause hepatitis but none have been detected. Health officials are investigating “possible links” to other pathogens, such as adenovirus and coronavirus.
The 12 cases in Israel were discovered after its health ministry asked hospitals and clinics to report any cases of liver disease in children following reports of hepatitis in the UK and elsewhere.
Five cases were reported from the Shaare Zedek Medical Center, in Jerusalem, and seven were identified at the Schneider Children’s Medical Center, in Petah Tikva.
Health officials from the Schneider Children’s Medical Center said cases there had all previously been infected with Covid-19.
Additional cases of hepatitis have been identified in Denmark, Ireland, the Netherlands and Spain, the European Centre for Disease Prevention and Control said in a statement Tuesday. It did not specify how many cases were found.
Nine cases have also been detected in children aged 1 to 6 in Alabama, in the US.
Last week, the World Health Organisation (WHO) warned it was likely that more cases of hepatitis among young children in the UK were likely to be reported in the coming days.
In an update on Friday, the WHO said it was notified on 5 April of 10 cases of severe acute hepatitis in children under the age of 10. By 8 April, 74 cases had been identified in the UK.
“Given the increase in cases reported over the past one month and enhanced case search activities, more cases are likely to be reported in the coming days,” a spokesperson warned.
Of the 10 cases reported by 5 April, nine had started to fall ill in January. Symptoms included jaundice, diarrhoea, vomiting and abdominal pain. All 10 were detected after hospitalisation, the WHO said.
Of the total 74 cases, some children needed to be transferred to specialist liver units, while six have had liver transplants.
The WHO said coronavirus and adenovirus have been detected in several cases. “Though the role of these viruses in the pathogenesis (mechanism by which disease develops) is not yet clear,” it said.
Adenoviruses are a family of common viruses that usually cause a range of mild illnesses and most people recover without complications. They can cause a range of symptoms, including colds, vomiting and diarrhoea. While they don’t typically cause hepatitis, it is a known rare complication of the virus.
“No other epidemiological risk factors have been identified to date, including recent international travel,” the WHO added in Friday’s statement. “Overall, the aetiology [cause] of the current hepatitis cases is still considered unknown and remains under active investigation.”