Global health authorities are investigating unexplained severe hepatitis cases in children that have been recorded in more than a dozen countries worldwide.
About 190 cases of severe liver inflammation of unknown origin had been identified around the world, the European Center for Disease Prevention and Control said on Tuesday.
British health officials first sounded the alarm about the mysterious illness, which has largely affected children aged under 10 years old, in early April.
Andrea Ammon, ECDC director, said investigations about what lay behind the outbreak were “ongoing” but “the exact cause of this hepatitis still remains unknown”.
She said early findings “point towards a link to adenovirus infection”. Adenovirus — a group of viruses typically associated with symptoms, such as a persistent cough, conjunctivitis or diarrhoea — rarely leads to hepatitis in healthy children.
One possible factor, said Ammon, was that children having “little exposure” to adenovirus as a result of decreased social mixing because of Covid-19 restrictions was contributing to more severe outcomes. However, she cautioned that in terms of explaining why the cases were emerging now: “it’s all speculation”.
Three-quarters of the British children who were tested for adenovirus after falling ill with the unexplained hepatitis returned positive results, according to data from the UK Health Security Agency published on Monday. The UK had recorded 111 cases of the illness, as of April 21. The US, Israel and 10 other European nations have also recorded cases.
Tedros Adhanom Ghebreyesus, the World Health Organization’s director-general, told a news conference that 17 children had required liver transplants and one had child died after contracting the illness.
He said symptoms included abdominal pain, diarrhea, vomiting, jaundice, severe acute hepatitis, and increased levels of liver enzymes. However, the viruses that commonly caused acute viral hepatitis had not been detected in any of the cases.
Adenovirus had been detected in at least 74 cases and this, and other hypotheses, were being explored, Tedros said.
The WHO was “working closely with the European Center for Disease Prevention and Control and the affected countries to support ongoing investigations, including additional lab testing”, he added.
Scientists are also investigating whether adenovirus combined with previous coronavirus infection or simultaneous Covid-19 infection could be behind the increase in severe hepatitis.
Genomic sequencing analysis is under way to determine whether the adenovirus type 41, which has been linked to the outbreak, has taken on mutations which could lead to hepatitis.
But health officials have ruled out the possibility that traditional types of hepatitis viruses — A to E — are the cause of the outbreak, or that Covid-19 vaccination is to blame.
Phillippa Easterbrook, a medical expert in the WHO’s HIV, hepatitis and sexually transmitted infection programme, added that it was “very unusual for an adenovirus to cause this type of severe symptoms”.
She said reports of unexplained hepatitis in children occurred every year and it was possible that increased testing and awareness might be “flushing out and recognizing more cases that have always existed”.