Doctors believe an unusual outbreak of acute hepatitis among children may have peaked in the UK, as work continues to understand the cause of the mysterious illness.
Figures released on Friday by the UK Health Security Agency show that 197 children have been diagnosed with unexplained acute hepatitis this year, with 11 becoming so ill they needed a liver transplant. None in the UK have died.
The health agency launched an investigation in April after hospitals reported a rise in cases of acute childhood hepatitis with no known cause. Typically, UK hospitals see about 20 cases a year that are not caused by common hepatitis viruses, but cases this year are nearly 10 times higher.
The latest report from the UKHSA shows that while new cases are still coming to light, the rate appears to have slowed. “Potential reporting lags mean that the rate of new cases is uncertain, though the current rate is more consistent with plateauing than exponential growth,” it states.
Scientists studying the outbreak suspect that adenovirus, a common infection that can cause colds, vomiting and diarrhoea, may be involved in the outbreak, but the virus does not normally cause hepatitis in otherwise healthy children.
Tests on the sick children showed that 68% were positive for adenovirus, mostly in the blood. But levels of adenovirus and other respiratory viruses soared to unusually high levels in the spring as Covid restrictions eased, meaning infections were widespread in the general population.
DNA studies are now under way to see whether the affected children have a genetic susceptibility to hepatitis, or whether the type of adenovirus identified in most children, known as adenovirus 41F, has mutated into a form that can trigger the disease in some children. One possibility is that an infection might provoke an abnormal immune response in some children, which attacks the liver tissue.
“This could well be a very, very common infection by one virus, or more viruses, and the vast majority of us don’t even know we’ve had it, but there might be a genetic predisposition that means some children go on to get severe disease,” said Calum Semple, professor in child health and outbreak medicine at the University of Liverpool.
Tests on liver tissue from children who had transplants have not revealed a direct cause of the damage. Prof Semple said there is nothing to suggest that coronavirus, detected in 15% of cases, is directly involved, though an indirect effect has not been ruled out. There is no link to coronavirus vaccines. The majority of cases are in children under five years old, who are too young to receive the jab.
Will Irving, a professor of virology at the University of Nottingham, said the involvement of adenovirus is the “leading contender” but that many factors might be contributing to the wave of cases. The spring rise in cases may simply be more of what hospitals saw before, he added, with the increase driven by high levels of virus in the community.
Although the UKHSA is still searching for the cause, the agency has ruled out a link with pet dogs. Questionnaires filled out by affected families found that about 70% of the children had contact with dogs, but “extended investigations” found nothing to suggest a problem. “There’s nothing to indicate a role of dogs with children with acute hepatitis,” said Prof Semple. “We can put that one to bed now.”
Dr Tassos Grammatikopoulos, a consultant in paediatric hepatology and honorary senior lecturer at King’s College hospital, said there were still cases coming through, but the UK seemed to be on a downwards trend. “We seem to be past the peak,” he added.