Experts investigating sudden onset hepatitis cases in children have ruled out a link with dogs, a leading professor said.
Calum Semple, professor of child health and outbreak medicine at the University of Liverpool, told a briefing that investigations had found no role for either owning dogs or recent contact with dogs in cases of acute hepatitis.
The UK Health Security Agency (UKHSA) noted previously that around 70% of a sample of affected children had had recent contact with dogs or owned dogs.
As of May 10, 176 people have experienced sudden onset hepatitis in the UK, of which 128 are in England, 26 in Scotland, 13 in Wales and nine in Northern Ireland.
Most cases are in children under the age 0f 10, though some teenagers have also been recently identified with the the illness.
Many of those affected have experienced vomiting and diarrhoea, and cases have been reported worldwide, with the US saying on Wednesday it was investigating 180 cases.
Prof Semple said the UKHSA was now due to announce “there’s nothing to indicate the role of dogs in children with acute hepatitis”.
He added that the hypothesis “has now been removed from the line of investigation by the public health agencies in England and in Scotland”.
Experts attending the briefing said no clear cause of the hepatitis cases had yet been established.
Prof Semple said there was currently a stronger association with adenovirus (a common illness which can cause cold or flu-like symptoms) than with Covid-19.
He said Covid was moving down the list of possible reasons, though other experts said it may still play a role indirectly and was still being looked at.
One type of adenovirus – type 41 – is being looked at closely as it typically presents as diarrhoea, vomiting and fever.
Professor Will Irving, an expert in hepatitis from the University of Nottingham, said it may be difficult to come to any conclusions about the role of Covid because the background levels of Covid in the population have been so high that “statistically one would need very large numbers of cases to prove a statistically significant difference between them and background population”.
Experts are also looking at whether hepatitis may be caused by a common infection, with some children having a genetic predisposition which is leading to severe disease.
Deirdre Kelly, professor of paediatric hepatology at the University of Birmingham, said it was “highly unusual” to have so many cases of serious liver disease in children, with the UK usually seeing about 20 cases a year of youngsters needing specialist care.
She said it was hard to know whether adenovirus may be a cause or trigger.
She said: “Around 70% of the children do have low levels of adenovirus in their blood… it’s very difficult to know whether this is the cause… or whether this was a trigger in the child who was susceptible for some other reason.”
Prof Irving added: “The adenovirus is the leading contender here, but we do need more data to be convinced, at least I do, that the adenovirus is a primary cause.
“I would also say I strongly suspect this will turn out to be multifactorial, there won’t be a single factor here that explains this phenomenon.
“It will be a coalescence of two or three or four aspects that is leading to this increased number of cases.”
Dr Tassos Grammatikopoulos, from King’s College Hospital NHS Trust, said data suggested that the peak of cases of hepatitis in children had now passed.
He said that “although we do still get some cases being identified in the UK, we seem to be on a downward trend”.