Japan has reported its first probable case of acute hepatitis (liver damage) in a child, following a surge in cases across the US and Europe, predominantly in children under the age of 10.
In a recent update on the outbreak, the World Health Organization (WHO) announced it has been informed of 169 cases of liver damage in children aged one month to 16 years, with at least one death reported. Cases have now been found in the UK (114), Spain (13), Israel (12), the USA (9), Denmark (6), Ireland (<5), The Netherlands (4), Italy (4), Norway (2), France (2), Romania (1), and Belgium (1). At least one child has died following a bout of severe hepatitis, with 10 in the UK requiring liver transplants, and a further case has been reported in China.
A probable cause for the liver inflammation is emerging, as health authorities around the world investigate.
"Information gathered through our investigations increasingly suggests that this rise in sudden onset hepatitis in children is linked to adenovirus infection," Dr Meera Chand, Director of Clinical and Emerging Infections at the UK Health Security Agency (UKHSA) said in an update. "However, we are thoroughly investigating other potential causes."
Adenoviruses have been found in at least 74 cases according to the WHO, with 18 identified as adenovirus F type 41 – a type that hasn't been associated with liver damage previously. In the UK, where most cases have so far occurred, Adenovirus has been found in 75 percent of those children tested. Sixteen percent also tested positive for COVID-19, though the UKHSA stressed that COVID-19 was prevalent during the time of admission, so this was not unexpected.
Though adenovirus, particularly adenovirus F type 41, is emerging as the likely cause of the liver inflammation, it's still unclear by what mechanism. The type is associated with gastroenteritis illness in young children, according to Professor Will Irving of the University of Nottingham, who is not involved in the research, but has not previously been associated with the liver damage in otherwise healthy children that has been seen over recent months.
"The link with adenovirus infection remains tantalising – a definite possibility but not yet proven," Irving said.
"There are very few case reports in the global literature of adenovirus infection being associated with hepatitis in immunocompetent children (or adults) – so if it transpires that adenoviral infection is involved in causing this disease outbreak, there will be a need to explain why the natural history of adenovirus infection has changed so dramatically in 2022.”
Though adenovirus 41 is emerging as a likely culprit, the WHO stresses that further information about cases – including their close contacts – is needed before conclusions can be drawn. One possibility is that decreased contact between children due to COVID-19 restrictions has played a part in the cases.
“Adenoviruses are viruses that can normally cause the common cold in adults, but also diarrhea, abdominal pain, and vomiting in children. Sometimes symptoms can be more severe and can rarely cause liver inflammation. It is not uncommon to have adenoviruses in springtime," posited Prof Simon Taylor-Robinson, Hepatologist at Imperial College London.
"Given their seasonality, it may be that the past two years has seen children isolated away from their peers and thus not contracting the usual childhood viral illnesses that build up immunity. Thus, contact now to viruses like adenoviruses may account for the more exaggerated symptoms of some of these previously isolating children."
The number of cases remains small, but the UKHSA say carers should be aware of the symptoms just in case.
"Parents and guardians should be alert to the signs of hepatitis (including jaundice) and to contact a healthcare professional if they are concerned. Normal hygiene measures such as thorough handwashing (including supervising children) and good thorough respiratory hygiene, help to reduce the spread of many common infections, including adenovirus," Dr Chand said.
"Children experiencing symptoms of a gastrointestinal infection including vomiting and diarrhoea should stay at home and not return to school or nursery until 48 hours after the symptoms have stopped."
The health agency also stressed that, contrary to speculation online, no link has been found to COVID-19 vaccination.
"There is no link to the coronavirus (COVID-19) vaccine," the UKHSA said in the update. "None of the currently confirmed cases in under 10-year-olds in the UK is known to have been vaccinated."