In the months since UK physicians sounded the alarm about mysterious cases of hepatitis that seemed to be striking young children, researchers have been scrambling to determine the cause — and a possible connection to the coronavirus pandemic has been among the leading hypotheses.
But on 17 June, researchers at the US Centers for Disease Control and Prevention (CDC) published data suggesting that — in the United States, at least — rates of hepatitis, or liver inflammation, with an unknown cause had not changed since 2017 among children aged 11 or younger1. If true, the finding could confound the pandemic-link theory.
Hepatitis in children has several known causes, including infection by viruses such as hepatitis A, and exposure to certain medications, such as paracetamol. But every year, a few cases of unexplained pediatric hepatitis occur.
Over 1,000 probable cases of unexplained severe acute hepatitis in children have been recorded in 35 countries since the outbreak was first detected in April, the World Health Organization said on Tuesday.
As of July 8, 1,010 cases have been recorded and 22 children have died. Almost half of the probable cases were reported in Europe, accounting for 484 cases (recorded in 21 European countries), followed by 435 cases in the Americas (334 recorded in the US alone), and 272 cases in the United Kingdom.
17 countries have so far reported over five probable cases. “The actual number of cases may be underestimated, in part due to the limited enhanced surveillance systems in place. The case count is expected to change as more information and verified data become available,” WHO cautioned in a statement on Tuesday, adding that the risk of this pediatric hepatitis outbreak spreading is “moderate.”
The United Nations health agency has been keeping a close eye on the matter – in addition to dealing with the COVID-19 and monkeypox outbreaks – as the spread of the mysterious virus has left dozens of previously healthy children in need of liver transplants.
The most commonly reported symptoms were nausea or vomiting, jaundice, general weakness, and abdominal pain, according to the currently available clinical data. The average time between exhibiting symptoms and hospitalization was four days.
The health body said that hepatitis A to E was not present in the affected children who underwent laboratory testing. Other pathogens such as the coronavirus were detected in some cases, but the data is incomplete.
WHO said the “most frequently detected pathogen” however were adenoviruses – a virus which causes a wide range of illnesses like fever, colds, pneumonia, and sore throats.
“Due to limited adenovirus surveillance in most countries, it is challenging to assess whether these rates are higher than the expected rates in the population,” the UN health body said.
Adenoviruses – which cause a wide range of illnesses, such as colds, fever, sore throats, and pneumonia – have been “the most frequently detected pathogen” in cases of pediatric hepatitis, WHO said.
In Europe, adenovirus was detected by polymerase chain reaction tests (PCR) in 52 percent of the child hepatitis cases (193/368) so far; in Japan, it was found in just nine percent of cases (5/58).
According to UN News, owing to limited adenovirus surveillance in most countries, the true number of cases of child hepatitis may be higher than currently known.
The cause remains unknown:
Hepatitis is an inflammation of the liver usually caused by a viral infection or excessive drinking of alcohol. There are several common types, such as A, B, C, D, and E, all of which have varying levels of contagion or cause, but these common viruses from A to E have not been detected in any of these cases.
“It could be a new virus, it could be just a form of liver disease caused by something else,” James said. Several hypotheses are being studied to understand the cause of this hepatitis in these children. Adenovirus remains one of the main suspects, as it has been the most frequently detected virus in samples tested in the UK.
“The current leading hypotheses concern adenovirus involvement, possibly with a cofactor that is triggering a more severe infection or immune-mediated liver damage, or that measures during the COVID-19 pandemic have resulted in lack of exposure for the youngest age group and increased susceptibility,” said a report by the European Centre for Disease Control (ECDC).
A link to the COVID-19 vaccine is considered unlikely as most cases have been unvaccinated. The disease pathogenesis and routes of transmission remain unknown. The cases appear to be unrelated, with very few being epidemiologically linked.
“While the risk for further spread cannot be accurately assessed, as some cases have required liver transplantation, the potential impact for the affected pediatric population is considered high,” the ECDC report said.