“Mysterious” cases of hepatitis in children leave scientists confused

Dozens of children in Europe and the United States have been infected with acute hepatitis of unknown origin since early April. European health authorities have begun investigating this mysterious disease, which in a few rare cases has required a liver transplant. The point of several experts based in the UK where the first cases were discovered.

“Very strange”, “extremely surprising” or even “really unusual and disturbing”. These are the qualifications used by virologists and pediatricians interviewed by France 24 about the appearance for almost a month in young children of cases of hepatitis – that is, inflammation of the liver – of unknown origin.

The European Center for Disease Prevention and Control announced on Tuesday, April 19, that it had observed it in five European countries. The first infections go back to early April in Scotland. Then children became ill in the rest of the British Isles. There have officially been just under 80 patients – aged between 22 months and 13 years – in the UK, according to the UK Health Safety Agency, which opened a study on the phenomenon two weeks ago.

Very rare acute hepatitis in children

Since then, cases of hepatitis in children have been seen in Spain, Denmark and the Netherlands, according to the European Center for Disease Prevention and Control. Even the United States is affected as nine sick children have been treated in Alabama.

The number of infections certainly seems to be low in a world still battling a Covid-19 epidemic that has affected more than 500 million people. But that was enough to warn the World Health Organization, which has warned that the number of cases is expected to increase in the “coming days”, now that health authorities around the world are actively looking for them.

But the total number of affected children is not the most worrying factor for specialists. “What shocks me is, first of all, that hepatitis is a rather rare condition in children, and that in addition it is an acute case, which is even rarer,” sums up Will Irving, virologist at the University of Nottingham, contacted by France 24 .

Hepatitis often has causes that have nothing to do with the world of children. They can occur with excessive alcohol consumption, are transmitted during sexual intercourse if one partner is a carrier (hepatitis A) and are more common among injecting drug users who use uncleaned split needles (hepatitis VS).

In addition, the various forms of hepatitis are often benign, and the main symptoms – fever, diarrhea, abdominal pain, jaundice – subside or remain weak. That is not the case with this hepatitis, as “almost all children had severely damaged livers,” Will Irving emphasizes. Six of them even had to undergo a liver transplant, “which is very rare,” recalls Graham Cooke, a specialist in infectious diseases at Imperial College London, contacted by France 24.

To top it off, it’s currently a “mysterious” hepatitis. None of the main suspects – the viruses that cause hepatitis A to E – were found in the bodies of the young patients. No potential environmental factor common to all cases, such as food contamination or exposure to certain toxic substances (toxic hepatitis), could be identified at this stage.

The geographical distribution of cases – on both sides of the Atlantic – further reduces the chances of finding an explanation linked to a local environmental factor.

Link to Covid-19 unlikely

Pandemic obliges, Sars-CoV-2 virus has also been suspected. “Two hypotheses have been raised: either it is an still unknown effect of the latest Omicron variant, or we only now, after two years in which children were protected by confinement and other social distance measures, realize that Covid-19 can cause hepatitis in some adolescents, ”summarizes Alastair Sutcliffe, a pediatrician at University College London, contacted by France 24.

An association between coronavirus and these cases of acute hepatitis, which leaves this specialist skeptical. First, because several affected children were not infected with Covid-19 at the same time. So, if it were a still unknown symptom of Covid-19, “there would probably have been many more cases of hepatitis given the rate of spread of Sars-CoV-2,” assesses Will Irving.

British health authorities have even investigated whether it could be a negative effect of a vaccine against Covid-19. But none of the sick children were vaccinated. “That may be the only good news in this story. The antivax will at least not be able to grab it,” notes Alastair Sutcliffe.

There may also be a more indirect link to the pandemic. The successive incarcerations could have played a role, suggest all the experts interviewed by France 24. “We have an abnormal disease that occurs in an abnormal health context, it is logical to wonder if there is no connection “, emphasizes Alastair Sutcliffe. In this case, “children develop their immune system in contact with viruses, but for two years the youngest have been protected by confinement and distance measures, which means that their immune system has not adapted to certain viruses,” says Graham Cooke.

Trace of AD-41 adenovirus

Some even believe that they have identified a possible sinner: AD-41. It is an adenovirus – a large family of viruses, most often responsible for very mild symptoms such as colds or fatigue – “which is known to cause gastroenteritis in children, but which has not hitherto been associated with a risk of hepatitis”. notes Will Irving.

The presence of this adenovirus has been detected in several children affected by “mysterious” hepatitis in the United Kingdom, and “we know that there is currently a sharp increase in infections with this adenovirus in the British population”, recognizes Graham Cooke. “It’s pretty scary to think about the confinement and then the easing of sanitation [qui a permis de favoriser la propagation de l’adénovirus] may have led to the discovery of a new cause of hepatitis, ”notes Alastair Sutcliffe.

But again, nothing is certain. In fact, AD-41 was not present in all adolescents with hepatitis. “It’s not necessarily a refutation of the thesis of a link between this adenovirus and cases of hepatitis – we could not look in the right place, for example – but it weakens it,” Graham Cooke admits.

There is still the hypothesis of the discovery of a whole new virus at the origin of these infections. “It would still be extraordinary, given that we are still in a pandemic context, precisely because of a new virus,” assesses Alastair Sutcliffe. So much the more surprising given that we would go from a new virus that has been largely harmless to the youngest, to another pathogen that appears to target children, or at least cause severe forms exclusively in them.

This last hypothesis would be the easiest to verify. “We have advanced techniques for identifying the presence of foreign DNA or RNA – suggesting the existence of a virus – in tissues taken, in this case, from pieces of liver from infected children,” concludes Will Irving. On the other hand, if it is a matter of finding out if all these children were exposed to the same toxin or to a contaminated food, it becomes a much more complicated matter.

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