Since last April, cases of unidentified acute infantile hepatitis have appeared, without the cause being really identified. Just over 1,000 cases have been identified in 35 countries, according to the World Health Organization (WHO). The majority of affected children are under 6 years old. A total of 46 of them required a liver transplant and 22 died. In France, nine possible cases have been reported according to data communicated by Public Health France, and one is being investigated by the medical teams in charge of patients.

Initially, pediatricians and virologists suggested that adenovirus (a type of virus that causes upper respiratory tract infections, associated with flu-like illness) might be linked to the outbreak, with an association to that of the coronavirus.

However, two Anglo-Saxon studies, one British, conducted by the Great Ormond Street Hospital in London and the other Scottish, conducted by the University of Glasgow, are advancing new leads. Both rule out a Covid-19 infection. The coronavirus was not detected in the livers of the sick children studied, and the proportion of them showing antibodies against Covid-19 was similar to that of children not affected by these hepatitis.

It is another virus that these two studies point to: a common virus called AAV2 (adeno-associated virus 2). It has been detected at abnormally high levels in sick children. Nevertheless, this virus is not known to cause serious illnesses like the one observed. This is why British and Scottish scientists are leaning towards a co-infection of two viruses. That is, adenovirus 2 with another adenovirus or possibly with herpes virus (HHV6). “I think this is a plausible explanation for these cases,” said Deirdre Kelly, a professor of pediatric hepatology at the University of Birmingham, who was not involved in these studies, in a statement. “It seems that co-infection plays a key role.”

There are still a few questions to be clarified. Because the two studies, which have not yet been peer-reviewed, do not make it possible to say why certain children were infected. “We still do not understand why some children develop serious cases of the disease requiring a transplant. There would be a possibility that a co-infection with something other than a virus “is responsible, explained to AFP the Pr Deirdre Kelly. Another hypothesis is the discovery of a completely new virus at the origin of these infections.

Scientists also do not clearly understand why these cases are appearing precisely now. Among the plausible hypotheses: the idea that the confinements linked to the coronavirus have had an influence, for example by modifying the usual circulation of other viruses, or by preventing children from creating certain defenses against viruses with which they have been less confronted.

At the end of April, the European Center for Disease Control and Prevention (ECDC) said it was worried about the number of cases of these mysterious hepatitis. “Considering the etiology [Editor’s note: the cause of the disease] still uncertain, the affected pediatric population, and the potentially serious impact, this constitutes at this stage a worrying public health event”. In France, “a standardized information feedback system involving a network of clinicians and laboratories has been set up to detect a possible similar signal on the territory”, indicates Public Health France.