Just before World Hepatitis Day on July 28, when the World Health Organization (WHO) draws attention to the dangers of viral liver inflammation, two studies are appearing that seem to have come a little closer to the cause of the mysterious cases of hepatitis in children .

Johanna Kuroczik

Editor in the "Science" department of the Frankfurter Allgemeine Sunday newspaper.

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In April of this year, the first medical histories in Scotland made headlines – an unusually large number of children were suffering from severe liver inflammation.

Since then, more than 189 severely affected children have had to be treated in hospitals in England, and twelve have needed a liver transplant.

By the beginning of July, the WHO counted more than 1,010 suspected cases in 35 countries, half of them in Europe.

Many children were younger than five years.

A total of five percent of the sick, i.e. 46 children, would have had to have a donor organ transplanted and 22 children had died.

What is striking is not only the relative frequency of cases, but also their severity.

Liver inflammation in young children is usually rather inconspicuous.

Elevated liver enzymes, transaminases, such as alanine aminotransferase, are noticeable in the blood count.

Children with severe illness suffer from abdominal pain, vomiting and fever.

The skin and whites of the eyes may appear yellowish and the stools may be discolored.

The corona virus does not seem to play a causal role

Since the first cases appeared, doctors have been looking for the pathogen.

Inflammation of the liver caused by viruses is often due to one of the so-called hepatitis viruses A, B, C, D or E.

There are some effective vaccinations and also proven test procedures against these.

However, these were negative in the sick children in England.

SARS-CoV-2 was quickly suspected as the culprit, but the affected children were not significantly more likely to be infected with the coronavirus than the general population.

For the past month, experts have been looking at another virus: adenovirus 41F, which has often been detected in affected children – but not in the destroyed liver cells.

Two recent studies now point to another pathogen.

Various research centers from England were involved in the research work, which has so far only appeared as a preprint and has therefore neither been reviewed by peers nor published in a specialist journal - leading researchers from the Medical Research Council at the University of Glasgow and the University College in London.

They used DNA sequencing and immunohistochemistry methods to examine tissue samples from some sick children.

In the study from Scotland, 28 samples from those affected were examined and compared with 136 control samples; the British study included data from 9 patients and 58 control samples.

These children were either healthy or had hepatitis from other causes.

A virus called AAV2 – the adeno-associated virus 2 – was found in almost all those affected. These dependoviruses are dependent on other viruses: they need certain proteins, mostly from adenoviruses, in order to multiply.

The virus was hardly detected in the children in the control group, in Scotland in six percent of the blood samples.