New hepatitis in children, this applies to the hypothesis of contact with dogs

Data published in the UK shows that 70% of children with this severe form of hepatitis have had contact with a dog, but so far no causal relationship has been ascertained.

It’s news these hours that there is a possible link between new and mysterious acute hepatitis in children and contact with dogs. Although the data available so far suggest that the likely cause is an adenovirus, in the UK – where the first cases were recorded – it is being thoroughly investigated, without ruling out any other hypothesis. In a recent technical briefing, in particular, the UK Health Safety Agency (UKHSA) reported a relatively high number of ‘canine exposures’ in children with this severe form of hepatitis. However, before this leads to unnecessary frightening excitement, it is useful to understand what has already been observed in the UK.

Acute hepatitis in children and the ‘link’ to dogs

In the article, the UKHSA found that 70% of young patients (64 of the 92 for which data were available) were from families with dogs or were ‘exposed to other dogs’. These data, from questionnaires completed by parents of children with hepatitis, are not enough to establish a causal link, explained Mick Bailey, professor of comparative immunology at the University of Bristol. ” to suggest a link – says the expert dialogueIt is important to show that not only is exposure to dogs high in patients, but that it is higher than in uninfected children. Until the association is verified in the so-called case-control study, any association is nothing more than a hypothesis.“.

This hypothesis is, among other things, “very weak, and probably much less than most other alternative hypotheses that have been proposed”, Bailey added, explaining how 33% of families in the UK own dogs, and 70% of them have children. Hepatitis in contact with a dog »It can be completely normal » Bearing in mind also that “many other children from families without dogs will be exposed to dogs when they visit their friends or play with them.”“.

The second problem, the expert points out, is that when large amounts of data are collected retrospectively, there is a risk that some of it may appear to be case-related. This type of connection is called a parasitic link, and many examples of this type of link are given on a dedicated site. For example, the divorce rate in Maine between 2000 and 2009 appears to be closely related to per capita consumption of margarine (graph below).

wrong link. (Tiller Vision)

The important point about the links identified by the background data is that they are hypotheses – Explains Bailey. They should always be verified by collecting additional data on new cases. If the correlation is real, it will continue to appear in the new data. If it’s wrong, it won’t be“.

Another association on the False Correlation website shows another important issue. Between 2000 and 2009, per capita cheese consumption in the United States appears to be associated with deaths from platelet entanglement. ” It’s not really hard to think that this could happen because of cheese nightmares. – Expert jokes -. The fact that we can think of a mechanism behind the link gives us more confidence that it might be correct, even if the mechanism is somewhat strange.“.

Possible causes of acute hepatitis in children

As indicated, the main hypotheses about the causes of this form of hepatitis in children are those involving one virus in particular, adenovirus, which was detected in 72% of the patients tested (for comparison, Sars-Cov was detected -2n only in 18% of cases). ” When the species can be determined, the pathogen has been shown to be adenovirus 41 (Ad41), a viral form that infects humans and naturally causes diarrhea in children. Billy points out. Although dogs have their own adenoviruses that cause respiratory disease or hepatitis, these viruses are not known to infect humans and Ad41 has no known association with dogs.“.

On the other hand, the cases that occur do not suggest the spread of infection among children. ” Cases are too few and widespread to assume that the infection will spread among children. Likewise, the distribution of cases also does not suggest that this is a new virus transmitted from dogs to children. Cases have appeared in other countries much faster than the spread of the canine virus among dogs“.

Other possible causes of acute hepatitis in children

Some experts have suggested that the severity of this form of hepatitis may be due to an immune cause indirectly related to the COVID-19 pandemic. ” Social distancing during a pandemic has reduced transmission of various diseases, and lack of exposure may leave some children unprepared for infections that usually do not cause problems. – Billy thinks -. Likewise, lack of exposure to dirt from hand washing, disinfecting surfaces, and other hygiene measures may predispose children to highly reactive immune responses (as suggested for allergies) and hepatitis, which can be triggered by an immune system response instead. from a virus. Finally, and unsurprisingly, it has been suggested that previous Covid infection may be susceptible to hepatitis“.

Currently, all of these hypotheses are merely hypotheses and there is not enough data available to prioritize any of them or to suggest control measures. The expert concludes. Fortunately, the infection rate is still very low, and until better data is available, parents should focus more on monitoring symptoms in their children rather than reducing their exposure to dogs.“.

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