New hepatitis in children, which is true for the dog contact hypothesis

Data published in the United Kingdom show that 70% of children with this severe form of hepatitis have had contact with a dog, but to date no causal link has been verified.

It is news in these hours that a possible link between the new and still mysterious acute hepatitis in children and contact with dogs. Although the data available to date seem to suggest that the possible cause is an adenovirus, it is being thoroughly investigated in the UK – where the first cases were recorded – without ruling out any other hypothesis. In a recent technical briefing, the UK Health Safety Agency (UKHSA) in particular reported a relatively high number of “dog exposures” in children affected by this severe form of hepatitis. But before this leads to unnecessary alarmism, it is useful to understand what has actually been observed in the UK.

Acute hepatitis in children and the “connection” with dogs

In the article, UKHSA found that 70% of young patients (64 out of 92 for whom data were available) were from families with dogs or had been “exposed to other dogs”. However, these data, from questionnaires completed by parents of children with hepatitis, are not sufficient to demonstrate a causal relationship, as explained by Mick Bailey, Professor of Comparative Immunology at the University of Bristol. ” To suggest a link – says the expert The conversationit is important not only to show that exposure to dogs in patients is high, but that it is higher than in unaffected children. Until a link is verified in what is called a case-control study, any link is nothing more than a hypothesis.“.

This hypothesis is among others “extremely weak, probably much lower than most of the other alternative hypotheses that have been proposed”, Bailey added, highlighting how 33% of families in the UK own dogs and that 70% of children with hepatitis has come into contact with a dog »it can be completely normal » also considering that “many other children from families who do not own dogs will be exposed to dogs when they visit or play with their friends“.

Another problem, the expert points out, is that when large amounts of data are collected backwards, there is a risk that some of it may appear to be linked to cases. This type of connection is called parasitic correlation, and several examples of this type of connection are presented on a dedicated website. For example, the divorce rate in Maine between 2000 and 2009 appears to be strongly related to per capita margarine consumption (chart below).

A false connection. (Tiler Vigen)

The important point of the links identified by the feedback data is that they are hypotheses Bailey explains. They should always be verified by collecting additional data on new cases. If the link is genuine, it will continue to appear in new data. If it’s wrong, it will not be“.

Another of the associations on the False Correlation website shows another important problem. Between 2000 and 2009, per capita cheese consumption in the United States appears to be associated with deaths due to sheet infiltration. ” It’s actually not hard to think that it can 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 can be true even though the mechanism is pretty crazy.“.

Possible causes of acute hepatitis in children

As indicated, the main hypotheses about the causes of this type of pediatric hepatitis are those involving one virus in particular, an adenovirus, which was detected in 72% of the patients tested (in comparison, Sars-Cov-2 n was detected in only 18% of patients). cases). ” Since the type could be identified, the pathogen turned out to be adenovirus 41 (Ad41), a viral form that infects humans and usually causes diarrhea in children. Indicates Baily -. Although dogs have their own adenoviruses that cause respiratory diseases 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 do occur do not indicate that the infection is spreading among children. ” The cases are too few and too widespread to assume that the infection is spreading among children. And in the same way, the distribution of cases does not indicate that it is a new virus that is transmitted from dogs to children. Cases have emerged in other countries much faster than a canine virus would spread among dogs“.

Other possible causes of pediatric acute hepatitis

Some experts have suggested that the severity of this type of hepatitis may be due to an immune cause, indirectly linked to the Covid pandemic. ” Social distancing during the pandemic has reduced the transmission of various diseases, and lack of exposure to them may have made some children unprepared for infections that would not normally cause problems. – Baily thinks -. Similarly, lack of exposure to dirt from hand washing, sterilization of surfaces, and other hygiene measures may have predisposed children to hyperreactive immune responses (as has been suggested for allergic diseases) and hepatitis, which may be caused by the immune system’s reaction rather than a virus. Finally and not surprisingly, it has been suggested that previous Covid infections may have predisposed children to hepatitis“.

At present, all of these hypotheses are hypotheses only and there is insufficient data available to prioritize any of them or propose control measures. Concludes the expert,. Fortunately, the incidence is still extremely low, and until better data become available, parents should probably focus more on monitoring symptoms in their children rather than reducing their exposure to dogs.“.

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