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New hepatitis in children, which is true of 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 relationship has been verified.

It is news of 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, in the United Kingdom – where the first cases were recorded – it is being thoroughly investigated, without excluding any other hypothesis. In a recent technical briefing, in particular, the UK Health Safety Agency (UKHSA) reported a relatively high number of “dog exposures” in children affected by this severe form of hepatitis. However, 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, the UKHSA found that 70% of young patients (64 out of 92 for whom data was available) were from families with dogs or had been “exposed to other dogs”. These data, from questionnaires completed by the parents of children affected by hepatitis, are however not sufficient to demonstrate a causal link, as explained by Mick Bailey, professor of comparative immunology at the University of Bristol. ” To suggest a link – says the expert one The conversationit is important to show not only that exposure to dogs in patients is high, but that it is higher than in unaffected children. Until a link is verified in what’s called a case-control study, any link is nothing more than a hypothesis.“.

This hypothesis, among others, is “extremely weak, probably much lower than most of the other alternative hypotheses that have been proposed”, added Bailey, highlighting how, with 33% of families in the UK owning dogs, having 70 % of children with hepatitis have come into contact with a dog »it can be completely normal » considering also that “many other children from non-dog-owning families will be exposed to dogs when they visit or play with their friends“.

A 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 linked to cases. This type of connection is called parasitic correlation, and several examples of this type of association are presented on a dedicated site. 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 correlation. (Tiler Vigen)

The important point about the links identified by the back data is that they are hypotheses – explains Bailey -. They should always be verified by collecting additional data on new cases. If the link is real, it will continue to appear in new data. If it’s wrong, it won’t 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 linked to deaths from entanglement in sheets. ” 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 may be true, even if the mechanism is rather wacky.“.

Possible causes of acute hepatitis in children

As noted, the main hypotheses about the causes of this form of pediatric hepatitis are those involving one virus in particular, an adenovirus, which was detected in 72% of patients tested (for comparison, Sars-Cov-2 n was detected in only 18% of cases). ” When the type could be identified, the pathogen turned out to be adenovirus 41 (Ad41), a viral form that infects humans and normally causes diarrhea in children. – indicates Baily -. 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 do occur do not suggest 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 similarly, 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 a canine virus would spread among dogs“.

Other possible causes of pediatric acute hepatitis

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

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

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