Canada is seeing an uptick in cases of unexplained hepatitis in kids. What does this mean?

Canada is reporting a higher number of children diagnosed with unexplained severe hepatitis, but experts remain cautious about whether this indicates a major increase in cases.

As of July 13, there were 24 cases of acute severe hepatitis in children not caused by known hepatitis viruses, according to the Public Health Agency of Canada (PHAC). This is up from 10 cases reported in May.

The children, who are between the ages of less than one year and 13 years old, became sick between Nov. 3, 2021 and June 29, 2022. All children were hospitalized and two children have required a liver transplant, according to PHAC.

Ontario is reporting the most cases at 13, Alberta has four cases, Quebec and Manitoba each have three and British Columbia has one.

A spokeswoman for PHAC says, while the number of cases has increased over the last two months, some of these cases may date back to fall of last year.

“On April 15, the World Health Organization issued a statement identifying multiple cases of acute severe hepatitis reported in several countries. This information prompted PHAC to ask provinces and territories to take a retrospective look at patients in their jurisdictions,” said Anne Genier, senior media relations adviser for Health Canada and PHAC.

“This process does take time, as we are asking clinicians to review case reports back to October 2021, and to collect additional information from patients that will inform PHAC’s national investigation.”

PHAC says it remains unclear if this represents an increase in cases of severe hepatitis among children in Canada, as baseline data for these incidents does not currently exist.

“We are analyzing Canadian hospitalization data to determine the number of cases that we would normally see in Canada over time,” PHAC says on its website.

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“This baseline information will allow us to determine if we are seeing an increase in cases reported.”

Hepatitis, or inflammation of the liver, is rare in children, but starting in early April of this year, the World Health Organization (WHO) has reported a mysterious rise in cases of acute hepatitis in kids. The outbreak was first reported in April in Britain and has since hit dozens of other countries.

Earlier this week, the WHO released a statement saying that as of July 8, a total of 35 countries have reported 1,010 probable cases, including 22 deaths — a jump of 90 new probable cases and four deaths since June.

Data from the UN agency shows most of the cases are in the United States and the United Kingdom and that laboratory testing has excluded normal hepatitis viruses A-E in these children, which is what has researchers struggling to explain the cause of the outbreaks.

The testing has also shown that adenovirus — a family of viruses that typically causes flu-like illness — has been detected in a number of these cases, although it remains unclear if this is triggering the hepatitis, according to WHO data. In Europe, adenovirus was detected in 52 per cent of hepatitis cases, but in only nine per cent of cases in Japan.

COVID-19 has also been detected in some of the children with severe hepatitis, including in 16 per cent of European region cases and eight per cent of U.S. and Japanese cases.

Whether COVID-19 or adenovirus is playing a role in these cases is still being studied by scientists, but it is clear the COVID-19 vaccine is not likely a culprit, says Dr. Simon Lam, an assistant professor at the University of Calgary Cumming School of Medicine and a pediatrician with expertise in caring for children with liver disease.

“Some of the parents in my clinic have asked, ‘Could the COVID vaccine be playing any role in triggering these episodes of hepatitis?’ And as you know, during that time when these reports have been coming out, kids less than five years old were not getting the COVID vaccine,” Lam said.

The vast majority of children coming down with this illness — 76 per cent, according to WHO data — are under six years of age and therefore ineligible for the COVID-19 vaccine. Also, among a group of 163 children in the U.K. who were positive for hepatitis, none of them had received the shot, he added.

“In my mind, I think that sends a pretty strong statement that the vaccine probably doesn’t have any role in either causing this or being related to the severe hepatitis in these kids.”

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Lam is among those taking a cautious approach to the reporting of these cases. Both he and the federal public health agency acknowledge the definition being used to include cases in the national investigation is “very broad.”

While many think of hepatitis in terms of the virus, other things can cause liver inflammation, including medications, metabolic conditions and autoimmune disorders, and the causes of these cases remain unknown, Lam said.

Also, while cases of severe hepatitis in children are considered rare, kids do go to the hospital with liver problems regularly, Lam added, and Canada, like other countries, hasn’t measured and studied this phenomenon as closely as it is now.

“It’s with this sort of increased recognition and increased surveillance that we’re now detecting these patients and sort of having a better idea of what our numbers are looking like now, but it’s really hard for us to say. Is this really an increase from last year or the year before?” he said.

“I think we’re doing the right thing. I think we’re keeping a close eye on things and reporting all our cases to the Public Health Agency of Canada. But it’s hard to know whether or not this is truly an increase sort of across Canada.”

The WHO has launched a global survey to estimate the incidence of severe hepatitis of unknown origin this year compared with the previous five years, with an aim to understand where cases and liver transplants are occurring at higher-than-expected rates, the UN agency said in its statement.