Severe hepatitis of 'unknown origin' in children being investigated in Canada
Unclear if reports linked to unexplained outbreak of more than 160 cases
Public health officials say they're investigating cases of severe liver disease "of unknown origin" among children in Canada as global scientists race to understand a mysterious hepatitis outbreak that has affected nearly 200 youths around the world.
"The Public Health Agency of Canada is aware of reports of severe acute hepatitis of unknown origin in young children in Canada," the department said in a statement on Tuesday, in response to questions from CBC News.
"These are being investigated further to determine if they are related to cases in the United Kingdom and the United States. As the investigation evolves, we will keep the public updated accordingly."
The latest available data from the World Health Organization (WHO) shows at least 169 cases of acute hepatitis of unknown origin have been reported in close to a dozen countries, with the bulk of the reports — 114 — from the U.K.
On Tuesday, the European Centre for Disease Prevention and Control (ECDC) released an even higher estimate of nearly 200 cases in children around the world.
The U.S. has identified more than a dozen cases across several states, with instances of unexplained hepatitis also occurring in Spain, Israel, Denmark, Ireland, Italy, Norway, France, Romania, Belgium and the Netherlands.
Roughly 10 per cent of the affected children have required liver transplants, WHO data shows, and at least one child has died.
It's not yet clear if the Canadian cases are the same syndrome seen elsewhere, says liver disease specialist Dr. Jordan Feld, a senior scientist at the Toronto General Hospital Research Institute.
Affected children typically have gastrointestinal symptoms such as nausea, vomiting and diarrhea, he said.
"But then the more severe issue is that they're developing jaundice … or found to have abnormal liver blood tests," Feld said.
"At this stage, it would just be prudent if children have some of these symptoms, particularly if they seem to be more severe, that they're seeking medical attention."
Officials have not yet provided details on the total number of Canadian cases.
The cases reported worldwide have struck children from one month to 16 years old.
What's perplexing, scientists tell CBC News, is what could be causing them.
"Certainly a viral infection is high on the list, but is definitely yet to be proven," Feld said.
Various medical conditions and medications can cause hepatitis; so can heavy alcohol use or exposure to certain chemicals or drugs. But most often, inflammation or damage to the liver is caused by a virus.
However, the usual family of hepatitis viruses haven't been identified in any of the cases tied to the current global outbreak, the WHO said.
An adenovirus was detected in at least 74 cases; a common group of viruses known for causing a wide range of health issues, from gastrointestinal upset, to bladder infections to the common cold.
In the U.K. officials recently observed a significant increase in adenovirus infections in the community following low levels of circulation earlier in the COVID-19 pandemic.
ECDC director Andrea Ammon told reporters that one theory suggests pandemic lockdowns may have weakened children's immunity because they were less exposed to common pathogens while in isolation.
But it's hardly definitive, given the different rates of testing for various viruses.
The virus behind COVID-19, SARS-CoV-2, was also identified in 20 cases of those that were tested — while 18 of the young patients with hepatitis were infected with both viruses.
In Israel, one of the physicians involved in treating child hepatitis cases suspects there may be a connection to COVID-19.
"After we ruled out all the various possibilities, the common denominator in all the cases we found was that all had come down with the coronavirus around three and a half months before the infection appeared," Dr. Yael Mozer-Glassberg, head of the pediatric liver transplantation unit at Schneider Children's Medical Center in Petah Tikva, told Israel media outlet Haaretz.
"This certainly raises the question. But I don't think it's possible to say yet that all these cases are a post-COVID phenomenon."
The cause may wind up being linked to an adenovirus, or SARS-CoV-2, or some interaction between an environmental exposure and a virus, said Dr. Isaac Bogoch, an infectious diseases specialist with the University of Toronto.
"We are in the middle of a pandemic — but you cannot have what we call an 'anchoring bias' where we say it's got to be COVID," he said. "Certainly might be. But you've got to keep an open mind."
Given the ages of the children impacted, Dr. Allison McGeer, an infectious disease specialist in the Sinai Health System in Toronto, said one potential cause that can be easily ruled out is COVID-19 vaccination. Most young children, she noted, aren't yet able to get vaccinated.
Whatever the cause, scientists are on high alert for more reports of children falling ill.
"Any time we see severe hepatitis, particularly in young children, it's alarming," Feld said.
With files from Adam Miller, Marcy Cuttler, Christine Birak, Reuters