Why COVID is a key suspect in severe hepatitis cases in kids worldwide

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Unexplained severe acute hepatitis cases among children continue to emerge in Canada and around the world, and while health officials desperately search for a cause of the mysterious illness, researchers are pointing to a possible link to COVID-19. 

The World Health Organization (WHO) said Tuesday there are now at least 348 probable cases of severe acute hepatitis —  or inflammation of the liver — in children under investigation worldwide, which aren't caused by the usual hepatitis viruses or any other clear source.

In Canada, more than a dozen possible cases have been reported across multiple provinces since the Public Health Agency of Canada (PHAC) confirmed earlier this month that some cases of the severe liver disease were under investigation.

While an early line of investigation from U.K. health officials emphasized possible links to adenovirus, a family of viruses typically known for causing mild cold or flu-like illness, global teams are also zeroing in on potential impacts from SARS-CoV-2, the virus behind COVID-19.

A recent American case study published in the Journal of Pediatric Gastroenterology and Nutrition analyzed a previously healthy three-year-old girl who developed acute liver failure a few weeks after recovering from a mild COVID infection. 

"The patient had liver biopsy findings and blood testing consistent with a type of autoimmune hepatitis which may have been triggered by COVID infection," said Dr. Anna Peters, a pediatric gastroenterologist at the Cincinnati Children's Hospital Medical Center.

Peters, the lead author on the study, said that while it was impossible to prove that COVID directly caused the liver disease in this case — it is possible the virus triggered an "abnormal immune response" that then attacked the liver.

"I think it's important for physicians to be aware that this is a rare condition that may happen during or after COVID infection. It's important to check liver tests in patients who aren't improving as expected," she said.

"Parents shouldn't panic, but see their pediatrician or primary care doctor if their child is ill. Prompt diagnosis and provision of supportive care is key to recovery."

Peters said the patient in the case study did recover after treatment and a liver transplant was avoided, but that the case may be similar to cases reported in the U.K. and globally.

Israeli physician Dr. Yael Mozer Glassberg previously told CBC News that her team at Schneider Children's Medical Center has also treated at least eight unexplained cases of hepatitis since Feb. 2021, before the WHO's starting point of Oct. 2021 for "probable" cases.

Medical staff analyzed those cases and the only commonality was that each child had faced a previous bout of COVID-19, identified through serological testing and each family's medical history. None of the patients tested positive for adenovirus, Mozer Glassberg said.

An Indian research team also studied whether COVID-19 may have caused dozens of unexplained cases of severe acute hepatitis in children in Central India between April and July 2021, and their results are only now gaining attention due to similar cases worldwide.