Scientists puzzle over Covid pandemic link to childhood hepatitis cases

After spending two years studying data to explain the coronavirus, public health officials are now trying to understand an unexpected increase in hepatitis cases in healthy children that is popping up in a growing number of countries.

Canada and Japan joined more than a dozen other countries in reporting outbreaks this week as major health agencies, including the World Health Organization and the European Center for Disease Control and Prevention, began investigations into the nearly 200 known cases.

Theories about the origin of the mysterious illness, which involves severe liver inflammation and led to at least 17 children requiring transplants, have multiplied since UK health authorities first raised the alarm in early April. One child has died so far, according to the WHO.

Many scientists looking for the causes of the outbreak have focused on the role played by the coronavirus pandemic. Experts have hypothesized that the disease could be linked to a decline in immunity to adenovirus, a cause of the common cold, due to two years of pandemic-related restrictions, the aftereffects of a coronavirus infection, or even a mutated form of one of those viruses.

“Whatever theory you subscribe to, this must stem from the massive public health event of the past two years,” said Alastair Sutcliffe, a professor of general pediatrics at University College London. “It’s too much of a coincidence — either it’s a drop in immunity to adenovirus or the adenovirus is partnering with Covid to cause hepatitis, but the pandemic must play a role.”

Countries in the Northern Hemisphere have recorded an increase in common viruses – such as adenovirus, rhinovirus and chickenpox – since pandemic countermeasures were eased this winter, while also recording record high Covid infection rates.

Will Irving, a professor of virology at the University of Nottingham, said it was possible that “the blank slate of immunity” left by reduced social mixing, as countries went into lockdown and schools closed, the effects of the adenovirus would become “more destructive.” can make.

“It can be important at a young age to meet a whole host of viruses and sort yourself out, and that hasn’t happened,” says Irving.

But scientists have warned against jumping to conclusions.

Adenovirus – a group of viruses typically associated with symptoms such as persistent cough, conjunctivitis or diarrhea – very occasionally causes hepatitis, but almost never in healthy children.

“People speculate until they’re blue in the face, but all we have is a bunch of correlations and no apparent cause,” said Isaac Bogoch, an associate professor of medicine at the University of Toronto in Canada.

With the UK accounting for about three-fifths of known cases, British scientists are leading the way in researching the disease. Of the 53 British children tested for adenovirus, 40 gave positive results. But 16 per cent of the more than 100 cases in the UK also tested positive for Covid-19 at admission, compared with a community infection rate of between 5 and 8 per cent over the same period.

“There is some evidence, but there is still a lot of scientific detective work to be done,” said Deirdre Kelly, a professor of pediatric hepatology at Birmingham Women’s and Children’s Hospital, which has treated the largest group of patients.

Philippa Easterbrook, a medical expert in the WHO’s Global HIV, Hepatitis and Sexually Transmitted Infection Program, told a news conference this week that the idea that adenovirus may have led to more serious infections because they had been suppressed during the lockdown, “is an interesting one.” review was of the data, but it really needs to be followed up with more studies.”

Covid-19 vaccinations have been ruled out as a possible cause, as the disease mainly affects children under 10 – few of whom have received a shot.

The first known cases of the mysterious hepatitis were recorded in the US state of Alabama between November 2021 and February this year. Five of the nine children tested positive for adenovirus, while none of them showed any signs of current or previous Covid infection. Last week, the U.S. Centers for Disease Control and Prevention issued a warning about the disease, and seven states are now investigating possible cases.

“When … this was presented to me, I said I had never seen a cluster like this in my career,” said Dr. Karen Landers, medical director of the Alabama Department of Health, who has spent more than four decades in the community. public health works.

Professor Jeffrey Lazarus, head of the Health Systems Research Group at the Barcelona Institute for Global Health, said the “long list” of symptoms linked to Covid-19 suggested there may have been a previous coronavirus infection. “There has been a whole range of Covid symptoms. It wouldn’t surprise me at all if there’s an extra one,” he said.

Experts believe that a previous Covid-19 infection can weaken the immune system, leading to a more severe reaction to the adenovirus.

In the UK, genomic sequencing analysis is performed on adenovirus samples from patients to determine if the virus has adopted mutations that can lead to hepatitis. Tests for Covid antibodies are also underway.

However, Lazarus warned that some experts “are not using the weapon based on what their thoughts were about Covid restrictions”. “The commentary is ahead of science. Let’s give science time to catch up.”

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