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Acute Hepatitis of Unknown Aetiology in Children in the Western Countries Amidst the COVID-19 Pandemic— Could it be the Culprit?

The UK Health Security Agency (UKHSA) reported on 21 April that 34 new cases of unexplained acute hepatitis in children have been detected in the UK since the 74 cases in young children on 8 April, bringing the total number of cases to 108.

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Source: Department of Health and Social Care — GOV.UK

In fact, not only the UK, but also Spain, Ireland, Denmark, the Netherlands, France, the United States and many other countries in Europe, have also identified similar cases, which have attracted the attention of the WHO. 

1. Symptoms of Acute Hepatitis of Unknown Aetiology

Eight children in the UK have now undergone liver transplants due to the severity of their illness. It is understood that the infected patients are all children under 10 years old, with no history of travel outside the country and previous illnesses. The earliest case presented with symptoms in January 2022 and the clinical signs were mainly acute hepatitis, markedly elevated liver enzymes, usually with jaundice, and sometimes gastrointestinal symptoms.

Acute hepatitis of unknown aetiology, meaning that the cause of the disease is not yet clear and the common viruses that cause infectious hepatitis (hepatitis A to E) have not been detected in patient samples. So what exactly causes it?

Public health doctors and scientists are actively investigating the cause, including coronavirus (COVID-19), other infections or environmental causes. However, through testing of patient samples, it is found that 77% of cases tested were positive for adenovirus, and some samples were detected for neo-coronavirus. In addition, a small number of children tested positive for coronavirus shortly before or on admission to hospital and none had been vaccinated, so the effect of the vaccine could largely be ruled out.

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Source: Department of Health and Social Care — GOV.UK

More and more public health experts and scientists now believe that adenovirus or its variants are the “most likely” trigger for this acute hepatitis of unknown aetiology. 

2. What is an Adenovirus?

Adenovirus is a double-stranded DNA virus without an envelope, with a symmetrical 20-sided structure and a diameter of about 70 to 90 nanometres, which reproduces mainly inside cells. It is usually transmitted through respiratory droplets or close contact. 4% to 10% of pneumonia is caused by adenovirus infection, especially in young children under 5 years old.

Diagram of Adenovirus from the Internet

UKHSA reported that although adenovirus does not usually cause hepatitis, it is a rare viral complication.

3. Is Adenovirus the Most Likely Trigger?

Reports of adenovirus causing hepatitis were seldom in the past, but this possibility still can’t be excluded.

Generally speaking, adenovirus infections mainly cause infections of the respiratory and digestive systems of humans. In addition, the central nervous system, the circulatory system, the blood system of human beings also can accumulate adenovirus and almost all organs have tested it before. Stanford University once reported 12 cases of adenoviral hepatitis in immunocompromised people.

As for animals, adenovirus-induced hepatitis is relatively more common. For example, canine infectious hepatitis is an acute septic infection of dogs caused by canine adenovirus type I. This virus mainly infects puppies, foxes, wolves, raccoons, mink groundhogs and so on.

Although the neo- coronavirus has also been detected in some case samples, several infection specialists and paediatric medicine experts believe that there lies a low possibility that the neo- coronavirus directly infects hepatitis. Nevertheless, the isolation measures during the COVID-19 may lead to a decrease in children’s immunity to fight against the virus, increasing the risk of infection of the adenovirus.

It is considered that viruses have their own “intelligence” and can evolve according to their receptors, finding themselves a more suitable access to survive. For example, the neo-coronavirus evolved from the original strain to the Omicron variant, which is actually an evolution from lung to nose. The pathways of infection are similar for neo-coronaviruses and adenoviruses, and it is possible that adenoviruses could find a more suitable pathway and attack the liver, which is less “favoured” by neo-coronaviruses (with fewer or less active neo-coronavirus receptors AEC2 in the liver). It is significant to understand that human hepatitis, such as A, B, C, D, and E (HAV/HBV/HCV/HDV/HEV), are basically classified according to the “hepatophagy” of the virus, and not by genomic clustering like the coronavirus “family”.

Whether or not the acute hepatitis cases in western countries were caused by adenovirus remains to be verified by follow-up scientific studies and research.


Post time: Apr-27-2022