As sunshine and warm winds bring back the long-absent summer vibes to the northern hemisphere, most of the world is recovering from the year-long epidemic of SARS-COV-2. However, contagious diseases continue to haunt the public. Since the start of April, there have been reports of severe hepatitis in children and young teenagers.
As of 6th May, more than 300 cases have emerged in more than 20 countries across Europe, North America and Asia, claiming the lives of four children. In the UK, where the first cases were identified, there have been 163 cases with 11 liver transplants and one death.
Hepatitis refers to the acute inflammation of the liver, with the potential to cause damage to the organ, which is vital for digestion, detoxification, and metabolism. Cardinal symptoms of hepatitis include vomiting, dark urine, and jaundice (the yellowing of skin and sclera). Most cases of hepatitis are caused by viral infections, while autoimmunity and environmental factors may also play a role. In this instance, the identification of the cause of the hepatitis has become a big mystery troubling medical experts.
None of the most well-known viral strains, hepatitis viruses A to E, have been detected in affected children. Among various hypotheses being proposed, adenoviruses are believed to be the most likely culprit. Adenoviruses are widely circulating viruses among human populations, usually only causing infections in the respiratory or gastrointestinal tracts. There was no previous record of them leading to severe hepatitis, yet there seems to be a clear correlation. Both the UK Health Security Agency (UKHSA) and the Centers for Disease Control and Prevention (CDC) in the US report that a large proportion of infected children carry adenovirus, especially the two strains of AAV-2 and F41. Scientists are now examining these two types of adenovirus in more detail to confirm their pathogenic roles.
There have not yet been any clues as to the source of the virus causing the hepatitis. Some argued that pet dogs may be the origin, as 70 percent of infected children in the UK either live in households with dogs or have histories of contact with dogs. This view remains correlational, and has failed to gather much support from experts. As Prof. Francois Balloux from the UCL Genetics Institute explained, though adenovirus CAV-1 has been known to cause hepatitis in dogs, there is no evidence for their ability to infect humans.
Since the COVID pandemic has brought about so many changes to our lives, there have been speculations about its potential links with the current hepatitis. Health officials have so far ruled out the possibility of COVID vaccines being a contributing factor. The median age of infected children is two years old, which means that the vast majority of them are too young to be eligible for COVID vaccines.
Regardless, social distancing measures to contain COVID have been mentioned as a likely environmental factor contributing to an increasing rate of hepatitis infection. In the pre-COVID era, children could easily establish immunity to adenoviruses through face-to-face contact with peers. Yet with social distancing and online classes, they lose such opportunities and can become more vulnerable to adenoviruses. It seems that the COVID pandemic and our defense measures have more profound side effects yet to be explored.
Luckily, it is not all bad news out there. The UKHSA just reassured the public that the number of new cases has dropped significantly over the past two weeks. It is also highly unlikely that the hepatitis epidemic would ever develop into a pandemic like COVID.