Matthew R Vogt on link between acute flaccid myelitis & current acute paediatric hepatitis outbreak

More than 600 probable cases of acute hepatitis of unknown cause in children have been reported from 33 countries across the world from April 5-May 26, 2022, the World Health Organisation (WHO) noted.

Lab tests ruled out hepatitis A-E. However, several hypotheses are doing the rounds — the most popular one associating it with an adenovirus infection. 

An adenovirus infection is common in young children, typically resulting in “mild, self-limiting gastrointestinal or respiratory infections”. 

This medical mystery is reminiscent of when acute flaccid myelitis (AFM), a polio-like condition in children, was beginning to be understood a decade ago. 

The knowledge gap of what was causing AFM was finally closed last month when a paper, published in the New England Journal of Medicine on 26 May, detailed the case of an eight-year-old who died in 2008 of the condition. 

The term didn't really come into use until 2014, which was the first time an AFM outbreak was recorded in the United States. The study looked at the autopsy tissues, which were well preserved, and found evidence of the virus in the child's motor neurons. 

Down To Earth spoke with the paper’s lead author, Matthew R Vogt, to understand what AFM is and if there are any similarities with the ongoing paediatric hepatitis outbreak. 

Taran Deol (TD): What is AFM and what was the medical mystery around?

Matthew R Vogt (MV): AFM is a disease that typically happens to children. What usually starts as just a cold and fever, suddenly turns into severe weakness. Here, acute means sudden, flaccid means weakness and myelitis indicates the origin of this is in the spinal cord. Essentially, the motor neurons stop functioning. 

It's a highly variable disease. In the worst case, you could have every muscle in your body paralysed. But it can also be very subtle. 

An example of this is the case of a talented pianist who needed very high dexterity and good use of their arms but suddenly weren't able to play the way they used to. 

Experts were not sure what was causing the large outbreaks of AFM, that was the mystery. We suspected enterovirus D68 — a member of the Picornaviridae family, an enterovirus — was behind it. It is typically a common cold virus. 

Except we'd been noticing, during these outbreaks, enterovirus D68 was commonly found in the respiratory tract, occasionally in the stool and only very rarely in the spinal fluid of the children. 

But we also know this virus is a very close cousin of the poliovirus, so we thought it was likely causing AFM. 

TD: Was this enterovirus always the leading theory behind AFM?

MV: This was definitely the leading theory. And, to be clear, this isn't the only virus that can cause AFM but it's the main one that causes the big outbreaks of AFM. 

Poliovirus can also cause AFM, but we call that poliomyelitis. Other enteroviruses can also cause AFM, such as the West Nile virus that belongs to a completely different family.

TD: What is the treatment for AFM?

MV: The treatment, hopefully, will be better understood now that we know for sure what is causing AFM. Currently, there's nothing specific. 

If the paralysis reaches a point where the patient is unable to swallow or breathe, then intubation and feeding tube is needed. 

Unfortunately, that's the mainstay of therapy, there aren’t really any antiviral medications. 

Typically, there is some recovery of strength in children who get this illness, but there is usually some lifelong limitation in their ability to use the affected limb. 

TD: Do you see any similarities between AFM and the current severe paediatric hepatitis outbreak?

MV: As AFM cases began increasing in US, we also noticed enterovirus D68 infections. While that didn't mean it was causing AFM, it was very suspicious. 

And that is what sounds very familiar to the hepatitis outbreak. Almost every time they check for adenovirus in the blood, they find it. That's very suspicious, and very likely contributing to the cause. 

Just like enterovirus, adenovirus is not a new virus and is very common. And yet, we've never made the association with it causing severe hepatitis. 

Correlation does not prove causation, and that was the way it was with enterovirus D68 and AFM. And I suspect we will have a day in the future where we will likely be able to say adenovirus 41 can cause really severe hepatitis, but it's a rare outcome. 

TD: It took nearly a decade to bridge the knowledge gap for what was causing AFM. Do you suspect a similar timeline for hepatitis?

MV: Hopefully, we can be quicker. It was difficult with AFM because you can't do a biopsy of the spinal cord given there’s a risk of paralysis. But with the liver, you can do a biopsy even in a child who doesn't need a transplant. 

And if the child's hepatitis is so severe that they need a transplant, we’ll have the whole liver to study. It'll be potentially easier to investigate paediatric hepatitis cases.

We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.

Down To Earth is a product of our commitment to make changes in the way we manage our environment, protect health and secure livelihoods and economic security for all. We believe strongly that we can and must do things differently. Our aim is to bring you news, perspectives and knowledge to prepare you to change the world. We believe information is a powerful driver for the new tomorrow.

© Copyright Down To Earth 2022. All rights reserved.