In this blog post, Dr Kimberly Marsh, Consultant Healthcare Scientist and Dr Kirsty Roy, Consultant in Health Protection at Public Health Scotland, and co-authors of a recently published Eurosurveillance paper on the current investigation into severe hepatitis in children, explains how the first cases were identified and what public health actions were taken next in response.

It’s an unnerving time for families and friends—and the public—when young children become unwell without a known cause.

On 6 April, Public Health Scotland (PHS) reported on just such a situation, with a cluster of 11 children, mostly between the ages of 3 and 5 years old, presenting in hospital with jaundice and severe hepatitis. Hepatitis is a condition that affects the liver and usually is caused by one of several viral infections common in children. However, in this incident, a cause was not known.

Since then, public health agencies across the UK have reported on a similar upsurge. Severe hepatitis among children of unknown cause also have been reported in 11 countries around the world, although some background cases are to be expected.

Many people have asked whether this severe disease affected children in Scotland first or whether clinicians working in Scotland noticed it first. As evidence comes in from across the world, it is now clear that while Scotland was the first to detect and report such a cluster; cases were occurring elsewhere at similar points of time. So why was this cluster of children with severe hepatitis noticed in Scotland first?

Detecting and confirming a signal

Clusters such as the surge in hepatitis cases are typically identified by perceptive clinicians. In this case, it was a small group of paediatric consultants working at three of Scotland’s largest children’s hospitals who first noticed the unusual cluster. Typically in Scotland, these doctors might see 4 to 8 cases of children presenting with unexplained jaundice in a year, whereas in the month of March alone they had seen nearly as many. With this benchmark in mind, they immediately reported the cluster to their local NHS Board who in turn reported it to PHS.

This simple act of reporting is what triggers public health action. Following their report, PHS and NHS Board scientists immediately formed a problem assessment group and initiated a response to validate the signal and to learn whether other countries might also be seeing this signal. One of the ways that we validated this signal is by looking at routine surveillance and hospital data over the last couple of years. Epidemiologists and statisticians call these types of investigations “Exceedance analyses.” In the case of the hepatitis cluster, this analysis confirmed an unusual pattern of hepatitis and jaundice among children ages 0 to 4 years.

Investigating to identify a cause

Investigations to identify a cause are occurring at an urgent pace as the number of cases in the UK continue to slowly rise. This means that every day since the initial PHS report went out, epidemiologists, clinicians, laboratorians and data analysts across the UK have all been working together to create a full picture of our understanding.

Our approach is founded on tried and tested outbreak investigation methods, the objective of which is to identify a cause and prevent further disease.

Steps to carrying out an outbreak investigation include:

1. Agree on a case definition
2. Identify common exposures or experiences
3. Suggest a set of potential causes
4. Test to include or exclude causes
5. Take public health action based on what we learn

In the case of the hepatitis outbreak, the UK Health Security Agency (UKHSA) has recently published a technical briefing on the current status of the investigation, which includes information about the cases in Scotland. The briefing highlights findings from the above steps and, in particular, suggests that one of the leading potential causes of the severe disease is adenovirus. Adenoviruses are a family of common viruses that cause a range of symptoms, including colds, vomiting and diarrhoea. While they don’t typically cause hepatitis, it is a known rare complication.

Assessing the risk and advising parents and caregivers

Although adenovirus is a reasonably common virus among children in Scotland presently, the current risk to children of severe hepatitis is low. Thus far, only a very small number of children have been admitted to hospital in Scotland and this number is increasing only slowly over time. If most of the cases of hepatitis requiring hospitalisation are due to a common adenovirus (perhaps in combination with other factors), then it suggests the nearly all children are recovering from their infection without concern. Regardless, we’re working hard to definitively identify the cause so that we can determine how common the problem is.

This being said, the illness among the children that ultimately required hospitalisation has been severe. Even without knowing a cause, specific treatments are being assessed to see if they can reduce the severity of that disease. And although the outbreak investigation continues and a cause is not yet known, it doesn’t mean that public health action to prevent disease in the first place can’t be undertaken. In almost all infectious conditions, viruses are commonly passed from person to person and by touching contaminated surfaces. We continue to recommend to parents and caregivers that they adopt thorough handwashing (including supervising children) and good respiratory hygiene (such as covering the mouth and nose while coughing or sneezing, and using tissues then throwing them away).

In addition, parents and caregivers should be alert to the signs of hepatitis (including jaundice) and contact a healthcare professional if they are concerned.

Last updated: 13 June 2022