Paediatric acute hepatitis of unknown aetiology: a national investigation and adenoviraemia case-control study in the UK

Developing a syndromic surveillance tool to support the epidemiological investigation into paediatric acute hepatitis of unknown aetiology in England

BACKGROUND

During 2022, a new public health threat emerged when cases of paediatric acute hepatitis of unknown aetiology (HUA) were identified in children aged under 16 years old in the United Kingdom (UK). At the time, the epidemiology and extent of cases was based upon limited and non-standardised reporting from hospitals and liver units. We aimed to adapt existing real-time syndromic surveillance systems to support the epidemiological investigation of cases of HUA presenting to emergency departments (EDs) in England.

METHODS

Syndromic surveillance is generally based on the collection of patient symptoms or chief complaints, which are collected using automated routines in near real-time. Here, we used an existing ED syndromic surveillance system monitoring daily patient attendances across a network of approximately 150 EDs in England. Clinical diagnosis codes related to the potential symptoms associated with the HUA incident were selected and attendance data monitored retrospectively and prospectively during the incident.

RESULTS

From 2 April 2018 to 31 December 2021, there were small sporadic numbers of daily ED attendances for 'liver conditions' in children with no observed secular trends or seasonality across the 1 to 4 and 5 to 14 years age groups. The period 2 April to 29 July was compared across each year included in the analysis. Mean daily HUA attendances during 2018 to 2021 was 0.05 and 0.22 for 1 to 4 and 5 to 14 years respectively, however in 2022 there were 0.26 and 0.42 mean daily attendances. This represented an increase of 377% and 94% in the 1 to 4 and 5 to 14 years age groups, respectively. From June 2022, daily syndromic 'liver condition' attendances appeared to decrease and the rate of increase in cumulative attendances slowed.

CONCLUSIONS

We demonstrate how syndromic surveillance provided support to the HUA outbreak using an existing syndromic surveillance framework to develop new indicators based on the newly emerging clinical symptoms. The outputs from the syndromic tool matched clinical and epidemiological findings with respect to trends in other HUA-related data, including clinical and laboratory reports, over time. This work demonstrates the potential for syndromic surveillance supporting the epidemiological surveillance of hepatitis and providing a valuable tool for the real-time management of future unknown health threats.

Metagenomic and transcriptomic investigation of pediatric acute liver failure cases reveals a common pathway predominated by monocytes

In 2022, a cluster of severe childhood hepatitis was detected primarily in Europe and North America, leading to a global alert by the World Health Organization. An association with adeno-associated virus 2 (AAV2) in conjunction with human adenoviruses was found. Five percent of the cases progressed to acute liver failure, necessitating transplantation. The mechanism of disease that accounts for fulminant liver failure in these patients remains incompletely described. An upsurge was observed of in the five total cases of acute liver failure that presented to the Dutch national referral center for pediatric liver transplantation in the spring of 2022. An in-depth molecular analysis of the mechanism of pediatric acute liver failure was performed using targeted transcriptomics and metagenomics to identify any virus present in the cases, immune profile haplotypes, and differentially expressed gene groups. Explanted liver tissue and plasma samples (n = 15) were subjected to viral metagenomic and human transcriptomic profiling, targeting >600 inflammatory genes. Liver transcriptomic signatures of transplanted cases were compared with those of pediatric controls from a liver biobank (n = 6). AAV2, adenoviruses, and herpesviruses were detected in liver explant tissue and plasma samples of the cases. Epstein-Barr virus and varicella zoster virus infection with pathognomonic clinical symptomatology preceded liver failure in two respective cases. AAV2 was detected in one-third of control livers. Excessive activation of monocyte pathways was detected in liver explants from cases compared with controls. Remarkably, this signature was comparable for AAV2, adenoviruses, and/or herpesviruses-positive transplant cases. Our multi-omic findings suggest a common transcriptomic profile, with an upregulation of monocyte pathways in the presented transplanted cases, which had similar severe clinical outcomes. In the cohort presented, AAV2 was not exclusively associated with acute liver failure, suggesting that other processes may have contributed to a uniform cascade of irreversible pathology.

IMPORTANCE

Since the appearance of the cluster of pediatric hepatitis of unknown origin in 2022, several groups have reported an association of adenoviruses and AAV2 in a high number of cases in contrast to controls. The adenoviruses detected were heterogeneous in both species-adenovirus C and F-and sequences. The mechanisms of disease that accounts for fulminant liver failure, occurring in 5% of pediatric hepatitis cases, remain incompletely described. The current study adds to previous data by including pediatric acute liver failure cases during the upsurge, enabling the analyses of inflammation expression profiles in cases with different viruses in relation to pediatric controls. This led to the discovery of transcriptome upregulation of monocyte pathways in liver explants from the cases. This inflammatory transcriptomic signature was comparable for AAV2, adenoviruses, and/or herpesviruses-positive transplant cases.

Investigation of an outbreak of novel hepatitis of unknown aetiology in children and adolescents, Ireland, 2021 to 2023

An outbreak of severe acute hepatitis of unknown aetiology in children (HUAC) was reported by the United Kingdom (UK) in spring 2022. Within days, a corresponding increase was identified in Ireland. A multi-agency incident management team (IMT), led by the Health Protection Surveillance Centre (HPSC), established a national case definition, trawling questionnaire, testing protocol and communications plan. Between 1 October 2021 and 12 May 2023, 44 probable and three possible cases of HUAC were identified in Ireland with a median age of 3 years. Adeno-associated virus 2 (AAV2), detected in 18 of 31 probable cases, and SARS-CoV-2 antibodies in 22 of 37 of probable cases were the most common infectious agents, followed by human herpes virus 7 (18/33) and adenovirus (20/44). Immunological findings included the human leukocyte antigen (HLA) class II HLA-DRB1*04:01 allele in 17 of 32 cases. Autoantibodies were found in 15 of 40 patients. Our findings corroborate those of the UK, which suggested a link between HUAC and AAV2 and another virus, in children predisposed due to presence of a particular HLA class II type. Close collaboration with the UK, the European Centre for Disease Prevention and Control (ECDC) and World Health Organization (WHO) was invaluable in the investigation.

Acute hepatitis of unknown aetiology in children: evidence for and against causal relationships with SARS-CoV-2, HAdv and AAV2

BACKGROUND

The cause of acute paediatric hepatitis of unknown aetiology (2022) has not been established despite extensive investigation.

OBJECTIVE

To summarise the evidence for and against a causal role for human adenovirus (HAdv), adeno-associated virus 2 (AAV-2) and SARS-CoV-2 in outbreaks of paediatric hepatitis in 2022.

METHODS

We appraised and summarised relevant evidence for each of the Bradford Hill criteria for causality using quantitative (statistical modelling) and qualitative (narrative coherence) approaches. Each team member scored the evidence base for each criterion separately for HAdv, AAV-2 and SARS-CoV-2; differences were resolved by discussion. We additionally examined criteria of strength and temporality by examining the lagged association between SARS-CoV-2 positivity, respiratory HAdv positivity, positive faecal HAdv specimens and excess A&E attendances in 1-4 years for liver conditions in England.

RESULTS

Assessing criteria using the published literature and our modelling: for HAdv three Bradford Hill criteria (strength, consistency and temporality) were partially met; and five criteria (consistency, coherence, experimental manipulation, analogy and temporality) were minimally met. For AAV-2, the strength of association criterion was fully met, five criteria (consistency, temporality, specificity, biological gradient and plausibility) were partially met and three (coherence, analogy and experimental manipulation) were minimally met. For SARS-CoV-2, five criteria (strength of association, plausibility, temporality, coherence and analogy) were fully met; one (consistency) was partially met and three (specificity, biological gradient and experimental manipulation) were minimally met.

CONCLUSION

Based on the Bradford Hill criteria and modelling, HAdv alone is unlikely to be the cause of the recent increase in hepatitis in children. The causal link between SARS-CoV-2, and to a lesser degree AAV-2, appears substantially stronger but remains unproven. Hepatitis is a known complication of multisystem inflammatory syndrome in children following COVID-19, and SARS-CoV-2 has been linked to increased susceptibility to infection post-COVID-19, which may suggest complex causal pathways including a possible interaction with AAV-2 infection/reactivation in hosts that are genetically susceptible or sensitised to infection.

The pattern of childhood infections during and after the COVID-19 pandemic

The rates of most paediatric infectious diseases declined during the initial phase of the COVID-19 pandemic due to the implementation of non-pharmaceutical interventions. However, after the gradual release of these interventions, resurgences of infections occurred with notable variations in incidence, clinical manifestations, pathogen strains, and age distribution. This Review seeks to explore these changes and the rare clinical manifestations that were made evident during the resurgence of known childhood infections. The magnitude of resurgences was possibly caused by a profound population immunity debt to specific pathogens in combination with the coinciding reappearance of viral and bacterial infections, rather than novel pathogen variants, increased antimicrobial resistance, or altered childhood immune function. As the usual patterns of paediatric infectious diseases were disrupted during the COVID-19 pandemic, the consequences of a population immunity debt were unravelled, and new insights into pathogen transmissibility, disease pathogenesis, and rare clinical manifestations were revealed.

Severe acute hepatitis of unknown origin in children: Is it still a mystery? What role does adenovirus play?

On March 31, 2022, severe acute hepatitis of unknown origin was first reported from the Royal Glasgow Children's Hospital in Scotland. According to the criteria by WHO-ECDC, a probable case of unknown acute hepatitis in children is defined as a subject under 16 years of age, who tested negative for viral hepatitis and transaminases >500 U/L, starting from the 1st of October 2021. WHO invites Member States to participate in the global effort to collect anonymized clinical data on probable cases of severe acute hepatitis of unknown aetiology. As of May 26, 2021, 650 cases were already registered on the platform worldwide, of whom at least 38 cases have required liver transplants. Several hypotheses such as previous SARS-CoV-2 infection or coinfection or infection with another virus were examined and a strong association was found between adenovirus (41F) and acute hepatitis of unknown aetiology cases. This review article summarizes the global epidemiological evidences on acute hepatitis of unknown origin in children, analysing their incidence and characteristics.

Epidemiology of Adenovirus Infection in Hospitalized Children in the United States From 1997 to 2019

OBJECTIVE

The study aimed to explore the prevalence, clinical features, resource utilization, temporal trends and outcomes associated with adenoviral infections in hospitalized children.

METHODS

A retrospective analysis using the Healthcare Cost and Utilization Project's Kids' Inpatient Database from 1997 to 2019 was performed. Children 29 days to 17 years of age with adenoviral infection were selected. Chi-square, Kruskal-Wallis tests, linear trend analysis and multivariable analysis were used for data analysis.

RESULTS

A total of 40,135 children under 18 years of age with adenoviral infection were discharged in the United States with an overall prevalence of 18.9 per 10,000 discharges and 6.9 children per 100,000 population. By linear trend analysis, the hospitalization rate has significantly increased with the highest prevalence in 2019. Adenoviral infection was more prevalent in Black children, in winter months, in the Midwest region, in children with government insurance and in the lowest income quartile. The majority (85%) of adenovirus-related hospitalizations occurred under 6 years of age. Mechanical ventilation, extracorporeal membrane oxygenation support, acute kidney injury and liver failure were documented in 11.9%, 0.4%, 2.7% and 0.4%, respectively. The overall case fatality rate was 1.4%, which decreased from 1997 to 2019 ( P < 0.05). By regression analysis, an increased mortality rate was associated with the need for mechanical ventilation, the presence of complex chronic conditions, immune deficiency, central nervous system infection and pneumonia/bronchiolitis.

CONCLUSIONS

Most human adenovirus infections occur in children under 6 years of age and cause mild illness. Human adenovirus can lead to serious illness in children with complex chronic conditions and immune deficiency conditions.

Viruses in Wastewater-A Concern for Public Health and the Environment

Wastewater monitoring provides essential information about water quality and the degree of contamination. Monitoring these waters helps identify and manage risks to public health, prevent the spread of disease, and protect the environment. Standardizing the appropriate and most accurate methods for the isolation and identification of viruses in wastewater is necessary. This review aims to present the major classes of viruses in wastewater, as well as the methods of concentration, isolation, and identification of viruses in wastewater to assess public health risks and implement corrective measures to prevent and control viral infections. Last but not least, we propose to evaluate the current strategies in wastewater treatment as well as new alternative methods of water disinfection.