Please refer to the attached file.
This technical note is in follow-up to the communication published by the World Health Organization (WHO) on 23 April 2022 and updated on 25 April 2022 on the Event Information Site for the International Health Regulations (IHR) National Focal Points (EIS) and the information published in the Disease Outbreak News website on 23 April 2022.
On 5 April 2022, the first report was received from the United Kingdom (UK) reporting an increase in cases of acute hepatitis of unknown origin in previously healthy children under 10 years of age, all residents of Scotland. A week later, additional cases under investigation were reported from England, Wales, and Northern Ireland.
To date, a total of 169 cases of acute, severe hepatitis of unknown origin have been reported among children aged 1 month to 16 years in 12 countries, including one death. Of the 169 cases reported, 85 cases were tested for adenovirus, of which 74 were positive. Adenovirus type 41 was identified in 18 cases.
Most of the reported cases were classified considering the current working case definition, which are based on the clinical-epidemiological characterization of the cases identified to date.
Clinical manifestations among identified cases correspond to acute hepatitis with elevated transaminases, many presenting with jaundice and gastrointestinal symptoms (including abdominal pain, diarrhea, and vomiting) and none presenting with fever. Infections caused by hepatitis A, B, C, D, and E viruses were not identified among any of the affected children. Clinical outcomes thus far have varied, with 10% requiring liver transplantation.
On 18 April 2022, the United States of America IHR National Focal Point (NFP) reported a total of 9 cases of acute hepatitis among children aged 1 to 6 years to the Pan American Health Organization/World Health Organization (PAHO/WHO); the cases were identified between 2 October 2021 and 21 February 2022. Among the 9 cases, 7 were female, and all 9 cases presented with signs and symptoms compatible with different stages of hepatitis (scleral jaundice, jaundice, hepatomegaly, encephalopathy, and elevated transaminases). Two children required liver transplantation, whereas the rest of the cases were managed clinically. Adenovirus type 41 was identified in whole blood samples by RT-PCR in 5 of the 9 cases. A possible association between cases of severe acute hepatitis in the pediatric population and adenovirus infection is currently being investigated.