Technical Note: Acute, severe hepatitis of unknown origin in children. 29 April 2022.

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 20221.

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.

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