No patient tested positive for adenovirus DNA in plasma; however, only four of them had a plasma sample for adenovirus taken at onset of symptoms. On 5 April 2022, the United Kingdom Health Security Agency (UKSHA) first reported an increase in number of paediatric patients with severe acute hepatitis of unknown aetiology during the first 3 months of the year compared with previous years. Acute hepatitis of unknown origin - What we know so far.