A further 20 cases of hepatitis have been confirmed in children aged 10 and under, according to the UK Health Security Agency.
It brings the total number of cases in the UK to 222, as of 25 May.
Of those cases, 158 are in England, 31 in Scotland, 17 in Wales and 16 in Northern Ireland.
Dr Renu Bindra, senior medical adviser and incident director at UKHSA, said: “Our investigations continue to suggest an association with adenovirus, and we are exploring this link, along with other possible contributing factors including prior infections such as COVID-19.
“We are working with other countries who are also seeing new cases to share information and learn more about these infections.
“The likelihood of children developing hepatitis remains extremely low.
“Maintaining normal hygiene measures, including making sure children regularly wash their hands properly, helps to reduce the spread of many common infections, including adenovirus.
“We continue to remind everyone to be alert to the signs of hepatitis – particularly jaundice, look for a yellow tinge in the whites of the eyes – and contact your doctor if you are concerned.”
In recent weeks, several countries have seen a surge in hepatitis cases, with the European Centre for Disease Prevention and Control stating that around 190 unexplained cases of severe hepatitis have been reported in children around the world, with some 40 cases recorded in the European Union and European Economic Area.
The outbreak has also reached Asia, after the first case was reported in Japan on 21 April.
Hepatitis is the term used to describe inflammation of the liver and is usually the result of a viral infection.
On 12 May, it was reported that a child died from the disease at a hospital in the Republic of Ireland, while another child, who was also being treated for the illness, received a liver transplant in the UK.
Severe hepatitis is rare in otherwise healthy children.