A further 20 cases of hepatitis have been confirmed in children aged 10 and under, the UK Health Security Agency (UKHSA) has said.
It brings the number of cases of the liver disease hepatitis among children under the age of 10 that have been detected to more than 220, health officials have confirmed.
Of the confirmed cases of sudden onset hepatitis, 158 are resident in England, 31 are in Scotland, 17 are in Wales and 16 are in Northern Ireland, the UKHSA said.
An investigation is underway into the rise in cases of sudden onset hepatitis, also known as liver inflammation.
The UK Health Security Agency (UKHSA) said that it, Public Health Scotland, Public Health Wales and the Northern Ireland Public Health Agency were continuing to examine the cases, which have all occurred since January.
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As more children catch hepatitis, what are the signs to watch out for?
What is hepatitis?
Hepatitis is a broad term which describes an inflammation of the liver.
It is usually caused by a virus, though it can also occur due to liver damage from drinking alcohol, according to the NHS.
There a five types of hepatitis caused by viruses, known as A, B, C, D and E, but none of the cases in seen in children this time seem to have been caused by these.
What are the symptoms of hepatitis?
pale, grey-coloured poo
yellowing of the eyes and skin (jaundice)
muscle and joint pain
a high temperature
feeling and being sick
feeling unusually tired all the time
loss of appetite
What could have caused these cases?
The cause of the new cases is unknown so far.
The cases have not been caused by the usual viruses that cause hepatitis A – E and data gathered has “increasingly” suggested that the rise in severe cases of hepatitis may be linked to a group of viruses called adenoviruses, the agency said.
Adenoviruses are a group of viruses that are common causes of illnesses such as colds, vomiting and diarrhoea.
Of 53 cases tested earlier this year, 40 (75%) showed that adenovirus was the most common pathogen detected.
A total of 16% of cases, meanwhile, were positive for Covid-19, which was not unexpected due to the high rates of the virus during January to April this year.
The UKHSA stressed there is "no link" to the Covid vaccine. None of the currently confirmed cases had been vaccinated, it said.
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Experts have also ruled out a link with dogs.
Calum Semple, professor of child health and outbreak medicine at the University of Liverpool, told a briefing in May that investigations had found no role for either owning dogs or recent contact with dogs in cases of acute hepatitis.
The UK Health Security Agency (UKHSA) noted previously that around 70% of a sample of affected children had had recent contact with dogs or owned dogs.
Have cases been found in any other countries?
Cases have been identified in Denmark, Ireland, the Netherlands and Spain, the European Centre for Disease Prevention and Control said, while nine infections have been found in Alabama in children aged between one and six, according to US officials.
What should parents do?
Public health officials have advised people to practice good hand and respiratory hygiene, and parents have been reminded to supervise thorough hand washing in younger children, to reduce the risk of transmitting adenovirus.
Parents and carers should be alert to the signs of hepatitis including jaundice - skin with a yellow tinge which is most easily seen in the whites of the eyes.
If a child develops any symptoms they should be kept away from school, and parents should seek advice from a GP.