There have been 169 cases recorded globally and one death, with 114 children diagnosed falling ill in the UK, and 10 needing a liver transplant.
The UK Health Security Agency (UKHSA) has now said that a strain of adenovirus called F41 is looking like the most probable cause.
But what is adenovirus?
Here’s what you need to know.
What is adenovirus?
Adenoviruses are common viruses that cause a range of illnesses and symptoms, including cold-like symptoms, fever, sore throat, bronchitis, pneumonia, diarrhoea, and conjunctivitis.
You can get an adenovirus infection at any age.
Adenoviruses are usually spread from infected people to others through:
- close personal contact such as touching or shaking hands
- the air by coughing and sneezing
- touching objects or surfaces with adenoviruses on them then touching your mouth, nose, or eyes
Is adenovirus linked to rare cases of hepatitis?
Adenovirus is being explored as a possible link to the rare cases of hepatitis recently identified in some children across the globe.
Most of the children affected are five years old or younger and have had symptoms of gastroenteritis illness, including diarrhoea and nausea, followed by jaundice or yellowing of the skin and eyes, which is a sign that the liver is struggling.
Dr Meera Chand, director of clinical and emerging infections at UKHSA, said: "Information gathered through our investigations increasingly suggests that this rise in sudden onset hepatitis in children is linked to adenovirus infection.
"However, we are thoroughly investigating other potential causes."
Experts have stressed that most children who catch adenovirus will not become very unwell.
Hepatitis symptoms include:
- dark urine
- pale, grey-coloured poo
- itchy skin
- 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
- tummy pain
The symptoms of the disease may first look like symptoms of other health problems.
If you are concerned about your child, you should seek advice from your GP.
One of the possible explanations being explored behind the sudden cases of hepatitis in children is that restrictions imposed in the pandemic may have led to young children being first exposed to adenovirus at a slightly later point in their lives.
Professor Calum Semple, an expert in infectious diseases at Liverpool University, told the BBC: "Adenovirus virtually disappeared during the Covid outbreak when there was reduced mixing and it has come back in a surge now."