Parents in the UK are being warned to check their children for signs of hepatitis after more than 70 youngsters aged under 10 were diagnosed with the illness.
Jaundice, dark urine, itchy skin, muscle and joint pain, loss of appetite and a high temperature are among the symptoms of the inflammatory liver condition.
Around 60 cases have been found in children in England and 11 cases in Scotland saw children sent to hospital.
Dr Meera Chand, director of clinical and emerging infections at the UK Health Security Agency, said “investigations for a wide range of potential causes are under way, including any possible links to infectious diseases.
The aim, she said, is to raise awareness among healthcare professionals so any other cases in children “can be identified early and the appropriate tests carried out.”
Parents, Dr Chand said, should recognise the symptoms of jaundice, including “skin with a yellow tinge which is most easily seen in the whites of the eyes – and to contact a healthcare professional if they have concerns.”
While the condition may have occurred for a number of reasons, including several viral infections common in children, the cases under investigation have not found the common viruses which usually cause the condition.
Health managers in Scotland admitted the speed it has moved, the severity of cases and geographical spread made the outbreak “unusual”.
Cases have been diagnosed across the country in Lanarkshire, Tayside, Greater Glasgow and Clyde and Fife.
There are currently no clear causes and no obvious connection between them, Public Health Scotland (PHS) said.
Dr Nicholas Phin, PHS director of public health, said their investigation was in its early stages.
He said: “If you have a child who is showing signs of jaundice, where the skin has a yellow tinge, and is most easily seen in the whites of the eyes, then parents should contact their GP or other healthcare professional.
“We are continuing to investigate these cases and will provide further updates as and when they are available.”