At least one child has died from an increase in hepatitis, according to the World Health Organization (WHO).
There are now 169 reported cases of unknown origin in 12 countries – including the United Kingdom, the United States, Spain, Israel and Ireland – among young people aged one month to 16 years.
The United Kingdom reported 114 cases.
The WHO did not provide any details about the death and did not say where it occurred.
One possible line of research is whether a group of viruses called adenoviruses can cause disease.
The common cold virus, known as adenovirus, has been detected in at least 74 cases. COVID-19 infection was identified in 20 cases and 19 cases had both viruses. There is no link to coronavirus attacks, officials in the United Kingdom said.
The latest figures come at a time when health authorities around the world are investigating a mysterious increase in severe cases of hepatitis, an inflammation of the liver in young children.
“Mild hepatitis is very common in children after a number of viral infections, but what is currently being observed is quite different,” said Graham Cooke, a professor of infectious diseases at Imperial College London, earlier this week.
A girl who had only hours left to live, as rare cases occur in children
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3:46 A girl who has only hours left to live
Some of the cases in the United Kingdom required specialized care in liver units, and at least six patients needed a liver transplant.
In Britain, parents are encouraged to notice the symptoms of the disease, which in some cases can cause scarring of the liver or loss of liver function.
Symptoms of hepatitis include jaundice (yellowing of the eyes and skin), dark urine, itchy skin, muscle and joint pain, loss of appetite, and fever.
U.S. health officials have issued a nationwide warning to warn doctors to look out for signs of childhood hepatitis.