An outbreak of acute hepatitis - an inflammation of the liver - in children has killed at least four and required liver transplants in more than a dozen others across the globe, according to the World Health Organization (WHO).
While the cause is undetermined, investigators are studying a family of pathogens, called adenoviruses, that cause a range of illnesses including the common cold.
1. WHEN AND WHERE DID IT START?
Cases were first identified at an Alabama hospital in October 2021, when five children were admitted with liver damage from an unknown cause. Early this year, 10 cases were identified in Scotland.
As of Apr 21, 169 cases had been detected, the WHO said. Most of them - 114 - were in the United Kingdom, with cases also found in Spain, Israel, Denmark, Ireland, the Netherlands, Italy, Norway, France, Romania and Belgium.
The United States Centers for Disease Control and Prevention issued a nationwide health alert, and as of Apr 28, at least five more US states had confirmed or suspected cases.
On Apr 28, Japan’s health ministry said that it found two more probable cases, taking the nation’s tally to three.
Singapore’s health ministry on Apr 30 confirmed a case of acute hepatitis in a 10-month-old baby, while Indonesia said that three children died from the disease last month.
2. HOW SERIOUS IS IT?
The affected children were between one month old and 16 years old, with many aged 10 and under.
Of the 169 cases reported by the WHO, 17, or about 10 per cent, needed a liver transplant, and at least one death was reported.
One of the four infections under investigation in Wisconsin resulted in a death, which would be the first in the US linked to the illness if confirmed.
3. WHAT ARE THE COMMON SYMPTOMS?
Abdominal pain, diarrhoea and vomiting, followed by jaundice, which is marked by the skin or the whites of the eyes turning yellow.
Laboratory tests show signs of severe liver inflammation, with markedly high liver enzyme readings. Most of the children didn’t have a fever.
Other symptoms of hepatitis include fatigue, loss of appetite, dark urine, light-coloured stools and joint pain.
4. WHAT'S CAUSING IT?
A viral organism is likely because the cases are appearing in clusters, according to Tina Tan, a physician at Lurie Children’s Hospital in Chicago and a member of the Infectious Diseases Society of America. But experts are still largely in the dark about which virus it could be.
The WHO said that adenoviruses were detected in at least 74 of the children, or more than 40 per cent of cases. In 18 of those, a specific strain has been identified: F type 41.
The findings are perplexing, however, since adenoviruses normally resolve on their own and don’t cause the severity of disease seen in the children.
Some were also infected with the coronavirus that causes COVID-19, though the role of any of the viruses is not clear.
US officials have expressed doubt about any connection with COVID-19, saying that all the patients in the initial Alabama cluster tested negative at the hospital and had no history of previous infection.
The WHO report also noted that the “vast majority” of children affected had not received any vaccine for COVID-19, making hypotheses about possible side effects from the shots unlikely.
Common pathogens that cause acute viral hepatitis, including hepatitis viruses A, B, C, D and E, haven’t been found in any of the cases, according to the WHO.
No other risk factors have been identified, including links to international travel, the WHO said.
Additional testing for other infections, chemicals and toxins is under way in the affected countries, which have also initiated enhanced surveillance.
5. WHAT IS AN ADENOVIRUS?
They are common viruses that cause a range of illnesses, including cold-like symptoms, fever, sore throat, bronchitis, pneumonia and diarrhoea.
There are more than 50 types that can infect humans. While they most commonly cause respiratory symptoms, they can also lead to gastroenteritis, conjunctivitis and bladder infections.
Adenovirus type 41 typically causes diarrhoea, vomiting and fever, often accompanied by respiratory symptoms. It isn’t known to cause hepatitis in healthy children.
6. IS THIS A KNOWN DISEASE?
It is possible that the severe hepatitis is an existing, though rare, result of an adenovirus infection that is being detected more often now thanks to enhanced testing, the WHO said.
Adenovirus infections have been on the rise recently after falling to low levels during the COVID-19 pandemic, potentially making young children more susceptible.
The possible emergence of a novel adenovirus must also be investigated, the WHO said.