Investigators are examining a possible relationship to adenovirus type 41 infection.
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In October 2021, five pediatric patients with hepatitis (inflammation of the liver) of unknown cause were identified in children at a hospital in Alabama. The children had significant liver illness, including some with liver failure, with no known cause.
The five children tested negative for hepatitis A, hepatitis B, and hepatitis C viruses and tested positive for adenovirus, a common virus that typically causes cold- or flu-like illness, or more rarely stomach or intestine problems. An additional review of hospital records later identified four additional patients, all of whom had hepatitis and adenovirus infection.
All of the children were previously healthy and ranged in age from one to six years old at the time of hospitalization. The children were from different parts of the state. No known contact or common exposures were found among the children. None of the children had significant underlying medical conditions.
In addition to looking for more cases in Alabama, the CDC issued a notice calling for state and local health departments nationwide to report potential cases. CDC is working with states to support them when patients under investigation are reported and is updating investigation numbers regularly.
Laboratory tests identified that some of the children in Alabama had adenovirus type 41, which is more likely to cause severe stomach illness in children. Although there have been previous reports of hepatitis in children with suppressed immune systems who were infected with adenovirus, adenovirus type 41 is not a common cause of hepatitis in otherwise healthy children.
Other common causes of viral hepatitis, such as infection with hepatitis A, B, C, D, and E viruses were considered, but evidence for these infections were not found in any of the patients. Some other causes have been ruled out for the children in Alabama, including: the virus that causes COVID-19, bacteria, autoimmune hepatitis and Wilson disease.
CDC is also aware of an increase in pediatric patients with hepatitis of unknown cause recently reported in other countries, and CDC is working with public health officials around the world to understand what they are learning. Adenovirus has been detected in some of these patients throughout the United Kingdom and Europe, but not among all of them. Investigators are considering other possible causes and identifying other possible contributing factors.
"At this time, the cause of the reported illnesses in these children is still unknown. While adenovirus has been detected in some children, we do not know if it is the cause of the illness," the CDC said. "We do not know and are investigating what role other factors play in this illness, such exposure to toxins or other infections that the children might have."
Cases of hepatitis in children over the past few years appear stable and are small numbers overall. CDC continues to look at data to understand the expected numbers of children with hepatitis. It is not unusual for the cause of some hepatitis cases in children to remain unknown; some estimates suggest 30-50% of hepatitis cases in children are from unknown causes. CDC is looking at overall trends in hepatitis in children.
The WHO is also monitoring reports of unexplained hepatitis in children around the world, according to WHO chief Tedros Ghebreyesus. "More than 700 probable cases of hepatitis of unknown cause in children have now been reported to WHO from 34 countries, and a further 112 cases are under investigation," said Ghebreyesus. “At least 38 of these children have needed liver transplants, and 10 have died.”
“WHO receives reports of unexplained hepatitis in children every year, but a few countries have indicated that the rates they are seeing are above what is expected,” said Ghebreyesus. He said the UN agency is working with countries to investigate the cause, but the five viruses that commonly cause hepatitis have not been detected in any of these cases. ■