https://www.cdc.gov/mmwr/volumes/71/wr/mm7118e1.htm
There's been a global outbreak of hepatitis of unknown etiology in children in recent months. There's been nearly 200 cases globally with 17 requiring liver transplants and 1 death. The cause is not known at this time.
One hypothesis is it is from an adenovirus infection, or a co-infection with an adenovirus as many of the children are testing positive for adenovirus. 9 children in Alabama were identified from October to February with adenovirus infection and acute hepatitis. Like in some other cases, of the adenovirus infections that could be sequenced, all 5 were adenovirus type 41.
Besides adenovirus testing, they were screened for several other pathogens. 6 out of the 9 also tested positive for EBV, but these were likely reactivation of previous infections. 4 out of 8 were positive for enterovirus. All were negative for Hep A/B/C. None were positive for the coronavirus, and none of them had any documented history of a previous coronavirus infection.
2 of the 9 required liver transplants. All 9 recovered.
Acute hepatitis from an adenovirus infection is possible, but rare. It is seen in immunocompromised children. However all these children were immunocompetent.
Too early to say what is the cause of this outbreak. The one thing that can be ruled out with certainty is that it wasn't caused by the coronavirus vaccine. None of the cases have occurred in children that have received the coronavirus vaccine.