HOUSTON, TEXAS - AUGUST 23: Children participate in an activity in class at the Xavier Academy on August 23, 2021 in Houston, Texas. In-person classroom sessions are resuming and schools around Houston are requiring mask mandates, keeping in accordance with CDC guidelines. Harris County Judge Lina Hidalgo has gone against Gov. Greg Abbott's statewide ban on mask mandates and has issued an order that requires face coverings to be worn in schools. All staff and faculty at Xavier Academy have been vaccinated and 90% of students in attendance have also been vaccinated. (Photo by Brandon Bell/Getty Images)

NEW YORK (AP) — Health officials remain perplexed by mysterious cases of severe liver damage in hundreds of young children around the world. The best available evidence points to a fairly common stomach bug. That virus hasn’t previously caused this kind of problem in otherwise healthy kids. Investigators in the U.S. and abroad are exploring a number of theories that might explain the mystery. One possibility that’s not yet proven: that the stomach virus and the coronavirus are combining to provoke a liver-damaging immune system response.