Researchers are investigating a possible connection between children infected with hepatitis and adenoviruses and liver damage in children.
The Centers for Disease Control and Prevention advised physicians and public health officials Thursday to be on the lookout for pediatric patients with hepatitis from unknown causes.
Similar to cases in the U.S., there have been no child deaths, but six did require liver transplants.
"Overall, the [etiology] of the current hepatitis cases is still considered unknown and remains under active investigation," a WHO news release said.
"Laboratory testing for additional infections, chemicals and toxins is underway for the identified cases."