The U.S. has reported 355 probable cases of acute hepatitis of unknown origin among children in 42 states and jurisdictions as of July 20, according to the CDC.
The latest tally is up from 338 cases reported July 13. Globally, more than 1,000 cases have been identified in 35 countries, according to the World Health Organization.
Researchers are still investigating the cause of the illnesses. Two studies published July 13 in The New England Journal of Medicine offer circumstantial evidence that adenovirus 41 may be responsible — or a contributing factor — to the illnesses, according to The New York Times.