Worldwide, the number of mysterious hepatitis cases under investigation among children has reached 450, the European Center for Disease Prevention and Control said this week.
That’s more than double the number the group reported two weeks ago, and significantly higher than the World Health Organization’s latest count of 348.
Cases of this liver inflammation have been reported in more than 25 countries, though the majority are in the UK (around 160) and the U.S. (around 110). Most of the affected children are under age 5. Of the U.S. patients, more than 90 percent have been hospitalized and 14 percent have had liver transplants. The Centers for Disease Control and Prevention is investigating five pediatric deaths that might be related.
Disease experts aren’t sure what’s behind these cases, though several hypotheses have begun to emerge. The leading theory is an adenovirus, which often causes cold- or flu-like symptoms or stomach problems.