A mysterious liver disease infecting kids across Europe and the US has now killed at least 1 child

• A mysterious hepatitis spreading across Europe and the US has killed at least one child, the WHO reported.
• Health experts aren't exactly sure what's causing the liver-inflammation cases yet, but they think an adenovirus may be at work.

The mysterious outbreak of hepatitis spreading across Europe and the US has killed at least one child.

On Saturday, the World Health Organization announced that "at least one death has been reported," among the 169 hepatitis cases the agency has identified since early April.

So far, this liver-inflaming condition has hit at least 11 European countries and two US states. The Centers for Disease Control and Prevention told Insider in an email that this first recorded death was not a US case, but said the agency has recieved "additional reports" of cases from other US jurisdictions since its advisory went out late last week, and it is evaluating them.

It's still unclear exactly what's causing this hepatitis, but disease detectives worldwide suspect that a virus called adenovirus 41 may be the trigger for this liver inflammation in children. At least 17 of the patients, who've ranged in age from 1 month to 16 years old, have required liver transplants so far.

The outbreak is bizarre because hepatitis caused by adenovirus 41 doesn't usually infect healthy, young children. The WHO said adenovirus infection is a "possible hypothesis" for these hepatitis cases, but that "investigations are ongoing for the causative agent." Adenovirus has been identified in at least 74 of the cases, and at least 19 of the kids were co-infected with the coronavirus and adenovirus, the WHO said.

So far, in addition to the 11 US cases, more than 150 cases have been reported in Europe, including:

• 114 in the United Kingdom
• 13 in Spain
• 12 in Israel
• 6 in Denmark
• less than 5 in Ireland
• 4 in the Netherlands
• 4 in Italy
• 2 in Norway
• 2 in France
• 1 in Romania
• and 1 in Belgium.

The UK, where the majority of the cases have been reported so far, has recently seen an uptick in adenovirus infections in the community, and so has the Netherlands.

Common symptoms of this issue include abdominal pain, diarrhea, and vomiting. Adenovirus 41 spreads — like COVID-19 does — through close contact.