Seven more cases of severe hepatitis have been detected in California, and a child has died in Wisconsin, as the mysterious disease spreads throughout the country.
California's Department of Health said it had detected the cases in 'young' children, who had all been taken ill since October.
It takes the U.S. total for suspected hepatitis cases to 27, with the condition now being spotted across seven states — mostly east of the Mississippi river.
Wisconsin is the only state to report a suspected child death from hepatitis. If confirmed, it will be the first in the country and second in the world. State officials confirmed to the DailyMail.com that the child had developed the disease after being infected with the adenovirus.
Cases of the peculiar illness have already been spotted in Alabama, North Carolina and Delaware. Health chiefs in Illinois and New York are currently probing reports of similar occurrences.
The cause of the mysterious illness remains a 'mystery', chief medical adviser to President Joe Biden, Dr Anthony Fauci says.
But experts have raised concerns that lockdowns weakening immunity in children s or even Covid infections could be to blame.
Experts say lockdowns may have weakened the immunity of children and left them more susceptible to the virus, or it may be a mutated version.
Nearly 200 children have been sickened by the condition across the world in up to 14 countries. At least 18 have needed liver transplants.
Nearly 200 children have been sickened by the condition across the world in up to 14 countries since last October *cases in Canada, Japan and Wisconsin, Illinois and New York are still yet to be confirmed
Dr Anthony Fauci, chief medical advisor to President Joe Biden, said the cause of the illness is 'still a mystery'
The California department of health said it was unclear whether adenovirus — which typically causes colds — was behind the illnesses, or if the cases were connected.
Medics have been left puzzled by what is behind the spate of cases — with the usual hepatitis A, B, C, D and E viruses excluded from laboratory test results.
Health chiefs believe the illness may be triggered by an adenovirus, which usually causes common colds.
Dr Fauci told Bloomberg: 'It’s still a mystery. It seems to be associated with adenovirus, but it isn’t a slam dunk.'
Alabama was the first state to announce cases of the severe liver injury two weeks ago.
Nine children were hospitalized in the state between November and February.
Three had acute liver failure and all of the children tested came back positive for adenovirus.
Two required liver transplants but all of them survived.
North Carolina identified two cases last month, with both children recovering. Neither had adenovirus.
Delaware this week reported that a child younger than five was hospitalized by the same mysterious hepatitis. They are still undergoing treatment.
One child has now been confirmed dead in Wisconsin, with officials revealing they are investigating whether their liver injury was linked to the same cluster of cases.
The Wisconsin DHS said: 'Since being notified of this adenovirus-associated hepatitis cluster, DHS is now investigating at least four similar cases among children in Wisconsin.
'This includes two children who had severe outcomes, one liver transplant, and one fatality.'
Both the child that died and the one that required a live transplant are confirmed to have been infected with adenovirus.
Illinois officials said they had spotted three probable cases of severe hepatitis on Monday and one child required a liver transplant.
Dr Tina Tan, pediatric infectious disease physician at Lurie Children’s Hospital in
