(WJW) – The Centers for Disease Control and Prevention released new information this week on its investigation into what is causing acute liver failure in children.

Five children have died in the outbreak that was first identified in the U.S. in the fall.

What’s new

The CDC is investigating whether the severe cases of hepatitis with an unknown cause are connected to an adenovirus type 41 infection.

Adenoviruses have a wide range of symptoms, including respiratory problems, fever, pneumonia and diarrhea.

Typically, that only occurs in people with weakened immune systems and is extremely mild in otherwise healthy people.

What we know

There are now 228 cases in 20 countries, according to the World Health Organization numbers from the beginning of May.

WHO reports 109 cases in the U.S. since October.

Five children have died.

In the cases affecting children, the kids were healthy, with no immune deficiencies and no underlying health problems.

The hepatitis origin is unknown. Health officials have ruled out hepatitis A through E.

Doctors can’t figure out why the children are developing hepatitis, which is an inflammation of the liver.

Most of the children are too young to have received a COVID-19 vaccine and there is no evidence of coronavirus.

Doctors have also ruled out bacteria, urinary tract infection, autoimmune hepatitis and Wilson disease.

There is no known link to geographic location, animals, food or travel. Many of the children are testing positive for adenovirus, but not all.        

The CDC is asking health departments across the U.S. to test kids who have liver inflammation for adenovirus.

Cases in Ohio

A doctor at Cincinnati Children’s Hospital told NBC News they’ve treated 6 cases of severe hepatitis in previously healthy children.

One required a liver transplant, which occurs in about 10 percent of all known cases.

The children at Cincinnati Children’s range in age from 18 months to 10-years-old.

FOX 8 has reached out to the hospital for more details on the cases and the timeline of the cases.

Here’s what they told us:

“As a referral center, Cincinnati Children’s sees similar cases throughout the year, and are on the lookout for any children with evidence of liver injury to make sure they are evaluated promptly and receive the care they need to recover without problems.”

Cincinatti Children’s Hospital Public Relations

FOX 8 has also contacted the Ohio Department of Health to learn more about how many children they’ve seen in the state.

ODH has not returned our calls.

First U.S. cases

The first known cases in the U.S. were in Alabama.

In October, nine children who had no link to each other were treated for acute liver failure.

The children were healthy but developed symptoms of gastrointestinal illness and varying degrees of liver injury and liver failure.

According to the CDC, all of the children are in recovery, including the kids who required liver transplants.

What we don’t know

Investigators don’t know the cause.

Because adenovirus isn’t present in all cases, it’s not clear that it is causing the illness.

The CDC is also looking into exposure to toxins or other possible infections.

The CDC says it’s not clear how many hepatitis cases there are in children right now.

What to look for

The CDC wants parents to watch for symptoms in their children.

Health officials say the children have a jaundice-type look, with a yellow color to the skin and the white part of the eyes.

Other symptoms include dark urine and white stool.