The Centers for Disease Control and Prevention announced Thursday that the public health agency is looking into a cluster of hepatitis cases among children.

According to a press release, the federal agency is studying nine hepatitis cases in Alabama "of unknown origin in children ranging in age from 1 to 6 years old, all of whom were previously healthy." The children have also tested positive for adenovirus infection, which most commonly causes respiratory illness, but depending on the type, can cause gastrointestinal infection in children.

How significant is this national health alert?

The rise in hepatitis cases in the U.S. mirrors an increase in cases among youths in the U.K., which started seeing more kids with hepatitis in January, according to the Associated Press.

"It falls under the category of the fact that the CDC is actively engaged in non-COVID surveillance and this is a perfect example of that," ABC News' chief medical correspondent Dr. Jen Ashton told "Good Morning America."

"Hepatitis -- that umbrella term for inflammation of the liver -- can be caused by viruses but it can also be caused by toxins, medications. [It's] very unusual to see it in this pediatric population," Ashton added.

Should parents be concerned?

Parents should be aware that there are cases where children are getting sick and if they notice symptoms or suspect a case of hepatitis or liver inflammation, they should consult their child's pediatrician immediately.

"At this point, this is rare. It's just something CDC is keeping an eye on," Ashton said.

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What causes hepatitis?

Hepatitis viruses are the most common cause of hepatitis in the world, including hepatitis A, B, and C, but they've been ruled out in the Alabama cluster. Researchers at the CDC suspect that the adenovirus infections may have caused the pediatric hepatitis cases and are still working to find out more information.

What are the symptoms of hepatitis?

Hepatitis symptoms include jaundice or yellowing of the skin and eyes, abdominal pain, nausea, or vomiting, dark-colored urine, or pale bowel movements.

What can parents do?

The CDC recommends that children receive vaccinations for hepatitis A and B. There is currently no vaccine available for hepatitis C.