Public health officials are keeping a close eye on an outbreak of hepatitis affecting young children in the United States and Europe.

The outbreak involves 11 countries so far and public health officials are at a loss to explain it. According to the World Health Organization, 169 cases of acute hepatitis have been reported so far, with no known link. It affects children between the ages of one month and 16 years old.

Hepatitis, in general, is liver inflammation, according to Dr. Jean Molleston, a pediatric gastroenterology expert with Riley Children’s Health. Viral hepatitis is typically caused by one of several viruses.

However, the typical viruses associated with hepatitis have not been found in the current cluster of cases.

“In the United States, as well as in other countries, there has been an unusually large number of cases of children with hepatitis,” Molleston said. “You may normally see a rare case in countries like the UK, but various cities in the United States have reported more cases than you would normally see.”

In many cases, hepatitis is mild. It can, however, require hospitalization and result in liver failure in severe cases. Typical symptoms include abdominal pain, diarrhea, vomiting, jaundice and increased levels of liver enzymes.

Seventeen children have needed liver transplants, representing about 10% of reported cases from the current outbreak. One death has been reported so far. The cause remains elusive, though adenovirus has been detected in 74 of the cases, according to WHO.

“Because viruses are a common cause of inflammation of the liver, the first thought was looking for normal hepatitis viruses, like hepatitis A and much less commonly B or C, monoviruses or other viruses,” Molleston said. “More recently, there have been queries as to whether a virus called adenovirus could play a role.”

Adenoviruses are common and often cause respiratory issues, according to Dr. John C. Christenson, a pediatric infectious disease specialist with Riley. Occasionally, adenovirus can cause other symptoms, including liver inflammation, in immunocompromised or seriously ill children.

It is not often associated with hepatitis.

“Adenovirus is traditionally not a virus that likes to cause hepatitis in normal children, which is overwhelmingly this population that is being described around the world,” Christenson said of the current outbreak.

“The few patients where adenovirus has been found, it’s a strain that we, Dr. Molleston and I, have seen for many years that is notorious for causing diarrhea,” Christenson said. “But this particular strain now, it’s being reported, is causing hepatitis. We’re not sure exactly if there is a relationship there. More investigation needs to happen before we can absolutely say adenovirus is the culprit.”

Molleston said Indiana has seen more cases of hepatitis than usual in the last couple months. In the majority of those cases, doctors were able to find the cause. A few cases may have, however, fit the CDC and WHO criteria for the current outbreak. Riley doctors didn’t find adenovirus in those cases, Molleston said, and no patients in Indiana required a liver transplant.

The CDC identified a cluster of cases in Alabama in October. The agency put out a nationwide health alert last week about the uptick in cases. Children in the U.S. are typically vaccinated against hepatitis, which is one reason the local doctors said they didn’t encounter a large number of hepatitis cases.

Christenson said emphatically that the hepatitis cases are not related to the COVID-19 vaccine, which has been a common refrain in recent weeks.

“When you look at the age groups for this condition, it’s quite broad. When you look at a lot of the children that were affected in Alabama, they were not even in the vaccination age. So, it’s not related to the vaccine against coronavirus. That is pretty certain.”

In addition, even though adenovirus has been found in some of the children with reported cases, it has not been found in all of them. That means there are many instances in which doctors can’t pinpoint the cause.

Christenson said it’s important not to become fixated on a single cause prematurely. Since doctors don’t know the cause or if cases in the U.S. and Europe are the same, it’s difficult to know how contagious this may be.

“The epidemiology is not yet known. How long it incubates, when you’re most infectious, how you’re infectious—none of that is known,” Molleston said.

Molleston characterized cases as “exceedingly rare” at this point and didn’t consider it a common threat for Hoosier kids.

Molleston and Christenson said typical hygiene advice applies to prevent the spread: wash your hands frequently, mask under certain circumstances and don’t go to work or school if you’re sick.

Here is the breakdown of hepatitis cases by country from the World Health Organization:

  • United Kingdom: 114
  • Spain: 13
  • Israel: 12
  • United States: 9
  • Denmark: 6
  • Ireland: 5
  • The Netherlands: 4
  • Italy: 4
  • Norway: 2
  • France: 2
  • Romania: 1
  • Belgium: 1