An illustrated profile of a child that contains a pink overlay of the hepatitis virus on a neutral background.
Illustration: PGN

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What you need to know

  • More than 900 unexplained hepatitis cases have been reported, mostly in children under 6, in 33 countries and 42 U.S. states.
  • There is no evidence that the outbreaks are linked to any COVID-19 vaccines.
  • One small study found a possible association between long COVID and hepatitis of unknown origin, but a CDC report found no increase in pediatric hepatitis hospitalizations in the U.S. compared to pre-pandemic levels.
  • Parents can watch for hepatitis symptoms and encourage good hygiene to keep their children safe.

In early April, the U.K. reported dozens of mysterious hepatitis cases in children under age 10 with no known cause. As of late June, 920 cases have been reported in nearly three dozen countries—and the cause remains elusive. Here’s everything we know about the hepatitis outbreak.

What is hepatitis?

Hepatitis is inflammation, or swelling, of the liver. The condition is usually caused by infection with hepatitis viruses, named hepatitis A through E, with hepatitis A, B, and C being the most common in the U.S. Hepatitis can also be caused by exposure to certain medications and poisons and by chronic, excessive alcohol consumption. Viral hepatitis is spread through contact with the bodily fluids of an infected person, including blood, semen, and feces.

Jaundice, or yellowing of the skin and eyes, is one of the easiest hepatitis symptoms to spot. Other common symptoms are dark-colored urine, light-colored stool, fever, fatigue, joint pain, loss of appetite, nausea, and vomiting. While some types of hepatitis are treatable, others can be life-threatening and may require a liver transplant. 

Where are the outbreaks happening?

On April 8, U.K. officials announced that they were investigating dozens of hepatitis cases of unknown origin in young children, most between the ages of 2 and 5. No known hepatitis viruses were detected in the affected children. The following week, the CDC and the Alabama Department of Health announced an investigation into nine mysterious pediatric hepatitis cases in the state, which were first reported in October 2021. The outbreaks have spread rapidly in the U.S., with 42 states reporting 302 cases, 20 liver transplantations, and 11 deaths as of late June. Over 900 cases have been reported in dozens of countries in Europe, North America, Latin America, and Asia. Some U.K. experts believe that the outbreak may have peaked in the country, as recent data indicates the rate of new cases has slowed. 

What is causing the outbreaks?

One reason that scientists are concerned about the hepatitis outbreaks is that there is still no clear cause for the illnesses. The cases aren’t connected to any common hepatitis viral strain, and no common drug or toxin exposure has been identified. 

Adenovirus 

The primary suspect behind the cases is adenovirus, a family of dozens of viruses that cause a host of common health conditions, including colds, bronchitis, pneumonia, and gastroenteritis, sometimes called stomach flu. Adenovirus infections are usually mild, but in rare instances they can be serious and even life-threatening, particularly in people with weak immune systems. There are rare cases of adenovirus infections resulting in hepatitis, most commonly in immunocompromised children. But adenovirus type 41, which has been detected in some of the affected children, is not associated with hepatitis in children with healthy immune systems. Adenovirus has been detected in around 45 percent of the affected children in the U.S., 55 percent in Europe, and 65 percent in the U.K. One theory being investigated is that an adenovirus surge is causing more infections than usual and bringing to light a rare complication. Another theory suggests that lack of immune system exposure to adenovirus during the pandemic may have made young children more susceptible to serious complications, like hepatitis.

SARS-CoV-2

Although the virus that causes COVID-19 does not appear to be a direct cause of the hepatitis outbreaks, a potential connection is still being investigated. A majority of the affected children tested negative for COVID-19 and were not recovering from recent COVID-19 infections. A CDC report on hepatitis of unknown origin cases through March found no increase in hepatitis-related pediatric hospitalizations in the U.S.

Experts are continuing to explore a potential connection between the hepatitis outbreaks and COVID-19. One CDC study found that 26 percent of patients had previously had a COVID-19 infection at the time of hepatitis diagnosis. A small case study investigating five children who developed hepatitis after recovering from COVID-19 indicates there may be a connection between the two conditions in some hepatitis cases, but no link has been demonstrated yet. One hypothesis being investigated is that COVID-19 infection alone or coinfection with adenovirus may make children more susceptible to hepatitis. 

Environmental exposure 

Exposure to certain drugs and toxins in the environment can trigger hepatitis in children. Early analysis in the U.K. considered exposure to dogs, which was reported in around 70 percent of affected children, and the common pain medication acetaminophen, which can cause liver damage in very high doses. The connections are likely coincidental given the high rate of both dog ownership and acetaminophen use in the U.K. No common environmental exposures have been identified in U.S. cases.

What can I do to keep my child safe?

  • Watch for hepatitis symptoms, including yellowing of the skin and eyes, dark-colored urine, light-colored stool, fever, fatigue, and vomiting. Contact a health care provider if you’re concerned your child may have hepatitis. 
  • Keep your child up to date on vaccinations, including the hepatitis A and hepatitis B vaccines.
  • Encourage good hygiene, including frequent hand washing and avoiding touching the mouth, nose, and eyes with unwashed hands.
  • Avoid contact with people who are sick.

Misinformation about hepatitis cases in children

The lack of a confirmed cause for the hepatitis cases in children has resulted in the rapid spread of misinformation about the outbreaks. Unlike the potential causes being investigated by health officials and researchers, which were identified by blood and tissue analysis and environmental surveys, false claims about the origins of the outbreaks are based on wild speculation and anti-vaccine conspiracy theories.   

There is no evidence that the hepatitis outbreaks are linked to COVID-19 vaccines, either directly from the vaccine or passed through a vaccinated parent who is pregnant or breastfeeding. Most of the affected children are not vaccinated against COVID-19, and many are too young to even be eligible for vaccination in their country. Similarly, the baseless claim that vaccination during pregnancy or breastfeeding causes hepatitis in an infant is not supported by any known cases or scientific evidence. Many of the children are too old to have been born or breastfed after COVID-19 vaccine rollouts.