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CDC issues new report on severe, unusual hepatitis in kids: What to know

As more states in the U.S. investigate cases of severe hepatitis with an unknown cause, here's what we know so far.

The mysterious outbreak of hepatitis in children in the U.S. and around the world appears to be growing, as more state health departments report that they are investigating cases.

The Centers for Disease Control and Prevention issued a report Friday about nine cases of hepatitis, an inflammation of the liver, in Alabama. North Carolina, Delaware, Wisconsin, Illinois, Georgia and New York are also investigating at least 10 cases, NBC News reported, including one death.

The World Health Organization has also identified about 170 cases in 16 countries, including at least one death and 17 liver transplants.

Both the CDC and WHO are investigating whether the hepatitis is possibly caused by a strain of adenovirus, specifically adenovirus 41. Adenoviruses are common and usually cause cold-like symptoms, like sore throat, fever, and stomach pain or diarrhea.

Adenovirus 41 “is not known to be a cause of hepatitis in otherwise healthy children,” the CDC said in its initial alert about the Alabama cases, adding that all were in previously health children.

Hepatitis is most often caused by hepatitis viruses A, B, C, D and E. However, the Alabama cluster of cases and the others are not caused by any of the usual hepatitis viruses.

CDC report on hepatitis in Alabama kids: What we know so far

The nine children in Alabama — between 1 and 6 in age, with a median age of about 3 — were diagnosed between October and February, and all became ill enough to merit hospitalization. Three developed acute liver failure, and two required liver transplants. Seven were girls. All patients lived in different parts of the state, so they likely had no connection to each other.

COVID-19 and the COVID-19 vaccine do not appear to be related to the illness: None of the children had been vaccinated, and none tested positive when admitted to the hospital or had a previous, documented case.

All nine children tested positive for adenovirus, with five testing positive for adenovirus 41. Adenovirus has not been confirmed as the cause, however.

Symptoms among the patients included: vomiting, diarrhea and upper respiratory symptoms, as well as signs of liver problems, such as yellowing in the whites of the eyes and an enlarged liver.

“We’ve been watching these cases in the U.S. and throughout parts of Europe with great interest for some time now,” Dr. Andrew Pavia, a pediatric infectious disease epidemiologist at Intermountain Primary Children’s Hospital in Salt Lake City, told TODAY. “It’s only recently that the possible connection between the hepatitis cases and adenovirus 41 has been considered.”

Pavia called the number of reported cases "moderately large," so "we have to keep an eye on" it.

Dr. Esther Israel, associate unit chief of pediatric gastroenterology and nutrition at Mass General Hospital for Children, added that because adenoviruses have not commonly caused hepatitis in healthy children before, "other sources are still being sought" for the cause.

Dr. David Hill, a Wayne County, North Carolina-based pediatrician and the official spokesperson of the American Academy of Pediatrics, agreed.

“Adenovirus 41 is the prime suspect but has not yet been the proven cause of this syndrome,” he said. “The two may be connected, or the cause of these cases may be something entirely new or an evolving kind of infection that we need to identify as quickly as we can.”

A Monday briefing from the Health Security Agency in the U.K. — where more than 100 cases have been reported, the most of any country — pointed out that adenovirus cases dropped in the country during the pandemic but have since risen higher than pre-pandemic levels.

It's still not clear, though, how an adenovirus may cause liver inflammation in healthy children. The U.K. agency is investigating a few theories, including a new strain of adenovirus, an undiscovered co-infection or toxin, or an "increased susceptibility" in kids after months of staying home during the pandemic.

Knowing about the possible connection between adenovirus and these severe cases of hepatitis means physicians can broaden their search when diagnosing new cases of hepatitis. “When I treat hepatitis, I don’t typically test bloodwork for adenoviruses,” Hill said. “Because of this advisory, I will be doing so now.” 

Rare liver damage in kids: What parents should look for

While adenoviruses and hepatitis share symptoms, such as diarrhea and nausea, Hill explained that hepatitis is far more concerning with unique symptoms to be aware of.

“Adenoviruses typically run their course without needing medical intervention,” he said. Hepatitis, on the other hand, “sometimes leads to hospitalization and may even require a liver transplant.”

Dr. Nipunie Rajapakse, a pediatric infectious disease specialist at Mayo Clinic Children’s Center, added: “Most of the treatment for hepatitis involves what we call supportive care that supports the body systems until the liver is able to heal and recover from the inflammation.”

There is no specific treatment for adenoviruses.

To differentiate between adenovirus symptoms and hepatitis symptoms, parents should keep an eye on sick children and look out for severe abdominal pain, fever, dark-colored urine or light-colored stools. The most telling symptom to be aware of is jaundice, or a yellow coloring in the skin or in whites of the eyes, Rajapakse said.

Hepatitis and adenovirus: Are these cases contagious?

One of the most important reasons to understand the possible connection between adenoviruses and the unusual hepatitis cases is, according to Hill, adenoviruses are "much easier to contract than hepatitis."

As Israel put it, "If indeed adenovirus is the responsible virus, this potentially is contagious."

Good hygiene can help prevent transmission of either illness.

“At this time, practicing good healthy habits, such as washing or sanitizing hands frequently, staying home when you are ill, and staying away from sick people is the best method for prevention,” said Dr. Michael Fullmer, a pediatrician at Utah Valley Pediatrics in Saratoga Springs, Utah.

He added that adenoviruses can spread through respiratory droplets, but it’s “normally spread through direct contact” with other humans or surfaces where the virus is present. Adenovirus 41 is most often spread through fecal particles passing from one person to the mouth of another, according to the CDC.

Public health officials still need time to understand the root of thes hepatitis cases. “It’s dangerous to speculate too early on,” Pavia advised. “The exact cause and implications of what has happened in Alabama remains to be seen.” 

Echoed Israel: “At this stage, it is hard to know how common this will be, but we may very well see more if it is infectious. Parents should be alert to the signs of hepatitis and should contact their health care professional if they are concerned."