The deaths of five children and what may be an unusual cluster of more than 100 cases of hepatitis in young children in the United States are under investigation by the Centers for Disease Control and Prevention, the agency said Friday.
The CDC said it was examining cases involving 109 children in 25 states and territories who had or have what the agency calls “hepatitis of unknown cause.”
Dr. Jay Butler, deputy director for infectious diseases at the CDC, said most of the children had fully recovered. But more than 90 percent were hospitalized, 14 percent received liver transplants and more than half had adenovirus infections, he said.
The CDC and experts abroad are exploring whether a type of adenovirus, a common virus that causes intestinal symptoms like vomiting and diarrhea, may be a factor in these cases. But the agency hasn’t determined a cause of the cases or a common link between them all, and cautioned against jumping to conclusions.
Dr. Butler called it “an evolving situation” at a news conference on Friday. He later added: “It is important to remember that severe hepatitis in children is rare, even with the potential increase in cases we are reporting today.”
An inflammation of the liver usually caused by a virus, hepatitis carries with it a number of complicating factors, side effects and stigma.
Hepatitis and liver failure are rare events in young children, especially otherwise healthy children, and so far, the actual number of hepatitis cases in the United States does not exceed the number typically observed.
The agency did not provide details about the children who died or where those deaths occurred.
The UK is investigating a much larger number, over 160 cases, of young children reported to have or have recently had hepatitis.
Hepatitis, an infection of the liver, usually occurs in adults and can be caused by viruses, which respond to drug treatment, or by alcoholism, some medications, or autoimmune diseases. Symptoms include yellow skin and eyes, nausea, and abdominal pain.
Dr. Butler also said there was no evidence so far that a Covid-19 infection or the Covid vaccine was linked to the US cases. The World Health Organization also said this week that the “great majority” of the children had not been vaccinated in the cases he had reviewed.
The scare began two weeks ago when the CDC issued an alert, citing nine cases of hepatitis among young children in Alabama that began last fall of this year. All had evidence of an adenovirus infection. Their median age was 2 years.
The problem for the CDC is determining whether the adenovirus is the cause or an innocent bystander, Dr. Butler said. Doctors don’t normally screen children for adenovirus infections (it’s not a notifiable disease in the United States), making it hard to disentangle cause and effect. He urged doctors to consider testing for adenoviruses if children were sick with certain symptoms.
The probability that nine randomly examined children have had adenovirus infections is not known. The virus is also seasonal, and the fall and winter, when Alabama children were sick, is adenovirus season.
To further complicate the situation, when the children were tested, the amount of virus, if any, was very low.
“We are working hard to determine the cause,” said Dr. Butler. Because hepatitis in children remains “a rare event,” he said, the search is difficult.
Other possibilities include environmental exposures, including animal exposure, or an immune reaction, with a reaction to an adenovirus “at the top of the list,” Dr. Butler said.
“We are casting a wide net,” he said.