(CNN) -- An investigation continues into cases of acute hepatitis with unknown causes among children who had adenovirus infections.
In a health advisory Thursday, the US Centers for Disease Control and Prevention alerted health care providers and public health authorities to the investigation and recommended that providers consider adenovirus testing in children with hepatitis when the cause is unknown, adding that testing the blood in whole -- not just blood plasma -- may be more sensitive.
The advisory notes that "a possible association between pediatric hepatitis and adenovirus infection is currently under investigation."
Last week, public health officials in the United States and the United Kingdom announced that they had launched an investigation into cases of severe acute hepatitis in children. At the time, the World Health Organization had identified 74 cases among children across the UK, and Alabama health officials identified nine cases of hepatitis in children, ages 1 to 6, who also had tested positive for adenovirus since October. None of the children had Covid-19.
In its latest health advisory, the CDC asks that health care providers or state public health authorities alert the agency to any child younger than 10 who may have been diagnosed with hepatitis due to an unknown cause since October.
"In November 2021, clinicians at a large children's hospital in Alabama notified CDC of five pediatric patients with significant liver injury, including three with acute liver failure, who also tested positive for adenovirus. All children were previously healthy," CDC officials wrote. "Case-finding efforts at this hospital identified four additional pediatric patients with hepatitis and adenovirus infection for a total of nine patients admitted from October 2021 through February 2022; all five that were sequenced had adenovirus type 41 infection identified."
Hepatitis is inflammation of the liver, a vital organ that processes nutrients, filters the blood and helps fight infections. When the liver is inflamed or damaged, its function can be affected.
Most often, hepatitis is caused by a virus, and adenoviruses are a common type of virus spread from person-to-person that can cause a range of mild to more severe illnesses. But these viruses are only rarely reported as a cause of severe hepatitis in healthy people.
The CDC said in the advisory that "While there have been case reports of hepatitis in immunocompromised children with adenovirus type 41 infection, adenovirus type 41 is not known to be a cause of hepatitis in otherwise healthy children."
"It's not a common presentation, not at all," said Dr. Ashlesha Kaushik, a spokesperson for the American Academy of Pediatrics. "This is quite surprising."
Children's caregivers should be on the lookout for symptoms including diarrhea and vomiting. If a child has abdominal pain or develops a fever, fatigue or muscle pain, they should get checked by a doctor. Symptoms of jaundice -- including yellow eyes, dark urine or light-colored stools -- are physical signs of a problem with the liver.
To avoid adenovirus, Kaushik said, parents should urge their children to regularly and thoroughly wash their hands.
There is no vaccine for adenoviruses in children. Adenoviruses tend to linger on surfaces, she said, and alcohol-based hand sanitizers don't work well against them.
"Thorough handwashing with soap and water is the best thing," Kaushik said. "Keeping distance from anybody who's sick with coughing and sneezing, and teach your children to cough or sneeze into their sleeve." Essentially, she said, keep up with all the good habits people have learned to prevent Covid-19.
Because adenovirus has a gastrointestinal component, she also advises parents and adults at day care centers to be meticulous about their own hand hygiene after changing diapers.
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