The number of American children affected by acute hepatitis of unknown cause continues to grow, the U.S. Centers for Disease Control and Prevention said on Wednesday.
So far, the agency's investigation has spotted 180 pediatric cases in 36 states and territories over the past seven months. That's an increase of 71 from the last time numbers were released on May 5.
However, the CDC stressed in a statement that many of the new domestic cases are "retrospective" — meaning they were cases that are now being counted but which happened as far back as October 2021.
There have been no reported deaths since February, the agency added, and the number of children requiring liver transplants is 9% of cases, after the additionally discovered cases were added to the count. The CDC previously reported that 15% of children had required liver transplants, based on its May 5 calculations.
There also are hundreds of other pediatric hepatitis cases that have been reported in countries around the world, according to the World Health Organization.
"It's unusual because this is occurring in normal, healthy kids who don't have an underlying condition," said Dr. Tina Tan, an infectious disease doctor with the Ann & Robert H. Lurie Children's Hospital of Chicago. "Nobody knows the true cause, and what makes it more scary is that these kids develop very severe hepatitis."
About half of the children involved in the U.S. cases have had some form of adenovirus. This continues to be a strong indicator of what could be driving these cases, the CDC said.
"It's important to note that severe hepatitis in children remains rare," the agency said. "However, we encourage parents and caregivers to be aware of the symptoms of hepatitis — particularly jaundice, which is a yellowing of the skin or eyes — and to contact their child's health care provider with any concern."
The CDC is conducting additional lab tests to look more closely at the adenovirus genome and other possible pathogens, which could include SARS-CoV-2, the virus behind COVID-19.
One cause that has definitely been ruled out: the COVID-19 vaccine.
"COVID-19 vaccination is not the cause of these illnesses, and we hope that this information helps clarify some of the speculations circulating online," Dr. Jay Butler, the CDC's deputy director for infectious diseases, said at a media briefing on May 6.
Meanwhile, the agency is communicating with key medical groups and providing reporting and laboratory guidance for doctors who may find hepatitis of unknown cause in their patients. As part of this communication effort, the CDC is hosting a Community Outreach and Clinician Activity call on Thursday to provide updates and provide an opportunity for clinicians to ask questions.
Additional investigation updates will be provided weekly.