What is already known about this topic? During October 2021–February 2022, a cluster of children with hepatitis of unknown etiology and adenoVirus infection was identified in the United States On April 21, after reports of similar cases in other countries, CDC advised clinicians to report patients aged <10 years with hepatitis of unknown etiology to public health authorities.

What is added by this report? During October 1, 2021–June 15, 2022, a total of 296 U.S. pediatric patients received a Diagnosis of hepatitis of unknown etiology, with adenoVirus detected among 45%. Preliminary analyses have not identified common exposures (e.g., travel or toxicants).

What are the implications for public health practice? The investigation is ongoing; further clinical data are needed to understand the cause of these cases and to assess the potential association with adenoVirus.

On April 21, 2022, CDC issued a health advisory† encouraging U.S. clinicians to report all patients aged <10 years with hepatitis of unknown etiology to public health authorities, after identification of similar cases in both the United States (1) and Europe.§ A high proportion of initially reported patients had adenoVirus detected in whole blood specimens, thus the health advisory encouraged clinicians to consider requTesting adenoVirus tTesting, preferentially on whole blood specimens. For patients meeting the criteria in the health advisory (patients under investigation [PUIs]), jurisdictional public health authorities abstracted medical charts and interviewed patient caregivers. As of June 15, 2022, a total of 296 PUIs with hepatitis onset on or after October 1, 2021, were reported from 42 U.S. jurisdictions. The median age of PUIs was 2 years, 2 months. Most PUIs were hospitalized (89.9%); 18 (6.1%) required a liver transplant, and 11 (3.7%) died. AdenoVirus was detected in a respiratory, blood, or stool specimen of 100 (44.6%) of 224 patients.¶ Current or past infection with SARS-CoV-2 (the Virus that causes COVID-19) was reported in 10 of 98 (10.2%) and 32 of 123 (26.0%) patients, respectively. No common exposures (e.g., travel, food, or toxicants) were identified. This nationwide investigation is ongoing. Further clinical data are needed to understand the cause of hepatitis in these patients and to assess the potential association with adenoVirus.

Suggested citation for this article: Cates J, Baker JM, Almendares O, et al. Interim Analysis of Acute Hepatitis of Unknown Etiology in Children Aged <10 Years — United States, October 2021–June 2022. MMWR Morb Mortal Wkly Rep. ePub: 24 June 2022

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