Transmission link elusive – A possible association between pediatric hepatitis and adenovirus infection is currently under investigation.

Adenovirus serotypes 41 causes acute gastroenteritis primarily in children. Symptoms may include fever, diarrhea, vomiting, and abdominal pain, and last for approximately 10 days. Respiratory symptoms can occur in some individuals. The incubation period is around 8–10 days after which diarrhea develops and, in some cases, mild vomiting. Fever lasting 2–3 days may develop; severe dehydration is rare. The disease is usually self-limiting in immunocompetent individuals; however rare fatalities can occur in immunocompromised individuals. Asymptomatic infections are common, particularly in children. Adenoviruses are the third most common cause of infantile gastroenteritis after rotavirus and norovirus. Sporadic and endemic infections may occur year-round.

Adenovirus-associated gastroenteritis often occurs in clusters in schools, hospitals or military camps. Adenoviruses are spread person-person contact, by coughing and sneezing, by touching contaminated surfaces or by the fecal-oral route. Adenoviruses infections are not associated with contaminated food, but transmission can occur in water, through public water systems or in swimming pools; the latter are predominately associated with conjunctivitis.

As of April 21, 2022, WHO reported at least 169 cases of acute hepatitis of unknown origin have been reported from 11 countries in the WHO European Region and the United States. Cases have been reported in the United Kingdom of Great Britain and Northern Ireland (the United Kingdom) (114), Spain (13), Israel (12), the United States of America (9), Denmark (6), Ireland (<5), The Netherlands (4), Italy (4), Norway (2), France (2), Romania (1), and Belgium (1). Cases are aged 1 month to 16 years old. Seventeen children (approximately 10%) have required liver transplantation; at least one death has been reported. The outbreak has since spread to other countries, including Canada, and Japan.

As of April 28, 2022, the CDC has reported in the U.S., cases in several states, including Alabama, North Carolina, Illinois, Wisconsin and California.