The Centers for Disease Control and Prevention last week used data from the state of Alabama, where the majority of US cases have been found.
All of the children who later became seriously ill were generally healthy, with no immune system problems.
Although the most common signs were vomiting and diarrhoea, many children also had upper respiratory symptoms such as runny nose, sneezing and sore throat. Most of them had enlarged livers, jaundice and yellow eyes.
According to the World Health Organization (OMS), the mysterious outbreak of hepatitis cases in children has already spread to 20 countries, including Argentina.
Scientists believe it is related to adenovirus infection, which is commonly spread by close personal contact, respiratory droplets, and surfaces.
There are more than 50 types of adenoviruses, which cause the common cold. But preliminary evidence suggests that children with hepatitis were infected with adenovirus type 41, which causes symptoms such as stomach pain, vomiting, nausea and diarrhoea.