A total of 33 countries have recorded 920 probable cases of acute hepatitis in children so far, 270 more than in May, according to statements made by the World Health Organization (WHO) on Friday.

Half of the probable cases were recorded in Europe, 267 of which were in Britain while a third were recorded in the United States, according to WHO.

The mysterious cases are currently being investigated by the health authorities.

The outbreak of the disease was first recorded in April in Britain, after which it moved to other countries.

Hepatitis means inflammation of the liver and is often caused by a virus, according to the Centers for Disease Control and Prevention (CDC).

The liver is a vital organ that processes nutrients, filters the blood, and fights infections. When the liver is inflamed or damaged, its function can be affected.