By Jennifer Rigby and Natalie Grover LONDON (Reuters) – Health authorities around the world are investigating a mysterious increase in severe cases of hepatitis – inflammation of the liver – in young children. Below is a summary of what is known about the outbreak: WHAT’S HAPPENED? More than 190 cases have been identified, with the majority in Britain, which has reported 111 cases since January. Other countries including the United States, Israel, Denmark, Ireland, the Netherlands and Spain have also reported smaller numbers of cases. WHY IS IT CAUSING CONCERN? Mild paediatric hepatitis is not…