Parents have been urged to be on the lookout for signs of hepatitis in kids after 74 cases were detected in the UK. The condition can, in serious cases, lead to liver failure and experts have not yet pinned down the reason for the mysterious outbreak.

Prof Graham Cooke, NIHR Research Professor of Infectious Diseases, Imperial College London explained that hepatitis is a broad term to describe inflammation of the liver.

He said that this could be down to a range of issues – such as a virus of exposure to a toxic substance, including alcohol and some medications. “Globally, the most important causes are viruses that have adapted to infect the liver. “Early tests appear to have excluded these as a cause in the hepatitis currently under investigation.

So far, there have been 60 cases in England and 11 in Scotland of unexplained hepatitis, or liver inflammation, since the start of the year, most of them in children who are 2 to 5 years old. Case numbers in Wales and Northern Ireland haven’t been released.

Although no child has died, a “small number” have needed a liver transplant, said the UK Health Security Agency (UKHSA) on 8 April. This means they will have to take drugs that suppress the immune system for the rest of their lives, which will leave them at risk of infections.

Hepatitis is often associated with specific pathogens, such as the hepatitis C virus, but it can be triggered by many other things. There have previously been small clusters of cases caused by the hepatitis A virus, which can be spread by fecal contamination of food or water.

The hepatitis viruses A to E have all been ruled out in the current outbreak, though. Finding the cause will require carefully investigating every case to see if they have factors in common, says Graham Cooke, an infectious disease specialist at Imperial College London.