SCIENTISTS at Southampton University have made a breakthrough in understanding how a contagious vomiting and diarrhoea bug often found in hospitals and cruise ships can spread.

Until now little has been known about the norovirus because of the difficulty in studying the virus in a laboratory.

However, by looking at a similar virus which affects rats scientists believe they will develop a greater understanding of the virus and devise ways to control it.

Professor Ian Clarke, who heads the virus group at Southampton University said: "The human noroviruses have been exceedingly difficult to work with as there is no cell culture system to propagate these viruses, and as a result very little is known about their biology."

He added: "This study represents the culmination of a ten-year research quest in Southampton to obtain recovery of a live norovirus from its nucleic acid."

Researchers from the Washington University School of Medicine are also taking part in the project that was funded by a Wellcome Trust grant.

Earlier this year six wards had to be closed at Southampton General Hospital including elderly care wards and one trauma and orthopaedics ward because of an outbreak of the norovirus.

A total of 44 patients and 26 staff displayed symptoms and the hospital was forced to tell people not to visit the site if they had suffered from diarrhoea or vomiting during the previous 72 hours.

Hospital visitors were also reminded to wash their hands or use the alcohol gel provided whenever they arrived or left wards or departments.