A virus that swept through the virtual reality environment of World of Warcraft has been used to study the possible effects of a pandemic in the real world.

An article in next month's issue of The Lancet Infectious Diseases journal suggests that the spread of the Corrupted Blood virus in September 2005 mimicked the way a real infection would spread.

"By using these games as an untapped experimental framework we may be able to gain deeper insight into the incredible complexity of infectious disease epidemiology in social groups," said the report.

Nina Fefferman, of the Department of Public Health and Family Medicine at Tufts University in Boston, co-author of the research used in the article, said that the online game showed what could happen if people were told immediately of the risk in a city such as London.

"Would there be panic and chaos, or would it allow them psychologically to accept the danger and act accordingly? What would happen if we made people feel too reassured?" she asked.

"These are all things that have a great impact on the number of people who would be affected and they are also things we just do not know. They could be of great value in helping us understand what the true emotional responses would be. "

The World of Warcraft infection came from the introduction of a powerful enemy called Hakkar, who released his 'corrupted blood' in a final offensive at the end of a fight with the strongest characters in the online world.

This final dying attack was only supposed to kill off weakened nearby opponents, but spread outside the original environment by infecting a virtual pet.

The virus created a 'digital disease' that instantly killed low level characters who came into contact with it, but eventually wiped out powerful characters.

Fefferman said that the virus also showed other properties of a real-world infection by having immune characters act as carriers.

Characters controlled by computers owned by Blizzard, the maker of the game, were immune, but continued to spread the infection to real-life players logging in to the service.