The Sars virus could be the result of a merger between viruses carried by birds and mammals, say researchers. The finding is based on a genetic analysis of the coronavirus, which causes the disease, and others that are closely related. A similar phenomenon is responsible for the emergence of new types of flu virus. The research, by a team from the University of Toronto, is published in the Journal of Virology. Sars killed 774 people and infected as many as 8,000 in a world-wide outbreak earlier this year. China and Hong Kong bore the brunt of its effect, but Taiwan,...