A new virus distantly related to SARS is shaping up to be more deadly and spread even more quickly than the one that caused a global outbreak in 2003, killing 800 people. About 60 cases of the new virus, known as MERS, have been reported so far; most have been in Saudi Arabia and other parts of the Middle East. The source of MERS, a respiratory virus, remains completely mysterious to the team of scientists who have examined the cases so far. Some of the infected patients had no obvious exposure to anyone else with the virus. In addition to the Middle East, several cases have been reported in France, Great Britain, and Italy.