Four new cases of a new SARS-related coronavirus in the Middle East were reported by the World Health Organization on Friday. Of the six known cases — all in Saudi Arabia or Qatar — two have been fatal. Only two were clearly connected; the patients were from the same Saudi family, which suggests that the virus can be transmitted from human to human. Two other members of the same family, from the Saudi capital, Riyadh, previously were ill with similar symptoms, one of whom died, the agency said. It asked all countries to step up surveillance of rapid-onset pneumonia. The Saudi Health Ministry put out a statement reassuring citizens that there was “no cause for worry — the discovered cases were few and isolated.” SARS — severe acute respiratory syndrome — emerged in China in 2002 and killed about 9 percent of the 8,273 people it infected before disappearing.