ALVIN Z. ROSENFELD, 73, a journalist who covered wars in Europe, Africa and the Middle East, died of cancer Saturday at Georgetown University Hospital in Washington, D.C. Mr. Rosenfeld had worked over the years for United Press, NBC News and the Washington Post, among other publications. He died Saturday at Georgetown University Hospital. He worked for the Smithsonian Institution from 1978 to 1986, directing its public affairs office and starting the Smithsonian News Service. In 1986, he was vice director of the U.S. Holocaust Memorial Museum.