Health officials in Los Angeles County have reported another 98 cases of AIDS, bringing the total number of local victims of the disease to 2,137. Another 143 suspected cases are under investigation. The death toll is now 1,225, or 57%, according to county Director of Health Services Robert Gates. As of Sept. 15, there were 24,859 cases reported nationwide, 13,689--or 55%--of them fatal, the federal Centers for Disease Control in Atlanta said. Los Angeles has the nation’s third largest number of victims of acquired immune deficiency syndrome; New York City and San Francisco have more.