Los Angeles County health officials confirmed 102 new cases of AIDS in December, about the average number of new cases diagnosed in recent months, according to statistics released by the Department of Health Services. The new cases bring to 2,559 the number of acquired immune deficiency syndrome cases in the county since the epidemic began in 1981. There have been 1,560 deaths from the disease, which attacks the body's immune system. Of the cases, 92% occured in homosexual or bisexual men, 2% in heterosexual intravenous drug users and 2% in heterosexual people in contact with AIDS patients. Fifteen cases have developed in children. The statistics also show that 70% of the county's AIDS patients are white, 15% Latino and 14% black.