Aging and HIV have parallelism in immunodeficiency status because of the appearance of infections or relapse leading to death in both conditions. HIV-RNA is predictor for HIV progression correlated with CD4+ depletion. CD4+ and plasma zinc levels (zincaemia) may be predictors for infections relapse in aging because of zinc relevance for normal immune efficiency against infections and for CD4+ growth. Moreover, zincaemia decreases in aging and infection. A total of 67 elderly subjects affected by infections resistant to antibiotic therapy were recruited. A total of 28 HIV+ subjects with HAART therapy were also used. CD4+ depletion (507 mm3) and zincaemia deficiency (76 microg/dl), as compared to CD4+ (700-1100 mm3) and zincaemia (85-100 microg/dl; age 40-75 years) normal ranges, are possible limits (Cox hazard regression) for severe infections relapse, such as chronic obstructive bronchitis and bronchopneumonia by bacteria or Candida complication, in aging. CD4+ and zincaemia values are within the lower limits of normal range in urinary tract infections. Zincaemia and HIV-RNA or CD4+ are inversely correlated (r = 0.57 and r = 0.72, respectively) in HIV+ HAART treated subjects. Consequently there is no appearance of opportunistic infections. Parallelism between aging and HIV may exist because of the resemblance in marked zinc deficiency and CD4+ depletion with high scores in relative risks for severe infections relapse. Supplementing zinc (12 mg Zn++/day) for one month in infected elderly subjects and HAART therapy in HIV+ subjects reduces risk scores in CD4+ and zincaemia deficiencies for infections relapse, suggesting that the zinc beneficial effect may be independent either by HIV-virus or pathogen agents involved. While HAART may reduce the occurrence of opportunistic infections in HIV by means of also major zinc bioavailability, supplementing zinc can be recommended in elderly people as resistance to infections. Since zinc deficiency is correlated with CD4+ depletion, this latter may also be good diagnostic marker to detect 'clear immunodeficiency' in aging, as in HIV condition.