The results showed that a CD4 + T-cell count below 200 cells/μL was a strong independent risk factor for infection with both C. parvum (adjusted odds ratio [aOR] = 8.4; 95% confidence interval [CI]: 3.2–21.7; p < 0.001) and E. bieneusi (aOR = 6.5; 95% CI: 2.1–19.6; p = 0.002). This evidence concerns the gene CD4 and infection.