Hence, from an epidemiological standpoint the aforementioned observations suggest that genotype-phenotype associations for CCL3L1 copy number and CCR5 genotype may differ significantly depending on the characteristics and disease stage of the subjects evaluated (e.g., those enrolled from the early stages of their infection as part of a natural history cohort versus accrual of subjects during the later stages of disease, or those enrolled as part of a clinical trial, or selection of subjects based on specific clinical or laboratory characteristics). The gene discussed is CCR5; the disease is infection.