Evidence of clonal mosaicism from mtDNA mutations over 3 years in vivo. (A) Schematic diagram of somatic mtDNA mutations in human cells. Each cell contains multiple mitochondria, which, in turn, contain multiple copies of mtDNA. (B) Examples of variable mutations in vivo across 3 years of observation that reflect clonal mosaicism in 1 donor. (C) Spearman correlation of 57 time points (ordered by relative time of sampling) across time points sampled. Correlation value is measured with the baseline sample. (D) Heteroplasmy of 2394T>A allele, which is associated with human RSV detection in this donor; inset shows heteroplasmy levels for 2394T>A for ∼23 days after the initial detection of RSV. (E) Corroboration of 2394T>A allele at the time of RSV infection using whole-genome bisulfite sequencing data at the 6 time points (on specific days) that correspond to infection. (F) Heteroplasmic mutations specific to the day of detection for adenovirus (ADV; 1575A>G) and human rhinovirus (HRV; 10310T>G) infections.