A–D, Molecular viral loads on first and third measurements (circles) and second measurement (crosses) for influenza A from the Influenza Resistance Information Study (IRIS) (A) and the household transmission study (HTS) (B) and for influenza B from the IRIS (C) and the HTS (D). E–H, Difference between observed and expected molecular viral load (VL) at the second measurement, with a histogram summarizing the differences, for influenza A from the IRIS (E) and the HTS (F) and for influenza B from the IRIS (G) and the HTS (H). The second measurement (crosses) was collected by self-swab in the IRIS (A, C, E, G) and by a healthcare professional in the HTS (B, D, F, H). For the IRIS, the lower limit of detection (LLOD) of the influenza A assay was 54 viral particles per milliliter (vp/mL), and the lower limit of quantification (LLOQ) was 131 vp/mL; the LLOD of the influenza B assay was 168 vp/mL, and the LLOQ was 194 vp/mL. For the HTS, the LLOD of the influenza A and B assays was 550 copies/mL, and the LLOQ was 900 copies/mL.