FIG 4.

Individual infection courses and virus levels. Viral N1 RNA (left axis) and infectious virus (right axis) in select individuals with detectable N1 for 1 (A), 2 (B), 3 (C), or 4 (D) consecutive weeks. (E) Examples of individuals with detection of N1 vRNA after a period of undetectable N1 following initial infection. (F) N1 vRNA and infectious virus by week of infection are plotted for individuals with incident infections during the course of the study, with negative (N) tests immediately before and after positive (P) tests stratified by the length of infection (1, 2, 3, or 4 consecutive positive weeks) and by those who experienced a postnegative positive test (a positive test after 1 to 3 negative weeks following initial infection). Dashed lines represent limit of detection; samples with result of “not detected” are plotted at half the limit of detection.