Figure 4. Individual infection courses and virus levels.

Viral N1 RNA (left axis) and infectious virus (right axis) in select individuals with detectable N1 for A) one, B) two, C) three, or D) four 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 is plotted for individuals with incident infectious during the course of the study, with negative (N) tests immediately before and after positive (P) tests, stratified by the length of infection (one, two, three or four consecutive positive weeks) and those who experienced a post-negative positive test (following 1–3 negative weeks). Dashed line represents limit of detection, samples not detected plotted at half the limit of detection. PFU, plaque forming units.