Figure 3: RNA and viral loads in individuals sampled repeatedly.

Viral RNA levels as determined by qRT-PCR amplification of N1 gene (left y-axis) and infectious virus as determined by plaque assay (right y-axis) for a subset of subjects. Viral RNA was detectable for one (A), two (B), three (C) or four (D) consecutive weeks. E) Representative individuals in which viral RNA was detected again after a period of negative tests. F) Average viral RNA levels and infectious virus (+/− SD) for all incident infections during first, second, third and fourth week of consecutive infection. Viral RNA and infectious virus levels were calculated per nasopharyngeal swab. Letters at the beginning of graph titles indicate site of origin. Black dotted line is the limit of detection for viral RNA. Grey dotted line is the limit of detection for infectious virus. pfu, plaque forming units.