Figure 1b. Category I SARS-related lesion. Serial radiographic changes in a 26-year-old man with SARS. (a) Frontal chest radiograph obtained 2 days after fever onset shows a somewhat nodular air-space opacity (arrow) involving one-third of the right upper lung zone (category I, extent score of 1). (b) Follow-up frontal chest radiograph obtained 7 days later shows maximal progression of the opacity (arrows) to involve less than two-thirds of the right upper lung zone (category I, extent score of 2). The patient recovered 6 days later.