Figure 2a. Initial SARS-related lesion distribution of category II and maximal category III serial radiographic changes in a 28-year-old woman with SARS. (a) Frontal chest radiograph obtained 6 days after fever onset shows a focal air-space opacity (solid arrow) involving less than one-third of the left lower lung zone. Note partial obliteration of the right upper heart border (open arrow) by adjacent air-space opacity, involving less than one-third of the right middle lung zone (category II, extent score of 2). (b) Follow-up chest radiograph obtained 5 days later shows maximal progression of the lesions with extension of air-space opacity (solid arrow) involving more than two-thirds of the left lower lung zone and less than one-third of the right middle and lower lung zones (open arrows) (category III, extent score of 5). The patient recovered 11 days later.