a Radiographs of the chest of RM before inoculation and on day 3 and day 6 post infection with SARS-CoV-2. The red circled areas are regions of interstitial infiltrates indicative of viral pneumonia. b, c Lesions in the lungs. A view of the ventral lungs of an infected animal obtained at necropsy on day 3 and 6 post infection, showing severe hemorrhage and necrosis of lung (white circles). Scale bar, 5 mm. Viral loads in trachea, bronchus, right and left upper, middle, and lower lung lobes on day 3 (d) and day 6 (e). Red bar, RM2; black bar, RM6; pink bar, RM3; orange bar, RM5. Error bars mean standard deviation from two technical repeats. L.O.D. limit of detection, 103–104 copies/g as the tissue weight varies.