No, he measured viral load. The number of viruses in patients. As in "the number of viruses present per cm³ of air breathed out", "the number of viruses on one

No, he measured viral load. The number of viruses in patients. As in "the number of viruses present per cm³ of air breathed out", "the number of viruses on one swab from the patient's throat" or similar. There are several ways to measure this, they correlate but are not identical.