And the why is that this virus unfortunately is infectious for two, possibly three days before people get symptoms and maximally infectious just around the time they get symptoms. [SEP] And so therefore picking out the people who actually might have infections or much higher than average rate of infection because they'd been close to someone who has actually got the infection, we know they've got the infection, those are the group who are the biggest risk of unwittingly having an infection without symptoms and then spreading it for two or three days.
Topic continuity: continue