steven riley is the professor of infectious disease dynamics. thank you for joining us.illion questions that people will have on whether it is safe to go back to work or send their kids back to school, how many people do we know -- how much of a percentage of the population do we think have had covid and are immune to it now? steven: i think averaged across countries, the whole of the u.k., it is a small percentage. on the order of 3% to 6% across the large population. but with an awful lot of uncertainty. but what we know from the other data and emerging serological data, there are indications that it might be higher than that. francine: what does that actually mean? if we reopen -- and i don't know whether it makes a difference if we reopen in a month or in four months -- unless we find medication that really works or a vaccine, is it going to spread like it has in march, or will it be more contained? steven: if we look back to early march, where it certainly was -- it was not appreciated how severe an infection it was. it spread very quickly. the differentch countries

professor steven riley, thank you for your expertise. >>> there's new evidence that covid-19 may have been in france for weeks earlier than previously thought. this is interesting. why this in the fight of the virus? we have a live report on that next. i didn't do it. #1 stain and odor fighter, #1 trusted. it's got to be tide. to give you the protein you need with less of the sugar you don't. [grunting noise] i'll take that. yeeeeeah! 30 grams of protein and 1 gram of sugar ensure max protein. now available in twelve-count. stock up today! get the perfectly grilled flavors of an outdoor grill indoors, and because it's a ninja foodi, it can do even more, like transform into an air fryer. the ninja foodi grill, the grill that sears, sizzles, and air fry crisps. you're having one more bite! no! one more bite! ♪ kraft. for the win win. for adults with moderately to severely active crohn's disease, stelara® works differently. studies showed relief and remission, with dosing every 8 weeks. stelara® may lower your ability to fight infections and may increase your risk of infections and cance