>> reporter: this morning, health departments in at least 30 states are working with federal health officials to track down passengers who shared flights with patient number 1 and patient number 2 who had to be hospitalized in orlando. both men flew from saudi arabia. they underline that this is a new disease. that it isn't terribly contagious but does kill, more than 160 people have already died from this. most of them in the middle east. robin. >> we do have to keep that in mind. thank you. for more we turn to dr. richard besser who spent many years there at the cdc. in fact, that's where you were before we were lucky enough to have you join us. remind us again what mers is. >> stands for the middle eastern respiratory syndrome and it's a respiratory infection that can lead to pneumonia and the concerning thing is that up to a third of people, 30%, can die from this infection. >> the concern about its spreading here in the u.s. where does that stand? >> this weekend it was really...