aerosolized in the air. that's prompted a lot of the concern. >> how deadly is exposure to anthrax? >> it can be deadly. there's three types, the inhalational type is the most concerning type. if someone got exposed to this, got a known infection, did not get treated, not vaccinated, 80, 90% of those people will die. this is potentially very concerning. it's sort of counter balanced by the idea that it is hard to get so the to speak, even if that situation, even if that laboratory to the actually become infected as a result of the spores in the air, it's not a particularly effective thing at infecting people. if it does take hold, as the a real problem. >> could it be more than 75 people we're talking about? how certain are we it's just the 75? >> i just talked to officials at the cdc, asked that same question. it's a good question. first of all, people outside the building i think they say pretty clear there's no risk outside