a deadly infection sweeping through six alabama hospitals. health officials are saying the harmful bacteria came from contaminated i.v. bags. nine of the patients infected have died, ten others have not recovered. the cdc is launching an investigation into the deaths. our elizabeth cohen live from atlanta. tell us what happened here. >> i want to tell you, ali, the ten people still recovering are not doing very well at all. and what happened here is very simple and very sad. these folks all had i.v. bags, and the material was found to be contaminated with a bacteria. this is a bacteria, ali, that is in the grout of your bathroom tile, you know, that black stuff. that's what that is. and so it was being pumped into their veins. ali? >> i guess it's not fatal when it's on the grout in your bathroom tiles, but it's a problem in the bags. how often -- you know a lot about this. how often do things like this in hospitals get contaminated?