whistle-blowers accuse some va stras of falsifying records and covering it up, but thanks to that reporting here at cnn the head of the va had to answer some pretty tough questions on thursday on capitol hill. >> is in your judgment based on what you know, are people, quote-unquote, cooking the books? is that, in fact, a problem within the health care system? >> i'm not aware, and other than a number of isolated cases where there is evidence of that. but the fact that there is evidence in a couple of cases behooves us to go and take a thorough look. >>> and i can promise you cnn will stay on top of this story. >>> in other news a disease called middle east respiratory syndrome, has put a lot of people on edge, it kills about a third of known patients. nearly all of them were infected in saudi arabia. but some have flown to the united states. the cdc and local health officials are tracking down hundreds of people who were on those multiple airplanes with these individuals, and senior medical correspondent elizabeth cohen has a look behind the scenes. >> reporter: we're here at the cdc's emer