Amid growing concern in both parties about how the federal government has handled several Ebola cases, top federal health officials again expressed confidence in the U.S. health care system, while facing criticism over how best to keep the virus out of the country in the future.

By far the biggest disagreement at this hearing was on the issue of travel restrictions, or a travel ban for people coming to the U.S. from west Africa - something that members of both parties have spoken in favor of in recent weeks.

"This is the question that the American public is asking; why are we still allowing folks to come over here," asked Rep. Tim Murphy (R-PA).

While CDC chief Dr. Tom Frieden had expressed opposition to a travel ban in past weeks, he seemed to soften that a little at the hearing, though he continued to express concerns that such a plan wouldn't work.

While most of the back and forth was pleasant, Frieden was pushed repeatedly for more by Rep. Steve Scalise (R-LA), the third ranking Republican in the House, as he wanted to know whether the White House has pressured the CDC to not support a travel ban.

Lawmakers also expressed frustration with the CDC over its aid for hospitals, as Frieden and others were unable to answer was what exactly had happened in Dallas that resulted in two nurses being infected with the Ebola virus.

"The investigation is ongoing," Frieden told lawmakers, which did not satisfy members of either party, as he said investigators had not narrowed down the possible causes."

"I still don't feel like we have a good answer as to why Nurse 1 and Nurse 2 contracted Ebola," complained Rep. Jan Schakowsky (D-IL).

Lawmakers also wondered why the second nurse infected was Ebola was allowed to fly from Cleveland to Dallas on Monday, all but accusing the CDC of not using common sense when it comes to dealing with the virus.

Despite some of the recent mis-steps, Frieden was again publicly confident that the U.S. health care system would be able to deal with Ebola.