WASHINGTON — Representative Darrell Issa, Republican of California, used the first case of Ebola in New York to step up his criticism of the Obama administration’s response to the crisis during a congressional hearing on Friday morning.

“I think we all know that the system is not yet refined to where we could say it is working properly,” Mr. Issa told the House Committee on Oversight and Government Reform, which he leads, only hours after a doctor in New York who had treated Ebola patients in Guinea tested positive for the virus.

Mr. Issa also questioned whether the administration had chosen the correct person when it named Ron Klain as its Ebola coordinator. He criticized the Centers for Disease Control and Prevention’s initial response to Ebola cases in the United States, and accused the C.D.C.'s director, Dr. Thomas R. Frieden, of making untrue statements about how Ebola can be transmitted.

“When the head of the C.D.C. says you can’t get it with somebody on the bus next to you, that’s just not true,” Mr. Issa said, adding that a person carrying the virus could transmit it on public transportation by vomiting on another passenger.