WASHINGTON (AP) -- The White House is conceding there were shortcomings in the response to an Ebola patient's care in Texas that has now resulted in two health care workers testing positive for the disease.

White House spokesman Josh Earnest noted that Centers for Disease Control and Prevention director Dr. Tom Frieden had declared that even one health care worker being exposed was unacceptable.

"So that is an indication that there were shortcomings," Earnest said.

White House press secretary Josh Earnest speaks during the daily briefing in the Brady Press Briefing Room of the White House in Washington, Wednesday. (AP Photo/Pablo Martinez Monsivais)

Signaling urgency in the U.S. response, President Barack Obama canceled his political travel Wednesday to meet with his Cabinet on the Ebola outbreak that has created a crisis in West Africa and the new developments in Texas.

"We're operating in a pretty dynamic environment right now," Earnest said, adding that the administration was addressing the situation in a "tenacious" manner.

Hours before Obama canceled his trip, officials confirmed that a second nurse at a Dallas had tested positive for the virus after treating an Ebola patient who later died. The disclosure raised new fears regarding the exposure by other health care workers. Officials also revealed that the nurse was on a commercial flight the evening before being diagnosed.

Asked how the nurse was able to fly to and from Ohio over the weekend, Earnest said, "It's not clear what protocols were in place and how those protocols were implemented."

Obama called off a trip to New Jersey and Connecticut. Instead, he was to convene Cabinet officials coordinating the government's Ebola response at the White House. He planned to speak to reporters at the end of that meeting.

The change came as a second health worker in Dallas who provided care for the first Ebola patient diagnosed in the U.S. tested positive for the disease. The two health care workers were infected after treating a Liberian man who died of Ebola last week.

Obama had planned to speak at a fundraiser for Senate Democrats in Union, New Jersey, and then headline a rally for Connecticut Gov. Dannel Malloy.

Frieden also revealed that the second health care worker took a flight from Cleveland to the Dallas area. Frieden said the health care worker traveled to Ohio before she knew that the first nurse had been diagnosed. She was undergoing self-monitoring at the time.

Sen. Rob Portman, R-Ohio, called on Obama to appoint a single administration official to coordinate the U.S. Ebola strategy and said the second infected health care worker "demonstrates why our government must be more proactive in the fight to prevent the spread of Ebola."

Asked if Obama was considering appointing an Ebola "czar" as Portman suggested, Earnest said the current response was well coordinated from the White House and involved various agencies responsible for different aspects of the administration's actions. The White House coordinator is Lisa Monaco, Obama's top adviser for homeland security and counterterrorism.

Two Republican lawmakers with influence over transportation policy called for a temporary travel ban from affected West African countries on Wednesday and asked the Obama administration to spell out plans for how to prevent the spread of the disease through the nation's transportation network.

House Transportation and Infrastructure Committee Chairman Bill Shuster of Pennsylvania and Sen. John Thune of South Dakota, the senior member of the Senate's transportation committee, sent a letter to the Transportation and Homeland Security departments stating that even if chances of an outbreak in the U.S. were remote, "we are concerned that even a relatively limited number of cases within the United States could result in harmful disruptions to our economy and society."

Also on Wednesday, the Obama administration briefed House and Senate staffers on the Ebola outbreak and the administration's response. At least 200 people attended a 90-minute meeting in a Senate office building. No lawmakers attended the meeting, which was closed to the press.

"There's a huge amount of interest in Ebola, so getting information out widely is helpful," said Rear Adm. Stephen C. Redd, an assistant surgeon general and spokesman for the Centers for Disease Control and Prevention.

Redd and other CDC officials said the briefings, which included separate sessions for House and Senate staffers, were scheduled after a series of offices began requesting individual briefings on the outbreak. The House Energy and Commerce Committee scheduled a hearing on the outbreak Thursday.

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