Officials in Texas today announced that a second health care worker who treated the first person diagnosed with Ebola in the US has tested positive for the deadly disease. In a statement released early Wednesday morning, the Texas Department of State Health Services said that the worker "reported a fever Tuesday and was immediately isolated" at Texas Health Presbyterian Hospital in Dallas. Today's announcement comes after another nurse at the same hospital was diagnosed with Ebola, which marked the first known transmission of the disease in the US. Both workers were providing care for Thomas Duncan, who died from Ebola after returning to the US from a trip to Liberia.

Officials said yesterday that the first health care worker, 26-year-old Nina Pham, is receiving treatment and in good condition, though it remains unclear how she contracted the disease, which spreads through direct contact with the body fluids of an infected patient. The second worker, who has not been named, has been interviewed to identify any others who may have been exposed, and those people will be monitored.

"it is certainly very concerning."

In a statement issued today, the Center for Disease Control and Prevention (CDC) described the second diagnosis as a "serious concern" and said that confirmation testing is underway at its laboratories.

"As we have said before, because of our ongoing investigation, it is not unexpected that there would be additional exposures," the agency said.

Tom Frieden, director of the CDC, said earlier this week that the diagnosis of the first health care worker suggested a clear "breach in protocol."

"It is certainly very concerning, and it tells us that there is a need to enhance the training and protocols and to make sure that the protocols are followed," Frieden said in a press conference Sunday. "The protocols work. We have decades of experience caring for patients with Ebola, but we know that even a single lapse or breach … can result in infection."

Update, 8:24AM ET: Daniel Varga, Chief Clinical Officer at Texas Health Presbyterian Hospital, inadvertently admitted during a news conference this morning that the latest health care worker to become infected with Ebola is a woman. Officials have not revealed her identity or what position she holds at the hospital, however.

Varga also said that his hospital could have done things differently, but failed to explain how two hospital employees contracted Ebola. "We are looking at every element of our personal protective equipment. We don't have an answer for this right now, but we are looking at every angle," he said. "No one wants to get things right more than our hospital."

Update, 9:43AM ET: The CDC has announced stricter equipment guidelines for health professionals treating Ebola patients. According to Bloomberg, Workers at the Texas Health Presbyterian Hospital must now wear hoods that will cover their necks. They must also make sure they wash their hands in a specific sequence. These measures are reminiscent of those enforced by Doctors Without Borders, which requires its workers to don equipment that doesn't leave skin exposed. But the CDC's newest guidelines still differ from those imposed by Doctors Without Borders, as the US agency requires that its workers wear a single pair of gloves. Doctors Without Borders asks for two. Doubling up on gloves, explained CDC direct Tom Frieden earlier this week poses a risk because the practice makes gloves harder to remove.

Update, 11:28AM ET: The CDC is reporting that the second health care worker took a flight on Monday, the day before she began showing Ebola symptoms. The agency is reaching out to all 132 passengers who were on board Frontier Airlines flight 1143 Cleveland to Dallas/Fort Worth, and in a statement, wrote, "Individuals who are determined to be at any potential risk will be actively monitored." Frontier Airlines says it has taken the plane out of service and is helping the CDC determine who was on board.