First case of Ebola confirmed in the United States: CDC

The United States now has one confirmed case of Ebola, the Centers for Disease Control and Prevention said, marking the first domestic appearance of the deadly virus that has ravaged swaths of continental Africa.

The Ebola epidemic has overwhelmed public health workers in three African countries, one of which was the likely site of infection of the first American case. At least for now, the incident remains isolated. However, CDC officials say the virus incubated here in the U.S. for at least a few days, and others have been exposed.

The as-yet unidentified patient is located in Dallas's Texas Health Presbyterian Hospital. Texas Gov. Rick Perry says a handful of school-aged children who had contact with the man are being monitored.

In a press conference on Tuesday, CDC Director Tom Frieden said the patient in question was traveling through Liberia, where he may have contracted the disease. He entered the United States on the 20th of September, after which he sought care. Reports surfaced that the man is a Liberian national in the U.S. visiting relatives.

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"There may be a small outbreak because he did walk around with symptoms," said Debra Spicehandler, an infectious disease expert at Northern Westchester Hospital in Mount Kisco, NY. "So we may see a few more cases related to him."

On Wednesday, Texas health professionals were monitoring a clutch of potential citizens that may have come into contact with the hospitalized victim. Zachary Thompson, director of Dallas County Health and Human Services, told a local station that there might well be "another case that is a close associate with this particular patient."

Frieden attempted to assuage concerns about Ebola's contagious effect, saying that the virus was only spread through direct contact, and was not airborne. He vowed that officials would contain a potential spread.

Frieden added that "there is no doubt in my mind that we will stop it here," Frieden said.

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In response to a question, Frieden added that "a handful" of people, including family members, may have been exposed to the patient prior to his seeking treatment.

In early September, four U.S. aid workers treating the outbreak in Africa were diagnosed there, and transported back to the U.S. for treatment after falling ill. This case, however, is the first known in which a person was stricken by the virus and diagnosed domestically.

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The recent outbreak is widely considered by experts to be the deadliest in history. In recent days, global health professionals have warned that the strain of Ebola was becoming more virulent, and that governments around the world needed to step up their response. The World Health Organization has estimated that at least 3,000 have died since the first outbreak was identified in Guinea six months ago, and more than 6,500 cases have been confirmed.

Although officials are urging calm, saying the Ebola threat is well-contained for now, at least a few insist the public to be prepared for the worst. One sign of optimism came from Nigeria, where public health professionals appeared to beat back a potentially deadly outbreak of the virus.

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Last week, the head of Doctors Without Borders told the United Nations that the virus "is winning." Separately, the CDC warned that between 550,000 and 1.4 million people in West Africa could be infected with Ebola by January 2015. Sierra Leone, Liberia and Guinea are among the countries most badly affected by the virus.

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News of the virus' appearance sent the share prices of key biotechnology and pharmaceutical companies skyrocketing, but the broader market suffered on increased risk aversion stemming from fears of Ebola's potential spread. In trading on Wall Street on Wednesday, major benchmarks tumbled by more than a percent.

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--CNBC's Everett Rosenfeld contributed to this report.