Dr. Anthony Fauci, a member of the White House coronavirus task force, said Sunday that “community spread” cases of the virus, which cannot be directly traced to anyone, are becoming more prevalent in the United States.

The term “community spread” is used when a person becomes infected with no known original source or index case, in contrast to earlier travel-related cases which were clearer in how and where the infections originated, Fauci told “Fox & Friends Weekend” in a Sunday morning interview.

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While this makes it more challenging for officials to trace a point of origin for the infectious disease and contain it, Fauci said the development did not come as a surprise to health officials.

“This was something that was entirely expected when you have diffuse infections throughout the world – as you’ve just mentioned, South Korea, Iran, Italy, in places like that – sooner or later there are going to be cases in your country that you can’t directly trace to anyone,” Fauci said. “That becomes much more challenging about identifying the source.”

These types of cases, which have been reported in Washington state and Oregon, require officials to do “much more intensive contact tracing in addition to the isolation,” he said.

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Fauci, who is also director of the National Institute of Allergy and Infectious Diseases, went on to address whether it is appropriate to compare the coronavirus with the seasonal flu.

“Yes and no,” Fauci said, cautioning that the comparison is suitable in some respects, but not in others.

“It clearly is much more lethal, if you want to call it that, than the typical seasonal flu,” he said.

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The seasonal flu mortality rate is about 0.1 percent, while information thus far, particularly from China, indicates the coronavirus mortality rate is around 2 to 2.3 percent, Fauci said, adding that the number might be a little lower if all cases around the world were counted.

He said that like the flu, coronavirus will most commonly afflict older people with underlying health problems, while infections in young, healthy individuals can still occur, although be more unusual.

In a projection of the outbreak in the coming weeks, Fauci said “the American people really need to realize” that more cases will pop up in communities in which there is no identified source.

“It’s unrealistic to think it’s not going to happen,” Fauci said. “It is how we handle it that’s important.”

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The viral outbreak began in China and has infected more than 87,000 people globally and caused nearly 3,000 deaths. According to the Associated Press, there have been 72 cases in the U.S. and one fatality.

On Sunday, Health and Human Services Secretary Alex Azar said that a new case of the coronavirus appeared in Chicago overnight. A day earlier, officials confirmed the first virus-related fatality in the U.S. occurred in Washington state.