When the coronavirus first began spreading in Philadelphia, it primarily was detected among white people, the limited data available to the city indicate. But over time, the demographics shifted, and new cases are predominantly among African Americans, raising fears that existing inequalities in the city will be exacerbated by the public health crisis.

“This virus does not discriminate," Health Commissioner Thomas Farley said at a news conference this week. "The virus is in every neighborhood. It’s in every population. Everyone needs to take our recommendations seriously to avoid getting the infection or passing on the infection.”

The emerging trend in Philadelphia mirrors other U.S. cities and deepens experts’ fears of a scenario that has played out in past epidemics, in which a virus spread around the globe by those with the means to travel comes down hardest on the most vulnerable communities.

“One of the few constants of social science is that all illness impacts poor people more harshly," St. Joseph’s University sociologist Maria Kefalas said. “The initial hot spot was Montgomery County, where you have lots of travel and people who are very affluent, and a couple weeks ago, the question was: Is this going to be an elite disease?"

The answer to that question is likely to be no, she said, because higher poverty rates among racial minorities in the Philadelphia region make social distancing more difficult and quality health care less accessible.

Fewer people in poor neighborhoods have jobs that enable them to work from home. Also, multigenerational families living together in more crowded homes and apartments could be ripe for spreading the virus. Further, fewer people have the savings to stock up on food and supplies, requiring more trips out of the house.

“Many of the inequalities that existed before … primed us for being candidates to be more exposed,” said Rodney Muhammad, president of the Philadelphia chapter of the NAACP. “When you’re living on the margins, you’re an easy candidate for exposure.”

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Existing inequalities may translate into not just higher rates of infection, but also worse outcomes among those infected. For instance, the legacy of environmental racism, in which disadvantaged communities are likely to be nearer to sources of pollution, can lead to higher rates of chronic diseases like asthma. Diabetes, high blood pressure, and heart disease — which new coronavirus research indicates make people more susceptible to developing serious infections — are more common among African Americans.

“These things have come to a head. It’s an unfortunate perfect storm of negligence that has gone on through generations," City Councilmember Cindy Bass said.

The outbreak in Philadelphia is still in its early stages, but the pattern of racial minorities being disproportionately affected is playing out in other cities where the virus has spread. In Detroit, the mortality rate among black people appears disproportionately high. And in New York, the neighborhoods where the virus is threatening to overwhelm the health-care system are predominantly minority communities.

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On Wednesday, the available data on the race of nearly one-third of the 1,675 confirmed coronavirus patients in the city showed 46% were African American, 37% were white, 10% Latino, and 3% Asian American, Farley said.

Those proportions largely mirror the demographics of the city, indicating the initial overrepresentation of white people among those who tested positive has been erased by higher rates of racial minorities.

By Friday, African American residents made up 50% of the confirmed cases for which race was known, and white people accounted for 33%.

Already, some of the city’s poorer neighborhoods, such as Kingsessing, Nicetown, and parts of Kensington, have high numbers of cases, and nearly one of four people tested were positive for COVID-19.

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Hospitals, clinics, and private labs report coronavirus test results to the city health department, but most of the private labs do not include data on race; the city cautioned against drawing detailed conclusions with the available information.

“The first wave of this epidemic in Philadelphia tended to be with people who traveled other places," Farley said. “Now this is clearly circulating within the city of Philadelphia."

Bass said one factor fueling the spread of the virus among African Americans may have been misinformation that circulated online earlier this year that indicated, falsely, that black people were immune to it.

“Because initially it was concentrated in the other communities, Asians and Caucasians, people didn’t see it as a threat to the African American community,” Bass said. "Now we’re playing catch-up with the messaging and spreading the word that it can affect any one of us.”

Concerned about the city’s social distancing guidelines not reaching every neighborhood, Council members say they need to launch their own messaging campaigns. While taking up an $85 million emergency funding bill approved this week at the request of Mayor Jim Kenney’s administration, Council added a provision that would direct $400,000 to its own budget for communications expenses.

Council President Darrell L. Clarke said district Council members are sometimes better suited to reach vulnerable populations that aren’t being reached by the city.

“We know that the spread of the COVID-19 coronavirus is increasing in communities of color, based on the initial data released by the health department," Clarke said in a statement. "City Council intends to reach people in a variety of ways in the time ahead with a clear message: Stay at home, save lives, help flatten the curve.”

Correction: An earlier version of this story misspelled the name of St. Joseph’s University sociologist Maria Kefalas.