As the coronavirus spreads across the country, millions of Americans already struggling with health and finances — especially those in minority communities — could bear the brunt of it.

New data released Tuesday by the show that COVID-19 patients with underlying health issues in the United States are more likely to need treatment in a hospital — or even in an intensive care unit. They are also at higher risk of dying, according to earlier epidemiological data from both China and the U.S.

Because health and wealth in the U.S. are so often linked, the coronavirus could hit low-income populations here much harder, experts say.

The elderly are the hardest hit by the disease, accounting for about 80% of fatal cases in China and the U.S., according to CDC data.

But studies have also shown that underlying health issues such as asthma, diabetes and heart disease can also make COVID-19 more dangerous, as the disease taxes already-burdened organs.

More than a third of American adults — 105 million people — are at higher risk of serious illness if they get infected with the coronavirus, according to a Kaiser Family Foundation analysis of CDC data. For most of them, their age puts them in danger: More than 76 million Americans are 60 or older. The remaining 29 million people are younger but have underlying health issues.

Age and underlying health issues go hand in hand: COVID-19 has so far been most menacing to older people with underlying illnesses. But the disease has already killed younger Americans — for example, a 34-year-old California man who had asthma and a 44-year-old Louisiana woman who had unspecified underlying illnesses.

Weakened already

More than three-quarters of the COVID-19 patients who required ICU treatment in the U.S. had underlying health issues, including heart disease, diabetes and chronic lung conditions, according to the new CDC data on 6,600 cases for which underlying conditions and hospitalization status were reported. Certain underlying conditions were more likely to lead to intensive care in the hospital — for instance, of the COVID-19 patients who had underlying heart disease in that same CDC analysis, 21.5% landed in the ICU.

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Chinese scientists have also reported that heart disease, nearly as much as age, was a reliable indicator of whether a COVID-19 patient would require advanced medical treatment. And COVID-19 patients with underlying conditions in China were also more likely to die. About 10% of Chinese patients with cardiovascular problems died. For diabetes patients, the results were similar: More than 7% died. That's compared with 0.9% of patients with no underlying illness.

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Doctors around the world have also reported that some patients with severe COVID-19 were having heart attacks and other heart complications while hospitalized for the coronavirus, though those reports are still anecdotal.

Other viruses that attack the lungs, such as the flu, also affect the heart, says Dr. R. Scott Stephens, who runs an intensive care unit at Johns Hopkins Hospital in Baltimore. So it makes sense that underlying heart disease would make the coronavirus more dangerous.

"We're thinking about plans for 'How do we screen patients for this? What are interventions that we can use?'" Stephens says. "It's kind of like you're on the beach waiting for the wave to hit. You just don't know when it's going to hit and how big it's going to be."

In the U.S., African Americans are far more likely to have fatal heart conditions than other groups, says Donna Spiegelman, a biostatistician and epidemiologist at the Yale School of Medicine. Researchers worry that this means the U.S. could end up with noticeable disparities in who dies from the coronavirus.

In 2017, the latest year for which data are available, African Americans died from heart disease at a rate of 208 per 100,000, while whites died at a rate of 169 per 100,000. Other racial and ethnic groups' rates were even lower.

"I would expect there would be racial and ethnic disparities simply based on the disease burden that is already present," says Leonard Friedman, a professor of health policy and management at George Washington University.

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The coronavirus could also exacerbate regional disparities, as heart disease takes a greater toll on some areas of the country than others. The map above shows that Appalachia, rural northwest Mississippi and eastern Michigan, including Detroit, are among areas with high percentages of Medicare recipients hospitalized for heart disease.

Low-income health struggles

In the U.S., people who struggle financially often struggle to stay healthy. The coronavirus could attack their lives at all angles, experts say: They are more likely to have underlying health issues, putting them at higher risk of serious complications and death. They are more likely to have jobs that do not allow them to work from home, increasing their likelihood of being exposed to the virus. And they are more likely to be underinsured, potentially keeping them from seeking treatment until it's too late.

"You start with those underlying conditions, and then each layer of this is just going to magnify that further," says Jon Zelner, a University of Michigan epidemiologist. "You may see disparities in who dies and who becomes ill."

During the 1918 Spanish flu pandemic, people who lived in Chicago neighborhoods with low literacy rates were more likely to die than people living in neighborhoods with high literacy rates, according to a 2016 study published by the National Academy of Sciences.

"Whenever there is a disaster," says Pinar Keskinocak, a professor at Georgia Institute of Technology who specializes in infectious disease modeling, "I think unfortunately people with low income and in low-income groups always tend to be the most impacted."

People in rural areas may have to travel farther to reach a doctor or a hospital with a ventilator if they find themselves short of breath with the coronavirus, but they aren't the only ones with barriers to accessing health care. Studies have shown that low-income people in urban areas also struggle to get to their doctor.

"Low-income populations are going to be hit regardless of where they live, rural or urban," says Julie Swann, an industrial engineering professor at North Carolina State University who has helped build models predicting how pandemics could spread. "If someone is not able to get in early enough to get appropriate care, then their situation could escalate, and they could end up in the hospital."

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But rural areas often do have weaker defenses against public health crises. The map above shows places the CDC says are more vulnerable to "stresses on human health" because of a combination of factors — including poverty, education levels, housing quality and other issues like lack of access to transportation.

Counties along the border with Mexico, wide swaths of the South and sparsely populated areas in Alaska stand out as just a few of the places with few tools to fight the coronavirus.

Many rural hospitals have shuttered after years of financial hardship, and the ones that remain open often have small staffs — without the layers of specialized doctors and critical care nurses found at urban hospitals.

"We can only imagine, but you can think about bringing your mother or grandmother to the emergency room and it being literally filled with people and having to wait outside for hours before you're even seen by somebody," says Spiegelman, the Yale epidemiologist. "And maybe even some people would even die while they're waiting."

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