As the coronavirus spread across the United States, sweeping through low-income, densely populated communities, black and Hispanic patients died at higher rates than white patients.

Crowded living conditions, poorer overall health and limited access to care have been blamed, among other factors. But a new study suggests that the disparity was particularly acute for black patients.

Among those seeking medical care for COVID-19, the illness caused by the coronavirus, black patients were hospitalized at nearly three times the rate of white and Hispanic patients, according to an analysis of patient records from a large health care system in Northern California.

The disparity remained even after researchers took into account differences in age, sex, income and the prevalence of chronic health problems that exacerbate COVID-19, like hypertension and Type 2 diabetes.

The finding suggests that black patients may have had limited access to medical care or that they postponed seeking help until later in the course of their illness, when the disease was more advanced.

Black patients were also far less likely than white, Hispanic or Asian patients to have been tested for the virus before going to the emergency room for care.

Black patients “are coming to us later and sicker, and they’re accessing our care through the emergency department and acute care environment,” said Dr. Stephen Lockhart, the chief medical officer at Sutter Health in Sacramento and one of the authors of the new study.

The study, which was peer reviewed, was published in Health Affairs.

Delayed care may give the virus more time to spread through households and neighborhoods, Lockhart and his colleagues concluded. The delays also suggest that minority patients continue to face barriers despite California’s broad expansion of health insurance under the Affordable Care Act.

“How soon you access care, even supportive care, affects how you experience illness and how much pain and suffering you have,” said Kristen Azar, a research scientist at Sutter Health who was the study’s lead author.