People in Africa who become critically ill from Covid-19 are more likely to die than patients in other parts of the world, according to a report published on Thursday in the medical journal The Lancet.

The report, based on data from 64 hospitals in 10 countries, is the first broad look at what happens to critically ill Covid patients in Africa, the authors say.

The increased risk of death applies only to those who become severely ill, not to everyone who catches the disease. Over all, the rates of illness and death from Covid in Africa appear lower than in the rest of the world. But if the virus begins to spread more rapidly in Africa, as it has in other regions, these findings suggest that the death toll could worsen.

Among 3,077 critically ill patients admitted to the African hospitals, 48.2 percent died within 30 days, compared with a global average of 31.5 percent, the Lancet study found.

The study was observational, meaning that the researchers followed the patients’ progress, but did not experiment with treatments. The work was done by a large team called The African Covid-19 Critical Care Outcomes Study Investigators.

For Africa as a whole, the death rate among severely ill Covid patients may be even higher than it was in the study, the researchers said, because much of their information came from relatively well-equipped hospitals, and 36 percent of those facilities were in South Africa and Egypt, which have better resources than many other African countries. In addition, the patients in the study, with an average age of 56, were younger than many other critically ill Covid patients, indicating that death rates outside the study could be higher.

The other eight countries in the study were Ethiopia, Ghana, Kenya, Libya, Malawi, Mozambique, Niger and Nigeria. Leaders of 16 other African nations had also agreed to participate, but ultimately did not.

Reasons for the higher death rates include a lack of resources such as surge capacity in intensive care units, equipment to measure patients’ oxygen levels, dialysis machines and so-called ECMO devices to pump oxygen into the bloodstream of patients whose lungs become so impaired that even a ventilator is not enough to keep them alive.

But there was also an apparent failure to use resources that were available, the authors of the study suggested. Proning — turning patients onto their stomachs to help them breathe — was underused, performed for only about a sixth of the patients who needed it.

Almost 16 percent of the hospitals had ECMO, but it was offered to less than 1 percent of patients. Similarly, although 68 percent of the sites had access to dialysis to treat kidney failure, which is common in severe Covid cases, only 10 percent of the critically ill patients received it. Half the patients who died were never given oxygen, but the authors of the study said they had little data to explain why.

A Lancet editorial by experts not involved in the study said, “It is common in Africa to have expensive equipment that is non-functional due to poor maintenance or lack of skilled human resources.” Some 40 percent of the medical equipment in Africa was out of service, according to a 2017 report by the Tropical Health and Education Trust, the editorial said.

Another factor is that few doctors in Africa have the training in pulmonary and critical care that is considered essential in treating Covid patients.

As in other studies, chronic conditions like diabetes, high blood pressure, and diseases affecting the heart, kidney or liver increased the risk of death from Covid. This study was the first to include a large proportion of patients with H.I.V., which nearly doubled the risk of death. The report states, “Our data suggests that H.I.V./AIDS is an important risk factor for Covid-19 mortality.” But the authors also said they did not have data on how the severity of the H.I.V. infection might affect the risk.

An unexpected finding of the study was that, unlike Covid patients in the rest of the world, men in Africa were no more likely than women to die. That result suggests that African women are at higher risk than women in other regions.

The authors suggested that women in Africa might face “barriers to accessing care and limitations or biases in care when critically ill.”

The editorial asked whether new variants could be causing the high death rate found in the study, but also said, “This is a question which, in a continent with severe shortage of sequencing, could take a long time to answer.”