Survivors of Ebola virus disease have a higher than normal risk of dying within a year of leaving the hospital, most likely from kidney damage. This information comes from a study of survivors of Ebola in Guinea.

Researchers followed more than 1,100 people who were infected with the virus and survived. They found that their death rates a year after leaving hospitals were up to five times higher than the number expected in Guinea's normal population.

Ebola infected 28,000 people across West Africa between 2013 and 2016. More than 11,300 of them died from the disease.

Death rates were higher among those who were in the hospital for longer periods, the study found. This suggests that patients who had the most severe cases of Ebola may have a higher risk for death after they were treated.

The researchers say the findings show an urgent need for more investigation of the long-term effects of Ebola infection. They noted that the number of Ebola survivors has risen sharply after two large epidemics in the past five years.

The current Ebola outbreak in Democratic Republic of Congo is now the world's second largest in history. The first infection was reported in August of 2018. The disease has spread and infected nearly 3,000 people in the DRC, killing more than 60 percent.

Ibrahima Socé Fall is an emergency medicine expert with the World Health Organization. He and a team of scientists led the latest study. They followed 1,130 Ebola survivors of the 2013-2016 outbreak in Guinea. During the two years that followed their stay in the hospital, 59 survivors died.

After listening to family members describe problems that led to the deaths, the researchers believe that about 37 of the patients died as a result of renal failure.

A report on the study appeared earlier this month in the publication Lancet Infectious Diseases.

Scientists said it was not possible to give the exact cause or date of death for many patients. There were few medical documents available. But studies have found that the virus can be found in patients' liquid wastes, which means the kidneys are infected. Some patients with Ebola develop a serious kidney injury.

"Evidence was weak for most patients, (but) renal failure is a biologically (possible) cause of death in survivors of Ebola virus disease," said Mory Keita, a medical doctor.

Keita, a disease expert from Guinea, is now working with the WHO to help control the Congo Ebola outbreak.

Judith Glynn is with the London School of Hygiene & Tropical Medicine. She also worked on the research team.

Glynn said the report's findings should help emergency care experts direct more resources on higher-risk groups. "Those hospitalized with Ebola for longer may be at greater risk, and could be...targeted," she said.

I'm Susan Shand.

The Reuters News Agency reported this story. Susan Shand adapted it for VOA Learning English. George Grow was the editor.