People are still dying from a brain disease that they got from contaminated growth hormone treatments they took during the 1950s through 1980s, says a new study. Although doctors stopped using the contaminated hormones decades ago, they are still seeing new cases of the disease today, up to 40 years later, according to Live Science.

Creutzfeldt-Jakob disease (CJD) is a fatal, degenerative brain disease that is usually caused by eating infected beef. In this case, however, the growth hormone was taken from infected human cadavers and was given to children who were deficient in growth hormone.

The study investigated 22 new cases of CJD diagnosed in the United Kingdom between 2003 and 2014. All of the people had received human growth hormone as children before the danger of CJD was discovered, and they began to show symptoms of CJD up to 40 years after receiving the hormone.

Researchers believe patients with certain genes were more at risk of developing the CJD, and specific genes determined whether the disease would develop earlier or later in life.

The study indicates that doctors in the U.K. may see more cases of mad cow disease, known as variant Creutzfeldt-Jakob disease (vCJD) in coming years due to an outbreak in the 1980s and 1990s caused by eating contaminated beef.

A 2013 study published in the British Medical Journal estimated that 1 in 2,000 people in the United Kingdom may carry the infectious protein that causes vCJD.

"We know that prion diseases can have an enormously long incubation period," Dr. Peter Rudge, a co-author of the new study, told Live Science, adding, "There is a risk that a second epidemic of vCJD could occur.

"Ultimately, the disease will die out, but it is impossible to predict when."

The study was published in the journal Brain.