Scientists have made an important discovery about one vicious disease that threatens the lives of millions of people, but what is the sickle cell trait, and why does it have such unusual characteristics? Research published in the New England Journal of Medicine finds that, thankfully, people who have the genetic sickle cell trait aren’t at a higher risk of dying suddenly, but it certainly sheds light on an unusual disease that affects one race disproportionately — and for a fascinating reason.

Sickle cell disease is not exclusive to African-Americans, but they get the majority of cases. About one in every 365 black people born in American get sickle cell disease, which is when they have two copies of a particular gene, and one in 13 have the sickle cell trait, when they have just one copy, according to a Stanford University Medical Center statement.

But just what is sickle cell disease, and why is it so deadly?  Sickle cell is a blood disorder where the blood cell becomes misshapen. It is also called sickle-celled anaemia. It can result in a restriction of blood flow to organs, resulting in pain, necrosis and often organ damage. It can result in chest pain, fever, and hypoxemia. It can result in a fast heart rate, fatigue, and pale appearance. And frequently, it results in death.

So why do those of African descent get it so much more than any other race? The answer is simple. Sickle cell disease evolved as a result of a greater resistance to malaria, and since Africa is smack dab in the “malaria belt” — which includes the Middle East, southern Europe and South Asia — the gene variant flourished due to the benefits of malaria resistance. Sickle cell was simply a side effect.

“The most important thing to come out of this study is the really reassuring news that under conditions of universal precautions against dehydration and overheating, we don’t see an elevation in the risk of mortality in people with sickle cell trait,” Lianne Kurina, PhD, an associate professor of medicine at Stanford, said in the statement.

The statement adds: “Kurina and her colleagues found that the risk of exertional rhabdomyolysis was only 54 percent higher among African-American soldiers with sickle cell trait than among those without it. A 54 percent increase might sound like a lot, but it’s far less than the 300 percent increase caused by some ordinary prescription drugs. And smoking, obesity and increasing age each incur a heightened risk of ER that is about the same as sickle cell trait, the study showed.”