Sickle cell disease can affect anyone, but it overwhelmingly occurs in people whose ancestors came from regions where malaria was historically common. That includes sub-Saharan Africa, the Mediterranean, the Middle East, India, and parts of Central and South America. Globally, an estimated 7.74 million people live with sickle cell disease, and roughly 515,000 babies are born with it each year.
How Sickle Cell Is Inherited
Sickle cell disease is a genetic condition, not something you can catch or develop on your own. To be born with it, a child must inherit a faulty hemoglobin gene from both parents. The most common form happens when both parents pass on a gene for hemoglobin S, the variant that causes red blood cells to deform into a rigid, crescent shape. But sickle cell disease can also result from inheriting one hemoglobin S gene and one gene for a different hemoglobin abnormality, such as beta thalassemia or hemoglobin C.
When both parents carry the sickle cell trait (meaning each has one normal gene and one hemoglobin S gene), every pregnancy carries a 25% chance the child will have sickle cell disease, a 50% chance the child will carry the trait without having the disease, and a 25% chance the child will inherit two normal genes. Carriers with the trait typically live without symptoms and may not know they carry the gene at all.
Populations Most Affected
In the United States, more than 90% of people with sickle cell disease are non-Hispanic Black or African American. The condition occurs in about 1 out of every 365 Black newborns, based on recent CDC data covering 2016 to 2020. Hispanic Americans are the next most affected group, with sickle cell disease occurring in roughly 1 out of every 16,300 Hispanic births. An estimated 3% to 9% of Americans living with sickle cell disease are Hispanic or Latino.
But sickle cell is not exclusive to any single race or ethnicity. It affects people of Mediterranean descent, including families with roots in Greece, Italy, and Turkey. In Greece, for example, about 8% of the general population carries a variant of the hemoglobin gene. People from Saudi Arabia, India, and the Caribbean also carry the gene at significant rates. Nearly 80% of global cases are concentrated in sub-Saharan Africa, where the gene is most prevalent.
Why Certain Populations Carry the Gene
The sickle cell gene persists in these populations because carrying one copy of it offers a survival advantage against malaria. The malaria parasite invades red blood cells to reproduce, but it has a much harder time thriving in cells that contain hemoglobin S. When the parasite does infect a carrier’s red blood cells, those cells tend to sickle more readily than uninfected ones, which flags them for removal by the body’s immune system before the parasite can spread.
Hemoglobin S is also less chemically stable than normal hemoglobin. It releases free heme faster, and the body responds by producing an enzyme that breaks heme down into carbon monoxide and other byproducts. That carbon monoxide actually helps prevent the severe brain complications that make malaria deadly. So in regions where malaria killed large numbers of children, people who carried one copy of the sickle cell gene were more likely to survive to adulthood and pass on their genes. Over thousands of years, this kept the gene common in malaria-endemic areas.
This is why the geographic footprint of sickle cell maps so closely onto historical malaria zones: tropical and subtropical Africa, the Mediterranean coast, the Arabian Peninsula, and the Indian subcontinent.
Sickle Cell Trait vs. Sickle Cell Disease
There’s an important distinction between carrying the trait and having the disease. People with sickle cell trait have one normal hemoglobin gene and one hemoglobin S gene. They produce enough normal hemoglobin that their red blood cells function well under ordinary conditions. Most carriers never experience symptoms and live entirely normal lives. They can, however, pass the gene to their children.
People with sickle cell disease have two abnormal hemoglobin genes. Their red blood cells frequently become rigid and crescent-shaped, which causes them to clump together and block small blood vessels. This leads to episodes of intense pain, chronic damage to organs like the heart and kidneys, and an increased risk of silent strokes, which are areas of brain damage that occur without obvious external symptoms. The disease requires lifelong medical management.
How Sickle Cell Is Detected
In the United States, every newborn is screened for sickle cell disease at birth through a routine blood test. This has been universal across all 50 states since 2006. The screening uses a method called hemoglobin electrophoresis, which separates the different types of hemoglobin in a blood sample to identify whether a baby has normal hemoglobin, the sickle cell trait, or sickle cell disease. Results are typically compared with a complete blood count and a blood smear for confirmation.
Adults who were not screened at birth, or who want to know their carrier status before having children, can request the same blood test. This is particularly relevant for anyone with ancestry from high-prevalence regions. Knowing your carrier status before starting a family lets you understand the chances of passing the gene to your children, especially if your partner also carries a hemoglobin variant.
Can People of Any Race Get Sickle Cell?
Yes. While the gene is far more common in certain populations, sickle cell disease does not follow strict racial boundaries. Migration, intermarriage, and the wide geographic spread of the original gene mean that people of many ethnic backgrounds can carry hemoglobin S. In the U.S., the strong association with Black Americans reflects both the high prevalence of the gene in West African populations and the history of the transatlantic slave trade, but it has always been present in Mediterranean, Middle Eastern, South Asian, and Latin American communities as well.
The misconception that sickle cell is exclusively a “Black disease” has real consequences. It can lead to delayed diagnosis in non-Black patients and gaps in carrier screening for people who don’t fit the expected demographic profile. The gene doesn’t check ancestry records. Anyone whose family tree traces back to a malaria-endemic region could carry it.