What is the difference between sickle cell trait & sickle cell disease?

Carrier vs. Affected: Sickle cell trait denotes being a carrier while sickle cell disease is someone who has the disorder. Sickling requires 2 genes. A person with the s gene and a normal gene would be a carrier and considered to have sickle cell trait. Someone who has s and s would be considered to have sickle cell disease and would likley be affected.