ABO blood group system group. Compared to O group individuals, non-O group (A, AB, and B) individuals have a 14% reduced risk of squamous cell carcinoma and 4% reduced risk of basal cell carcinoma. Conversely, type O blood is associated with a reduced risk of pancreatic cancer. The B antigen links with increased risk of ovarian cancer. Gastric cancer has reported to be more common in blood group A and least in group O. According to Glass, Holmgren, et al., those in the O blood group have an increased risk of infection with cholera, and those O-group individuals who are infected have more severe
Rh blood group system factor is not identical to the rhesus monkey factor; but by then, "Rhesus Group" and like terms were already in widespread, worldwide use. Thus, notwithstanding it is a misnomer, the term survives (e.g. "rhesus blood group system", and the obsolete terms "rhesus factor", " rhesus positive", and "rhesus negative" - all three which actually refer specifically and "only" to the Rh D factor; and, thus, are misleading when unmodified). Contemporary practice is to use "Rh" as a term of art instead of "Rhesus"; viz. "Rh Group," "Rh factors," "Rh D," etc. The first rhesus blood type was discovered in 1937