Smallpox frequency and severity in relation to A, B and O blood groups.

The results of routine determination of the blood group of smallpox patients admitted to a Madras hospital over a six-month period suggest that the distribution of blood groups among such patients and the severity of illness among patients of various blood groups do not support the hypothesis that susceptibility or resistance to this disease is associated in any direct way with the possession of A or B blood group substances or antibodies to them. The results reported and other considerations discussed make it improbable that the distribution of blood groups among the population of South India has been influenced by the endemic prevalence of smallpox in that part of the world.