ABO blood groups and viral diseases.

Tlhe role of ABO blood groups in differential susceptibility to various diseases lhas lonig been a subject of investigation ani(1 debate(1). The genetic factors involve(l in resistanice against Virus infectionis lhave been reviewed by Allison(2). In the l)ast few years tlhree reports l)y Englislh writers lhave claimed to slhow a hiiglher susceptibility of persons of )loo0( grotup 0 to influenza than otlher blood groups. In 1962 'McDoniald and Ztuckerman analyzedl the dlistribution of blood groups among 2000 serologically conifiirmed respiratory illnesses in Royal Air Force personinel from 195(6 to 1961 as comipared to their distribution in a control group of about 50,000 RAF recruiits wlhose blood0 grotups were known(3). A statistically significant excess of Grotp 0 p)atienlts was foulnd( among those witlh illness due to A2 influeniza but not among those witlh illniesses dute to influenza Al or B or to Coxsackie A21. An opposite trend was seen for certain adlenovirus infections. In 1968 Potter andl Schild(4) tested the prevalence of antibody to the A2/Singapore strain of influenza in the sera of 515 persons of different ages collectedl from 1961 to 1963. A hiiglerl prevalence of this antibody in persons of group 0 b)lood was ob)serve(l in all age groups but in only two age groups, age 16 to 20 and over 30-years-old, was this relationslhip significant by the X2 test. In a third sttldy by Tyrell, Sparrow, an(d Bear publislhecl in 1968(5) the role of ABO stus-