[Significance of persons with different blood groups in the influenza type A epidemic process]

To study the susceptibility of persons with different blood groups to influenza A, the presence of infection in a group of young children placed under constant observation for 6 years (1974-1980) and in a group of donors observed during 1979-1980 was studied in different epidemic situations. The susceptibility of the persons under observation to type A influenza viruses was shown to depend both on the blood group of the subjects and on the properties of circulating viruses. Persons with group B (III) blood were more susceptible to the virus at the period when new antigenic variants and serotypes appeared, persons with group O (I) blood were more susceptible to influenza infection at the period of the circulation of virulent strains, while persons with group A (II) blood were more susceptible at the period when less virulent strains circulated. The susceptibility of persons with different blood groups was found to change as changes in the properties of the strains occurred in the process of their circulation.