Antibodies of influenza viruses in military recruits from Argentina, Brazil and Colombia. Their relation to ABO blood group distribution.

In a large-scale seroepidemiological study, the prevalence was determined of antibodies to influenza A viruses in the sera of military representative of the inhabited geographical regions of Argentina, Brazil and Colombia. The micro-haemagglutination-inhibition test was used against the Swine, PR/8, FM/1 and Asian antigenic strains. From each of the three recruit populations 500 sera were tested.Positive titres to the FM/1 and Asian strains were found in 72% and 80% respectively of the Colombian sera, in 56% and 69% of the Argentinian sera, and in 49% and 63% of the Brazilian sera. Of these 1500 sera, 5 were positive to the PR/8 strain and 2 to the Swine strain.This study also showed that there were highly significantly greater proportions of positive reactors to the FM/1 and Asian strains among persons of blood groups O and B than among those of blood group A in all three countries.