Significant impact of the Rh blood group and gender on influenza infection in Estonia

To get an insight into the epidemics of influenza caused by the pandemic A(H1N1)pdm09 virus in Estonia, titres of anti-H1N1 antibodies were determined from 530 blood donor sera and from 355 pig sera collected during the second post pandemic year (2010-2011) in Estonia. The results indicate that A(H1N1)pdm09 was well spread among the Estonian population during the second year of spreading. The median antibody titres of A(H1N1)pdm09 were higher in the sample of Estonian men than women, but the reason for this is unclear. The impact of blood group, age, and gender on the titre of anti-H1N1 antibodies in human serum samples was studied. A significant difference was observed between the RhD donor groups: the RhD+ group had a higher antibody titre than the RhD group. A significant influence of the RhCcEc system was observed, the Ccee combination promoting the highest antibody titre. These observations suggest that viral infections might exert substantial pressure on the evolution of human blood groups. Pig serum samples from half of the Estonian pig farms were tested, indicating that the A(H1N1)pdm09 virus had infected animals in two-thirds of the farms. Altogether, our study shows that a virus serologically similar to the A(H1N1)pdm09 virus was prevalent in Estonia in both human and pig populations during 2010-2011, and reveals important factors influencing the serum titre of antibodies to this virus.