Background: Influenza is an acute respiratory illness caused by the Influenza virus. There are 3 types of Influenza virus A, B and C. Infection with the Influenza virus exhibits broad immune responses and protection from re-infection by the same type of virus. The protective humoral immune response depends mainly on antibodies to the virus surface glycoprotein, hemagglutinin, and neuraminidase. Our study aims to reveal the characteristics of hemagglutinin reactive serum antibody responses in influenza patients in Suez Governorate. Methods: 160 cases were enrolled according to their clinical picture and symptoms onset not more than 10 days from the beginning of illness. Nasopharyngeal swabs were obtained from each case and tested for the influenza virus by rapid influenza antigen detection test. The proven influenza A samples were typed by real-time PCR. Each sample was mapped for their hemagglutinin (HA) antibodies rising titer by ELISA: group 1 HAs (H1, H5, H9) and group 2 HAs (H3 and H7). Results: 15 cases were diagnosed as influenza A with subtype H1N1. There was a rise in group 1HAs more than group 2 HAs when comparing the antibody titer of the 1st and 2nd serum samples. Group 1: H1 showed a 20-fold rise, H5 showed a 5-fold rise and H9 showed a 2-fold rise. Group 2: H3 and H9 showed a 5-fold rise. Conclusion: Following natural infection; Influenza A(H1N1) pdm09 virus induces a strong anti-HA immune response.