Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 40 1 2011 03 15 107 114 HR Honarmand SS Eshraghi 2015 10 03 Background: This study is performed to reveal most common species and subspecies of leptospires that are main causes of hu­man leptospirosis in Guilan, Northern Province of Iran. Methods: We performed IgM-ELISA and MAT on 282 blood samples from patients who attended to 3 hospitals in the flat area of Guilan Province with clinical symptoms consisted with leptospirosis.  All specimens with titers ≥ 160 against at least one pathogenic strain in MAT and with titers ≥160 in IgM-ELISA were regarded confirmed positive cases indicative acute dis­ease. For any confirmed positive cases, we determined the strains, which had the highest titer to determine the frequency of most common serovars and serogroups.  Results: Seventy of 282 sera had titers ≥160 against at least one pathogenic strain in MAT and titers ≥ 160 in IgM-ELISA. We determined frequency of common causative serogroups which had highest titers in 70 positive cases and only cases which had high titers in MAT and in IgM-ELISA were selected which is a reliable criterion to detect acute disease and to deter­mine causative serogroup. Conclusion: Nine serogroups including sejroe, grippotyphosa, mini, ictero haemorrhagiae, celledoni, autumnalis, cynopteri, pomona, and javanica were more responsible of acute leptospirosis in Guilan. https://ijph.tums.ac.ir/index.php/ijph/article/view/3073 https://ijph.tums.ac.ir/index.php/ijph/article/download/3073/2872