The causative factor of Corynebacterium diphtheriae is diphtheria exotoxin, which has strong antigenicity and severe toxicity. K antigen (surface antigen) and cord factors are also related to its pathogenicity. Diphtheria is an acute respiratory infectious disease. The immunity against diphtheria is mainly anti-toxin immunity, which can be detected by intradermal test of diphtheria exotoxin. Corynebacterium diphtheriae can cause diphtheria in humans. Diphtheria is an acute respiratory infectious disease. The pathogenic bacteria exist in the nasopharyngeal cavity of patients and carriers and are spread through droplets or contaminated items. Corynebacterium diphtheriae can cause pseudomembranes in the trachea and bronchus, which is the main cause of death in the early stages of diphtheria. The exotoxins it produces also combine with susceptible tissues through the blood, causing various symptoms, such as myocarditis, soft palate paralysis, etc., which are the main cause of death in the late stages of diphtheria. main reason.