Legionella pneumophila is a flagella, gram-negative, Legionella polymorphic brecobacterium.

The invasion of Legionella pneumophila to the human body is mainly manifested as Legionella pneumonia, which is a kind of atypical pneumonia group, which mostly occurs in summer and autumn, and sporadic cases occur throughout the year. Pathogenic bacteria can spread with water mist, and people may become infected once inhaled. Among them, the elderly, pregnant women and children, as well as people with chronic diseases and immunocompromised people are more susceptible to the disease.