Epidemiology, Clinical Features, and Advances in Diagnosis and Treatment of Chlamydia psittaci Pneumonia: A Narrative Review

Chlamydia psittaci pneumonia is an underrecognized zoonotic infectious disease that primarily involves the lungs but frequently affects extrapulmonary organ systems. Clinical and radiological features are nonspecific, and diagnosis remains challenging. Culture, although the gold standard, is slow, low-yield, and requires biosafety level 3 facilities; serology is limited by cross-reactivity and the need for paired sera; and polymerase chain reaction, although rapid, generally targets selected genes and is often used only when clinical suspicion is high. The widespread use of metagenomic next-generation sequencing and targeted next-generation sequencing has increased the reported detection of C. psittaci , largely reflecting improved diagnostic capability rather than a proven increase in disease incidence. Tetracyclines remain first-line therapy; macrolides and fluoroquinolones are alternatives, although fluoroquinolone monotherapy may fail in severe disease. Evidence for combination therapy and newer agents such as omadacycline remains limited, and the true disease burden is likely underestimated because surveillance is incomplete. This narrative review summarizes current evidence on epidemiology, clinical and radiological features, diagnosis, and treatment of C. psittaci pneumonia and highlights key evidence gaps.