Abstract / Summary
Abstract Objective Psittacosis is a zoonotic infectious disease caused by Chlamydia psittaci , with an increasing number of documented clustered outbreaks associated with pet bird exposure. Nevertheless, high-resolution epidemiological data and evidence from laboratory traceability for community clusters of psittacosis remain insufficient in existing research. Methods In January 2026, a cluster of febrile illnesses involving three individuals occurred in Zhoushan City, Zhejiang Province, China. A field epidemiological investigation was conducted, including interviews with cases and close contacts. Clinical and environmental specimens were collected and tested for C. psittaci by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and metagenomic third-generation high-throughput sequencing (TGS). Phylogenetic analysis was performed by comparing nucleotide sequences from clinical and environmental isolates. Results The cluster comprised one laboratory-confirmed case (Patient 1, a 73-year-old male) and two suspected cases (Patients 2 and 3, a married couple aged 78 and 75 years). All three shared a common exposure: Patients 2 and 3 kept parrots at their residence, which also housed a mahjong parlour where Patient 1 spent 3–4 hours daily before symptom onset. Environmental testing revealed C. psittaci nucleic acid positivity rates of 100% (10/10) in samples from the birdcage and master bedroom, and 37.5% (3/8) in samples from the mahjong table area. Traceability investigation of a supplier bird shop showed a positivity rate of 73.3% (11/15). The strain sequence from Patient 1's respiratory specimen differed by 1–2 nucleotides from environmental strains recovered from patients 2 and 3's residence. Conclusion This cluster was primarily driven by infected parrots as the reservoir, with transmission likely occurring through contact with pathogen-carrying birds or inhalation of contaminated aerosols in a shared indoor environment. Human-to-human transmission cannot be ruled out. Strengthened regulation of live bird markets, health education, and improved clinical recognition of psittacosis are recommended.