Psittacosis contagion in 1930: an old story in a new era of zoonotic disease

The SARS-CoV-2 pandemic has highlighted the importance of zoonotic diseases. Psittacosis, a human disease resulting from infection spill-over from Chlamydia psittaci-infected birds, is a lesser-known example of a zoonosis. Psittacosis was responsible for numerous outbreaks in the 1930s, characterised by significant human mortality and disruption to the global trade in parrots. This paper describes the epidemiological and clinical details of one family group impacted by the purchase of an infected, imported parrot. Findings are discussed in the context of a growing awareness of the health risks of global disease outbreaks, as well as social and economic impacts. Health information recorded for cases of psittacosis associated with the 1930 cluster was reviewed using contemporary knowledge of disease symptoms and epidemiology. Case details and autopsy reports were examined. Public health investigation deduced that the cluster of infections was chronologically and physically connected to the purchase and subsequent death of an imported parrot. Disease symptoms were consistent with C. psittaci infection. Epidemiological data supported the diagnoses and causes of death, despite the presenting symptoms sharing significant overlap with other common respiratory diseases. There is growing awareness of the risks of epidemiological bridges in transmitting animal diseases to humans. Historical cases are a strong reminder of the fundamental role of scientific and public health responses in the face of such contagion.