Epidemiology

Infection occurs sporadically or as outbreaks. Outbreaks are more common among workers on duck or poultry farms, and in abattoirs and processing plants.[5][6]

Between 25 and 50 cases are confirmed in England and Wales each year.[7] There have typically been fewer than 10 confirmed cases reported in the US each year since 2010, with 5 cases reported in 2017.[8] An outbreak was reported among workers at two poultry slaughter plants in Virginia and Georgia during August to October 2018 (13 confirmed cases).[9]

One meta-analysis found that approximately 1% of cases of community-acquired pneumonia were due to Chlamydia psittaci, with a range between 0% and 6.7%.[10] A Dutch study identified C psittaci by polymerase chain reaction of sputum as a cause of community-acquired pneumonia in 4.8% of cases.[11]Reporting may be limited by the fact that clinical differentiation of illness caused by C psittaci and illness caused by other organisms, especially Chlamydophila pneumoniae, can be difficult.

Approximately 5% to 8% of birds are infected withC psittaci, and 465 avian species are susceptible to this organism, most commonly psittacine (parrot-type) birds, especially budgerigars and cockatiels.[1][12]C psittaci strains that infect psittacine birds and poultry are more virulent and can infect humans of all age groups through aerosolised particles or direct contact with infected nasal secretions, faeces, or tissue.[1][6]

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