Coxiella burnetii and Q Fever in Portugal: A Systematic Review Under a One Health Perspective

Q fever, caused by Coxiella burnetii, is a globally distributed zoonotic disease with significant public health and veterinary relevance, yet its epidemiology in Portugal remains fragmented. This systematic review aimed to assess the epidemiology of C. burnetii infection and Q fever in Portugal by compiling, critically analysing and integrating available evidence from animal, human, and environmental studies, adopting a One Health perspective. A comprehensive literature search was conducted in international databases and national repositories in accordance with PRISMA 2020 guidelines. Studies reporting serological, molecular or isolation-based detection of C. burnetii in humans, animals or environmental samples were eligible. A total of 24 studies were included, covering human populations, ruminants, companion animals, wildlife and environmental matrices. Evidence was predominantly focused on ruminants, with consistently high and heterogeneous levels of exposure reported across different species, regions and production systems. Human epidemiological studies were limited and largely restricted to occupational groups and blood donors, but consistently indicated substantial exposure, suggesting underdiagnosis and underreporting. Data on companion animals, wildlife and environmental sources were scarce and methodologically heterogeneous. This review confirms endemic circulation of C. burnetii in Portugal, but highlights pronounced geographic and methodological gaps, reinforcing the need for harmonised, integrated One Health surveillance to improve risk assessment and evidence-based prevention strategies.