Molecular detection of Coxiella burnetii in suspected dengue patients from the Bauru region, São Paulo State, Brazil.
Q fever, caused by Coxiella burnetii, is an underdiagnosed zoonosis in Brazil due to its non-specific clinical presentation and limited diagnostic capacity. This study investigated the molecular detection of C. burnetii in serum samples from patients with acute febrile illness initially suspected of dengue in 34 municipalities of São Paulo State, Brazil. A total of 300 serum samples collected over a three-year period from patients with suspected dengue fever were analyzed. Only samples obtained from patients presenting with up to seven days of febrile illness were included. All samples tested negative for dengue, leptospirosis, and brucellosis and were analyzed by real-time PCR targeting the IS1111 gene. C. burnetii DNA was detected in 1.3% (4/300) of the samples (95%CI: 0.37%-3.35%), compatible with recent infection during the early symptomatic phase. This study represents the second report of molecular detection of C. burnetii in patients with acute febrile syndrome in Brazil and the first one in São Paulo State. Previous serological studies indicate widespread exposure to the pathogen, highlighting the complementary roles of molecular and serological approaches. These findings support the inclusion of Q fever in the differential diagnosis of undifferentiated febrile illnesses and suggest that One Health-oriented surveillance strategies may help reduce underdiagnosis in Brazil, although further studies with larger sample sizes are needed to confirm this recommendation.