Unravelling a new focus of spotted fever rickettsioses as causative agents of acute undifferentiated febrile illness in Odisha, a state in eastern coastal India.

Spotted fever group Rickettsia (SFGR) infections remain largely under-investigated as causative agents of acute undifferentiated febrile illness (AUFI) in resource-limited settings. Few studies are available on the prevalence of SFGR infections in India, especially in eastern India. In a cross-sectional study conducted in 192 hospitalized adult and paediatric patients with AUFI, the frequency of SFGR using sequential PCR targeting genes encoding citrate synthase (gltA), 17 kDa lipoprotein precursor antigen (17kDa), outer membrane proteins A and B (omp A & omp B) was 6.2% (12/192) including 7.4% (8/108) in adults and 4.7% (4/84) in paediatric patients with AUFI. Phylogenetic analysis of SFGR based on the concatenated sequences of omp A-gltA-17kDa-omp B showed that the patients' isolates obtained in the study clustered with Rickettsia conorii str. Malish 7 (AE006914.1). The SFGR cases described here, to the best of our knowledge, are the first human cases diagnosed in Odisha, eastern coastal India that were laboratory-confirmed by molecular detection and sequencing. The findings of this study will be beneficial for designing systematic future studies covering more geographical locations for continued surveillance of SFGR human infections along with vector surveillance.