<i>Coxiella burnetii</i> and <i>Bartonella</i> species serology of febrile patients with an established infectious or inflammatory diagnosis in Sudan, Nepal, and Cambodia

<i>Coxiella burnetii</i> and <i>Bartonella</i> spp. are important but under-recognized causes of febrile illness and infective endocarditis in low- and middle-income countries (LMICs). This study evaluated the seroprevalence of these pathogens among patients with confirmed causes of persistent fever in Sudan, Nepal, and Cambodia. Despite the diagnostic utility of serologic testing for these infections, its performance in LMICs-where co-infections and background seropositivity are common-remains poorly characterized. The findings suggest notable seropositivity for <i>C. burnetii</i> and <i>Bartonella</i> among patients with a set of tropical and inflammatory diagnoses, including visceral leishmaniasis, <i>Plasmodium falciparum</i> malaria, leptospirosis, brucellosis, scrub typhus, and systemic lupus erythematosus. These results highlight the potential for cross-reactivity and underscore the need for context-specific validation. Enhanced understanding of serologic test characteristics is essential for accurate diagnosis in resource-limited settings.