Incidence of human granulocytic anaplasmosis in returning travelers with fever

BACKGROUND: Although tick-borne pathogens have been reported as an important cause of imported fever, the incidence of Anaplasma phagocytophilum, the causative agent of human granulocytic anaplasmosis (HGA), in travelers is unknown. METHODS: We conducted a prospective cohort study to investigate the aetiologies of fever in returning travelers (November 2017-July 2019). Polymerase chain reaction (PCR) for msp2 gene amplification and indirect immunofluorescence assay (IFA) for A. phagocitophilum were performed in all returning travelers with undifferentiated non-malarial fever. RESULTS: Among 141 travelers included, 8 patients were diagnosed with probable or confirmed HGA. The overall incidence rate of HGA of 19.9 cases/1000 person-week of travel. The main destination of travel was Asia, accounting for 62.5% patients with HGA. Co-infections were found in 37.5% of patients with HGA. CONCLUSIONS: Diagnosis of HGA and empirical treatment with doxycycline should be considered in travelers with fever.