Epidemiology of hospitalized strongyloidiasis in Japan: A nationwide administrative database study

Strongyloidiasis remains endemic in parts of Japan, particularly Okinawa Prefecture, and can progress to disseminated disease with high mortality; however, nationwide data on hospitalized patients, including regional differences and the impact of disseminated disease, are limited. We conducted a retrospective nationwide study using the Diagnosis Procedure Combination database to identify hospitalized patients with strongyloidiasis in Japan between fiscal years 2014 and 2020, using ICD-10 code B78, with disseminated cases defined as B78.7. Demographic characteristics, geographic distribution, and outcomes were analyzed, with a focus on disseminated disease and regional differences between Okinawa and other areas. After excluding duplicate cases, 252 hospitalized patients were included (mean age, 77.6 years; male-to-female ratio, 1.47). Most patients were from the Kyushu and Okinawa regions, with Okinawa accounting for 82.1% of cases. Disseminated strongyloidiasis was identified in 44 patients (17.5%) and was associated with poorer neurological status at admission and higher in-hospital mortality; 11 patients with disseminated disease died during hospitalization (25.0%). Severe complications, including sepsis (54.5%) and meningitis (25.0%), were frequently observed in disseminated cases. Patients hospitalized outside Okinawa were younger than those hospitalized in Okinawa, whereas the proportions of disseminated disease and in-hospital mortality did not differ significantly between regions. In Japan, hospitalized patients diagnosed with strongyloidiasis were predominantly concentrated in Okinawa; however, severe cases also occurred in other regions. These findings highlight the importance of considering strongyloidiasis in patients with relevant epidemiological backgrounds, particularly in the setting of immunosuppression, regardless of their current geographic location.