부산대학교 도서관

Background: Scrub typhus (ST) and murine typhus (MT) are common but poorly understood causes of fever in Laos. We examined the spatial and temporal distribution of ST and MT, with the intent of informing interventions to prevent and control both diseases. Methodology and principle findings: This study included samples submitted from 2003 to 2017 to Mahosot Hospital, Vientiane, for ST and MT investigation. Serum samples were tested using IgM rapid diagnostic tests. Patient demographic data along with meteorological and environmental data from Laos were analysed. Approximately 17% of patients were positive for either ST (1,337/8,150 patients tested) or MT (1,283/7,552 patients tested). While both diseases occurred in inhabitants from Vientiane Capital, from the univariable analysis MT was positively and ST negatively associated with residence in Vientiane Capital. ST was highly seasonal, with cases two times more likely to occur during the wet season months of July-September compared to the dry season whilst MT peaked in the dry season. Multivariable regression analysis linked ST incidence to fluctuations in relative humidity whereas MT was linked to variation in temperature. Patients with ST infection were more likely to come from villages with higher levels of surface flooding and vegetation in the 16 days leading up to diagnosis. Conclusions: The data suggest that as cities expand, high risk areas for MT will also expand. With global heating and risks of attendant higher precipitation, these data suggest that the incidence and spatial distribution of both MT and ST will increase. Author summary: These data from Laos strongly support the hypothesis that murine typhus and scrub typhus are more urban and rural diseases, respectively. Risks of scrub typhus were associated with visiting rice fields and forests, with surface flooding and higher vegetation density. Risks of murine typhus were living in Vientiane City and not having visited rice fields and forests. Homes of patients with scrub typhus were consistently further away from the city centre and from roads than for those of patients with murine typhus. With the outward spread of higher house density with city expansion during the study, murine typhus spread outwards whilst scrub typhus receded. Temporal trends in incidence were associated, for murine typhus, with higher temperature and, for scrub typhus, with higher rainfall, humidity and flooding. In areas where both diseases are found, these data suggest that residence, occupational and climatic differential risks are useful for assisting with identifying patients. The data also suggest that as cities further enlarge, high risk areas for murine typhus will expand. With global heating and risks of attendant higher precipitation, these data also suggest that the incidence and spatial distribution of both murine typhus and scrub typhus will increase. [ABSTRACT FROM AUTHOR]