title: Correlation between infectious disease and soil radiation in Japan: an exploratory study using national sentinel surveillance data.
abstract: We investigated the relationship between epidemics and soil radiation through an exploratory study using sentinel surveillance data (individuals aged <20 years) during the last three epidemic seasons of influenza and norovirus in Japan. We used a spatial analysis method of a geographical information system (GIS). We mapped the epidemic spreading patterns from sentinel incidence rates. We calculated the average soil radiation [dm (μGy/h)] for each sentinel site using data on uranium, thorium, and potassium oxide in the soil and examined the incidence rate in units of 0·01 μGy/h. The correlations between the incidence rate and the average soil radiation were assessed. Epidemic clusters of influenza and norovirus infections were observed in areas with relatively high radiation exposure. A positive correlation was detected between the average incidence rate and radiation dose, at r = 0·61-0·84 (P < 0·01) for influenza infections and r = 0·61-0·72 (P < 0·01) for norovirus infections. An increase in the incidence rate was found between areas with radiation exposure of 0 < dm < 0·01 and 0·15 ⩽ dm < 0·16, at 1·80 [95% confidence interval (CI) 1·47-2·12] times higher for influenza infection and 2·07 (95% CI 1·53-2·61) times higher for norovirus infection. Our results suggest a potential association between decreased immunity and irradiation because of soil radiation. Further studies on immunity in these epidemic-prone areas are desirable.
authors.affiliation: Department of Epidemiology,Graduate School of Medicine,Dentistry and Pharmaceutical Sciences,Okayama University,Okayama,Japan.
authors.forename: S
authors.initials: S
authors.lastname: Inaida
authors.affiliation: Department of Human Ecology,Graduate School of Environmental and Life Sciences,Okayama University,Okayama,Japan.
authors.forename: T
authors.initials: T
authors.lastname: Tsuda
authors.affiliation: Biomedical Science Association,Tokyo,Japan.
authors.forename: S
authors.initials: S
authors.lastname: Matsuno
mesh_terms: D000293:Adolescent; D017250:Caliciviridae Infections / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007251:Influenza, Human / Q000453:epidemiology*; D007564:Japan / Q000453:epidemiology; D008297:Male; D029322:Norovirus / Q000302:isolation & purification; D009975:Orthomyxoviridae / Q000302:isolation & purification; D010087:Oxides / Q000032:analysis; D017680:Potassium Compounds / Q000032:analysis; D011827:Radiation; D018571:Sentinel Surveillance; D012987:Soil / Q000737:chemistry*; D013910:Thorium / Q000032:analysis; D019371:Topography, Medical; D014501:Uranium / Q000032:analysis; D055815:Young Adult
chemical_list: D010087:Oxides; D017680:Potassium Compounds; D012987:Soil; D014501:Uranium; C068440:potassium oxide; D013910:Thorium
keywords: Epidemic; geographical information system (GIS); influenza; national sentinel surveillance; norovirus; soil radiation