RESUMEN
Background Climate change leads to frequent heavy rainfall events, and higher incidences of bacillary dysentery after heavy rainfall have been observed. The impacts of heavy rainfall and its antecedent rainfall conditions on the disease are worth paying attention to. Objective To quantitatively analyze how the relationship between heavy rainfall events and bacillary dysentery occurrence is modified by antecedent rainfall conditions in Anhui Province and explore the different moderation effects in urban and rural contexts. Methods CN05.1 meteorological data of Anhui Province and cases of bacillary dysentery of the same area were collected from January 1, 2006 to August 31, 2017. An exposure-response Poisson regression model of heavy rainfall events and the number of daily cases was constructed to explore the moderation effect of antecedent rainfall conditions on the incidence of bacillary dysentery, and further stratified by urban and rural areas. Results This study included 129 459 cases of bacillary dysentery, with a daily average of 30.39. Compared with dry antecedent conditions without heavy rainfall, dry antecedent conditions with heavy rainfall had no obvious different effect on the incidence of bacillary dysentery for the whole province (P>0.05). But wet antecedent conditions significantly increased the risk of bacillary dysentery for the whole province after heavy rainfall (wet antecedent conditions without heavy rainfall: RR=1.281, 95%CI: 1.264-1.298; wet antecedent conditions with heavy rainfall: RR=1.267, 95%CI: 1.167-1.376). After urban and rural stratification, antecedent rainfall conditions also showed a significant moderation effect on the incidence of bacillary dysentery following heavy rainfall events. Compared with dry antecedent conditions without heavy rainfall, dry antecedent conditions with heavy rainfall had no obvious effect on the incidence of bacillary dysentery for the urban and the rural populations (P > 0.05). However, wet antecedent conditions without heavy rainfall (urban: RR=1.391, 95%CI: 1.362-1.421; rural: RR=1.222, 95%CI: 1.201-1.243) and wet antecedent conditions with heavy rainfall (urban: RR=1.364, 95%CI: 1.193-1.559; rural: RR=1.218, 95%CI: 1.098-1.352) significantly increased the risk of bacillary dysentery in both rural and urban areas. Conclusion In the influence of heavy rainfall on the incidence of bacillary dysentery in Anhui Province, antecedent rainfall conditions have a certain moderation effect in the whole province and in both urban and rural areas, and the risk of bacillary dysentery is increased under wet antecedent conditions.
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To understand the mechanism of phytoplankton bloom forming, we investigated the relationship between several species and water quality factors using long-term monitoring datasets from 1996 to 2003. The seven sites at this study were classified into four groups by phytoplankton species or water quality datasets and the species for phytoplankton bloom forming seems to be mainly influenced by the water quality or surrounding water conditions. E. gymnastica and P. minimum were observed for the longest time period from April to September, and C. polykrikoides shortest time period from summer to autumn. E. gymnastica was observed across the widest temperature range (14–27ºC), and C. polykrikoides narrowest temperature range (20–28ºC). Chaetoceros spp. was observed over the narrowest salinity range (22–33 ppt), and E. gymnastica, P. minimum, H. akashiwo wide salinity range (14–34 ppt). The main reasons for the formation of Chaetoceros spp. and S. costatum blooms seems to be fresh water input through forest and fields by heavy rainfall events. Thalassiosira spp. seems to grow well in conditions of fresh water input and/or in eutrophicated areas with salinities >20 ppt and water temperatures >17ºC. C. furca seems to grow well in sea areas that are affected by inflows of domestic and industrial wastewater and by inflows of freshwater with domestic and industrial wastewater, rather than only freshwater input, after May when water temperatures are higher than 18ºC. E. gymnastica, H. akashiwo, P. minimum, and P. triestinum seem to grow well in eutrophicated sea areas where nutrient levels are high and where domestic and industrial wastewater flow are abundant. C. polykrikoides blooms seem to be due to suitable seawater input from off sea areas, and freshwater after heavy rainfall that has high nitrogen concentration.