Abstract: Objective To conduct a molecular epidemiological tracing and analysis of Yersinia pestis strains isolated from two human plague outbreaks with unknown sources in Gansu Province, China. The results of this analysis would provide a basis for isolating and controlling the sources of Yersinia pestis. Methods The strains of Yersinia pestis isolated from two human plague outbreaks occurring on December 12, 2017, and September 27, 2019 were genotyped by the different region (DFR) and the clustered regularly interspaced short palindromic repeats (CRISPR). The repeat numbers of the variable number tandem repeat (VNTR) loci in the tested strains of Yersinia pestis were calculated by the multiple variable number tandem repeats analysis (MLVA), and the location of the phylogenetic tree of the tested strains was determined with the method of minimum spanning tree (MST) by the software BioNumerics 6.6. Results The strain of 20171212 lacked DFR01, DFR02, DFR03, DFR04, DFR13, DFR23, and the DFR type was identified as type 8. The space sequence of YPa was a1'-a2-a3-a4-a5-a6-a7-a35, the space sequence of YPb was b1-b2-b3-b4, the space sequence of YPc was c1-c2-c3, the gene cluster of CRISPR was Ca35', the genotype of CRISPR was 26'. MLVA clustering analysis showed that the strain clustered within in the cluster of Yuerhong pasture in Subei County and formed an independent branch. On the other hand, the strain of 20190927 lacked DFR01, DFR13 and DFR23, with the DFR type identified as type 1b. The space sequence of YPa was a1-a2-a3-a4-a5-a6-a7, the space sequence of YPb was b1-b2-b3-b4, the space sequence of YPc was c1-c2-c3, the gene cluster of CRSIPR was Ca7, the genotype of CRSIPR was 22 MLVA clustering analysis showed that the strain was located close to the cluster of Dangjinshan in Akesai County, and relatively distant from the cluster of Yuerhong pasture in Subei County. Conclusions The genotypes of strain 20171212 by DFR and CRISPR were consistent with the main genotypes of Y. pestis from Himalayana Marmota foci in Subei County, which confirmed that the human plague cases were naturally occurring locally. However, the strain gathered the cluster of Yuerhong pasture in Subei County, which indicated that the source of infection was not in Yanchiwan Town, but in the surrounding area of the Yuerhong pasture. The genotypes of strain 20190927 by DFR and CRISPR were in accordance with the main genotype of Y. pestis from Himalayana Marmota foci in Akesai County and were closer to the cluster of Dangjinshan in Aksai County than to

Plague natural foci in Gansu Province are large in area and widely distributed, and the epidemic status is different in each focus. Some plague natural foci have been resting for many years and are under stable control. In other plague natural foci, the epidemic of plague among animals is relatively active, and dozens of strains of Yersinia pestis can be isolated every year. The plague among animals spreads to the humans from time to time, and the cases of human plague are more severe, short in course of disease, and high in mortality. In recent years, with the sharp increase of migrant workers engaged in grazing and engineering construction in plague natural foci, opportunities to actively contact infected animals such as marmots, hares and sheepdogs have increased, resulting in an increase of human plague cases. In addition, the behaviors of illegal hunting, trafficking and sale of marmots cannot be stopped, resulting in human plague throughout the year. Therefore, the party committees and governments at all levels and the health administrative departments in Gansu Province have formulated the plague prevention and control measures suitable for this region according to the epidemic characteristics of plague among animals and humans. In this paper, the characteristics of plague epidemic situation at present and the prevention and control measures adopted in Gansu Province are discussed, in order to provide scientific basis and guidance for optimizing plague prevention and control measures in the future.

Objective: To analyze the spatial temporal distribution characteristics of tuberculosis among high school students at county levels in Gansu Province from 2018 to 2022,so as to provide a scientific basis for tuberculosis prevention and control in schools. Methods: Tuberculosis data from high school students in counties (districts) reported in Gansu Province from 2018 to 2022 was collected from the Tuberculosis Information Management System and Infectious Disease Information Reporting System of the Chinese Disease Prevention and Control Information Management System. Demographic data of high school students in counties (districts) came from the General Management System of the Chinese Disease Prevention and Control Information Management System, and the spatial clustering of the reported incidence rate of pulmonary tuberculosis among high school students in Gansu Province in the past five years was analyzed using the methods of global spatial autocorrelation (Moran s I) and local indicators of spatial audocorrelation(LISA). Results: A total of 41 885 pulmonary tuberculosis cases were reported in various counties of Gansu Province From 2018 to 2022, with an average reported incidence rate of 32.81/100 000. During the same period, 1 170 high school students cases were reported, with an average reported incidence rate of 13.72/100 000. With the exception of 2020, the reported incidence rate of pulmonary tuberculosis among high school students was non random distribution in other 4 years, showed a moderate intensity of spatial clustering. From 2018 to 2022, most counties in Gansu Province reported that the incidence rate of pulmonary tuberculosis among high school students was 10.00/100 000 or below, the counties with reported incidence rate >40.00/100 000 were mainly distributed in Luqu County, Maqu County, Diebu County, Hezuo City, Xiahe County of Gannan Prefecture, Gangu County and Wushan County of Tianshui Prefecture, Wenxian County and Kangxian County of Longnan Prefecture, Huachi County of Pingliang Prefecture, Huanxian County of Qingyang Prefecture. The number of counties where the reported incidence rate of tuberculosis among high school students more than 30.00/100 000 gradually decreased from 2018 to 2022. In the past five years, the reported incidence rate of tuberculosis among high school students in all counties of Gannan Prefecture remained above 40.00/ 100 000 . The LISA analysis results showed that the high incidence areas were mainly concentrated in Gannan Prefecture. Conclusions The epidemic situation of pulmonary tuberculosis among high school students in Gansu province from 2018 to 2022 is still a serious condition, showing the characteristics of unbalanced regional distribution. The reported incidence rate shows a strong spatial clustering, and the hot spots are concentrated in the counties (districts) of Gannan prefecture in Gansu Province.

Objective:To analyze the changes of spatial, seasonal, and age distribution of brucellosis among humans and animals in Gansu Province and to provide a reference for the next step in formulating prevention and control measures.Methods:Reported data of brucellosis of humans and animals in Gansu Province from 2018 to 2020 were collected. The human epidemic data were obtained from "China Disease Control and Prevention Information System", and the positive data of animals were obtained from the monthly report provided by Gansu Animal Disease Control Center. Human brucellosis was classified and analyzed according to year, month, age and region, and livestock brucellosis was classified according to year, month, population and region. ArcGIS 10.2 software was used to analyze the spatial epidemiological characteristics of the data. Measuring Geographic tool was used to calculate the shifting distance of the center of the disease incidence in humans and animals from 2018 to 2020.Results:From 2018 to 2020, a total of 6 375 cases of human brucellosis were reported in Gansu Province. The 40 - 59 age group accounted for 54.96% (3 504/6 375), 1 584 cases were reported in 2018, 1 787 cases were reported in 2019, and 3 004 cases were reported in 2020. The high incidence time of human brucellosis was July and November. A total of 48 180 brucellosis-positive animals (heads) were detected, of which 47 342 were positive sheep, accounting for 98.26% (47 342/48 180). The high incidence time of brucellosis among animals was October. Among the 14 cities (prefectures), the top cities of livestock brucellosis reported were Qingyang City, Zhangye City and Jiuquan City. The center of disease incidence among humans was located in Gulang County, Wuwei City. The center of disease incidence among animals was located in Wuwei City in 2018 and Qingyang City in 2020.Conclusions:The cases of brucellosis in humans and animals in Gansu Province are on the increase. In some areas, there are problems of separation of human and animal epidemics. It is necessary to actively strengthen monitoring and implement measures to prevent and control brucellosis in humans and animals in high-risk areas to curb the spread of the epidemic.

Objective:To analyze and predict the transmission risk of visceral leishmaniasis in Gansu Province based on an ecological niche model, providing a basis for the development of precise prevention and control measures and epidemic surveillance.Methods:The information of reported cases of visceral leishmaniasis in Gansu Province from 2015 to 2021 were collected from the National Infectious Disease Reporting Information Management System, and the longitude and latitude coordinates of the distribution points of cases and the data of 19 climate variables, 5 geographical variables and 2 socio-economic variables within the region were obtained. Based on an ecological niche model, a model for predicting the transmission risk of visceral leishmaniasis was constructed using the maximum entropy algorithm (MaxEnt), and its performance was evaluated by the area under the receiver operating characteristic curve (AUC). Then the importance of each environmental variable of the model was evaluated, and the distribution area of visceral leishmaniasis transmission risk in Gansu Province was predicted.Results:A total of 368 cases of visceral leishmaniasis were reported in Gansu Province from 2015 to 2021, of which 89.13% (328/368) were from Longnan City and Gannan Tibetan Autonomous Prefecture (Gannan Prefecture). The number of cases peaked in 2017 (79 cases, 21.47%). The model had high prediction accuracy (AUC = 0.985). The results of model analysis showed that the important climate variable affecting the distribution of visceral leishmaniasis was the average temperature in the coldest quarter (contribution value of 3.1), the geographical variables were land use type (contribution value of 52.6) and vegetation cover type (contribution value of 8.5), and the socio-economic variable was population size (contribution value of 14.3). The distribution results of transmission risk showed that high, medium and low risk areas exhibited a gradual transition from the southern part to the northwest part of Gansu Province. The high risk areas were mainly located in the central and southern parts of Longnan City and the southern part of Gannan Prefecture, accounting for 0.18% of the total area of the province. Medium and low risk areas accounted for 0.48% and 2.47% of the total area of the province, respectively; and areas with no risk accounted for 96.87%.Conclusions:The ecological niche model predicts that the spread of visceral leishmaniasis in Gansu Province is characterized by point like dispersion and local high aggregation distribution. It is necessary to strengthen monitoring and prevention and control of high-risk areas such as Longnan City and Gannan Prefecture.

Objective:To investigate the epidemiological situation of drinking water-type endemic fluorosis in Gansu Province, and scientifically evaluate the effectiveness of water improvement and fluoride reduction projects in preventing and controlling the disease.Methods:The drinking water-type endemic fluorosis areas in Gansu Province were divided into five regions according to different ecological types: the Longzhong Loess Plateau Hilly Area in central Gansu, the Longdong Loess Plateau Gully Area in eastern Gansu, the Longnan Qinling Zhongshan Canyon Area in southern Gansu, the Gobi area of the Hexi Desert, and the Alpine Grassland Meadow Area in southern Gansu. In 2021, a survey was conducted on the basic situation, running situation of the water improvement and fluoride reduction projects, fluoride content in drinking water(fluorine ion-selective electrode), and the prevalence of dental fluorosis (Dean) among children aged 8 to 12 in all drinking water-type endemic fluorosis villages in the five regions. The pertinent assessments were executed in accordance with national guidelines such as the "Standards for Drinking Water Quality" (GB 5749-2006) and "Diagnosis of Dental Fluorosis" (WS/T 208-2011).Results:A total of 2 000 villages in drinking water-type endemic fluorosis areas were monitored, among which 1 999 villages had implemented water improvement and fluoride reduction projects, with a coverage rate of 99.95% (1 999/2 000). All water improvement and fluoride reduction projects were operating normally, with no intermittent operation or scrapping. A total of 34 616 children aged 8 to 12 were investigated for dental fluorosis. The detection rate of dental fluorosis was 4.18% (1 448/34 616), and the dental fluorosis index was 0.09. There was a statistically significant difference in the detection rate of dental fluorosis among children of different ages (χ 2 = 69.77, P < 0.001). The difference in the detection rate of dental fluorosis among children of different ecological types of areas was statistically significant (χ 2 = 775.11, P < 0.001). The dental fluorosis index of children aged 8 - 12 was significantly correlated with the historical water fluoride level ( r = 0.29, P = 0.042). The water improvement time in the Gobi area of the Hexi Desert was significantly correlated with the detection rate of dental fluorosis in local children ( r = - 0.48, P = 0.023). Conclusions:In 2021, the prevention and control of drinking water-type endemic fluorosis in all villages in Gansu Province has reached the national control standards. However, due to the different ecological characteristics and changes in water source distribution in different ecological types of areas, it is still necessary to further strengthen the monitoring of the condition of drinking water-type endemic fluorosis in all the affected villages and consolidate the existing prevention and control achievements.

Objective:To investigate the intelligence status of children aged 10 - 12 in rural areas of Linxia Hui Autonomous Prefecture (referred to as Linxia) in Gansu Province.Methods:From September to November 2019, a cross-sectional study was carried out to investigate the intelligence status of children aged 10 to 12 in 8 counties (cities) of Linxia. Chinese Raven's Progressive Matrices (rural version) was used for intelligence test and children's intelligence quotient (IQ) was calculated by regular mold to evaluate children's intelligence level.Results:A total of 1 721 children in Linxia were tested for intelligence, with an average IQ of 103.2. Among them, low intelligence (≤69) accounted for 1.0% (18/1 721), borderline (70 - 79) accounted for 3.0% (52/1 721), middle and lower (80 - 89) accounted for 8.4% (144/1 721), moderate (90 - 109) accounted for 56.6% (974/1 721), middle and upper (110 - 119) accounted for 21.9% (377/1 721), excellent (120 - 129) accounted for 7.8% (135/1 721), extremely excellent (≥130) accounted for 1.2% (21/1 721). There were 635, 598 and 488 children aged 10, 11 and 12, respectively, with an average IQ of 106.1, 103.3 and 99.2. There were 919 males and 802 females, with an average IQ of 102.9 and 103.4, respectively.Conclusion:In 2019, the intelligence of children aged 10 to 12 in rural areas of Linxia has reached the moderate level.

Objective:To study the genotyping and regional distribution characteristics of Yersinia pestis by single nucleotide polymorphism (SNP) in Gansu Province. Methods:A total of 52 strains of Yersinia pestis isolated from Himalaya Marmot plague foci and Spermophilus alaschanicus plague foci in Gansu Province from 1962 to 2017 were selected for culture and extraction of DNA. The genomic DNA of Yersinia pestis was sequenced by the second generation of Illumina PE150 to identify the SNP sites. The species characteristics of Yersinia pestis in Gansu Province was determined by the Kimura-2-parameter model of neighbor joining of Mega 10.0 software based on the SNP sites. The molecular evolutionary tree of the groups was determined by Hasegawa-Kishino-Yano model of maximum likelihood method according to the SNP sites. Results:A total of 103 SNP sites were identified in 52 strains of Yersinia pestis in Gansu Province, including 28 intergenic loci, 43 non-synonymous mutations, 31 synonymous mutations and 1 nonsense mutation. The 52 strains of Yersinia pestis were divided into 2 biotypes and 3 groups, which were ancient type (1.IN2, 3.ANT) and medieval type (2.MED). Among them, 35 strains belonged to 1.IN2 group, 13 strains belonged to 3.ANT group, and 4 strains belonged to 2.MED group. The 1.IN2 group was further divided into 5 subgroups: the groups of Yuerhong Town and Dangchengwan Town in Subei County, the groups of Mati Town and Dahe Town in Sunan County, and the group of Xiahe County. The 3.ANT group was further divided into 2 subgroups: the groups of Hongliuwan Town in Aksay County and Machang in Dangchengwan Town of Subei County. Conclusion:The SNP method can be used to genotype Yersinia pestis from different plague foci in Gansu Province, which has certain regional characteristics.

Objective:To learn about the epidemic dynamics and spatial epidemic characteristics of human brucellosis in Gansu Province.Methods:Data on human brucellosis in Gansu Province reported by China Disease Control and Prevention Information System from January 2016 to December 2020 were collected and analyzed by descriptive epidemiology and spatial clustering analysis.Results:A total of 10 025 cases of human brucellosis were reported in Gansu Province from 2016 to 2020, with a statistically significant difference in incidence rate between years (χ 2 = 242.86, P = 0.001). The incidence was the lowest in 2018 (6.03/100 000), and the highest in 2020 (11.39/100 000). The reported cases were concentrated in 45 - 55 years old, accounting for 34.52% (3 461/10 025); the male to female ratio was 2.91 ∶ 1.00 (7 458/2 567); farmers were the main occupation, accounting for 82.11% (8 232/10 025). Among the 86 counties (cities, districts) in Gansu Province, Yongchang County had the highest number of reported cases in 2020 (339 cases), and Sunan Yugur Autonomous County had the highest incidence in 2020 (190.89/100 000). Spatial autocorrelation analysis showed that there was significant spatial positive correlation between the incidence rate of human brucellosis in Gansu Province from 2016 to 2020 (global Moran's I > 0, Z > 1.96, P < 0.05), showing a spatial clustering distribution. The high-high clustering areas were concentrated in Yongchang County and Sunan Yugur Autonomous County. Conclusion:In Gansu Province, the main population of human brucellosis is middle-aged male farmers, and the incidence of brucellosis is spatially clustered.

Objective:To analyze the epidemic status and spatial and temporal cluster distribution of visceral leishmaniasis (VL) in Gansu Province, and to provide evidence for making precise prevention and control measures and epidemic surveillance.Methods:The data of VL cases in Gansu Province reported in the China Disease Prevention and Control Information System Infectious Disease Reporting Information Management System from 2015 to 2021 were collected, descriptive epidemiology analysis was performed (three distribution of the disease). SaTScan v9.6 and ArcMap 10.7 were used for spatio-temporal cluster analysis.Results:A total of 368 VL cases were reported from 2015 to 2021, 89.13% (328/368) were concentrated in Longnan City and Gannan Tibetan Autonomous Prefecture. The number of VL cases increased year by year from 2015 to 2017, reaching a peak in 2017 (79 cases, accounting for 21.47%), and had decreased year by year since 2018. There were cases every month throughout the year, and the peak was in April in spring (38 cases). The ratio of male to female patients was 1.3 ∶ 1.0 (208/160). Scattered children aged less than 5 years old were more common (41.30%, 152/368). The spatio-temporal cluster analysis showed that both the spatial and temporal aggregation zones of VL in Tanchang County and Chengxian County were of statistical significance ( P < 0.05). Conclusion:The incidence of VL in Gansu Province is showing a low epidemic trend, having spatio-temporal aggregation, and precise monitoring and prevention and control should be strengthened in epidemic areas with different prevalence levels.