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 study the epidemic situation of Marmota himalayana plague and Yersinias infection in Yugur Autonomous County of Sunan (Sunan County) of Gansu Province, and to provide new ideas for prevention and control of plague. Methods:From 2014 to 2018, liver and spleen, cecum, throat swabs and blood samples of Marmota himalayana were collected on the spot in Sunan County, where Yersinia strains were isolated and identified, and plague F1 antigen and antibody were detected. Results:A total of 634 liver and spleen samples, 427 cecum samples and 426 throat swabs samples were collected from Marmota himalayana, and 23 strains of Yersinia pestis, 2 strains of Yersinia marcescens, and 1 strain of Yersinia flexneri were detected, with the detection rates of 3.63% (23/634), 0.47% (2/427) and 0.23% (1/426), respectively. The detection rate of Yersinia pestis in different years was statistically significantly different (χ 2 = 13.19, P = 0.010). A total of 1 822 serum samples of Marmota himalayana were detected, and 5 F1 antibody positive samples were detected, with a positive rate of 0.27%, the difference of positive rate between different years was statistically significant (χ 2 = 25.22, P < 0.001); 282 liver and spleen tissue homogenates of Marmota himalayana were detected, 22 F1 antigen positive samples were detected, the positive rate was 7.80%, and there was no statistically significant difference between different years (χ 2 = 7.85, P = 0.097). The 23 strains of Yersinia pestis detected were distributed in Mati Tibetan Township (12 strains), Dahe Township (6 strains) and Qifeng Tibetan Township (5 strains); 1 strain of Yersinia flexneri and 2 strains of Yersinia marcescens were both located in Dahe Township. Conclusion:There is an epidemic of plague among animals in Sunan County from 2014 to 2018, and the areas where Yersinia pestis and non pathogenic Yersinia are detected overlapped.

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

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.

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 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 understand the plague epidemic characteristics in the natural foci of the Qilian Mountains-A-erh-chin Mountains Himalayan marmot plague in Gansu Province, and to provide scientific basis for innovative prevention and control of the plague in combination with local conditions. Methods:A retrospective study was used to collect the monitoring data of the natural foci of plague in Gansu Province from 2011 to 2018 (from the epidemic surveillance files of the Center for Disease Control and Prevention of Gansu Province and direct network reporting information). Descriptive epidemiological method was used to analyze the plague epidemic characteristics of natural foci of the Qilian Mountains-A-erh-chin Mountains Himalayan marmot plague in Gansu Province from 2011 to 2018, including the distribution of host animals, pathogenic and serological testing of the plague bacteria, and the epidemic characteristics of human plague. Results:From 2011 to 2018, the total average marmot density in the natural foci of the Qilian Mountains-A-erh-chin Mountains Himalayan marmot plague in Gansu Province was 0.21/hm 2, of which Tianzhu County had the highest average marmot density of 0.58/hm 2, and Jiayuguan City had the lowest average marmot density of 0.01/hm 2. A total of 381 strains of Yersinia pestis were isolated in the foci, of which 4 were isolated from human corpses, 298 were host animals, and 79 were infectious vectors. Among them, the top 3 counties (cities) of isolated strains were Aksai County (38.85%, 148 strains), Subei County (31.50%, 120 strains) and Yumen City (16.27%, 62 strains). A total of 6 860 marmot serum, 1 769 dog serum were tested, the F1 antibody positive rates were 2.70% (185/6 860), 8.42% (149/1 769); and the F1 antigen positive rate of 814 animal materials was 4.30% (35/814), respectively. There were 4 times of human plague, 4 cases occurred and 4 cases died; 3 times occurred in Subei County and 1 time in Yumen City. The onset months were July, September, November and December. Active contact with infected animals such as shepherd dogs was the main route of infection, and migrant herders were the key occupation population. Conclusions:The animal epidemic situation in the natural foci of the Qilian Mountains-A-erh-chin Mountains Himalayan marmot plague in Gansu Province is active, and the plague presents different epidemic states in different regions. The prevention and control measures should be taken according to local conditions and guided by classification to strictly prevent the occurrence and transmission of the plague.

Objective:To investigate the infection status of Yersinia in the main host animals of plague in Xiahe and Luqu counties, the Himalayan marmot plague foci of Gansu Province, and to provide a basis for exploring the epidemic status of plague in these foci. Methods:Samples of the ileocecal region and contents, pharyngeal swabs (or tongue roots), and blood of the main host animals of plague in Xiahe County and Luqu County where the plague were active in the 1950s and 1960s were collected from 2014 to 2018. The Yersinia isolation, virulence determination and F1 antibody detection were performed, respectively. Results:Totally 24 strains of Yersinia were detected in 958 samples of ileocecal region and contents with a bacterial detection rate of 2.51%, which were 13 strains of Yersinia enterocolitia (Y.e), 1 strain of Yersinia kristensenii (Y.k), 2 strains of Yersinia frederiksenii/ intermedia (Y.f/i), 6 strains of Yersinia intermedia (Y.i), 1 strain of Yersinia aldouae (Y.a) and 1 strain of Yersinia massiliensis (Y.m). Totally 19 strains of Yersinia were detected in 958 samples of pharyngeal swabs (or tongue roots), and the detection rate was 1.98%, which were 8 strains of Y.e, 1 strain of Yersinia pseudotuberculosis (Y.p), 4 strains of Y.k, 1 strain of Y.f/i, 4 strains of Y.i, and 1 strain of Yersinia ruckeri (Y.r). The virulence types of 21 strains of Y.e were ail -ystA -ystB +yadA -virF -rfbc -, ail -ystA -ystB -yadA -virF -rfbc -, respectively, accounting for 9.52% (2/21) and 90.48% (19/21), none were pathogenic. The results of F1 antibody in 1 079 serum samples were all negative. Conclusions:Yersinia are widely found in the pharynx and intestines of the main host animals of plague in Xiahe and Luqu counties, and the Y.e detected are all non-pathogenic strains. The results of this investigation can provide clues for further study on the preservation of Yersinia pestis in host animals and their living environment.

Objective:To assess the impact of vaccination at school and influenza vaccination rates among school-age children on school absenteeism in Shenzhen.Methods:The study subjects were primary school students in Shenzhen. School absenteeism panel database from December 2017 to June 2020 of 286 primary schools in Shenzhen was merged with vaccination rates and organizational patterns ( i.e., vaccination at school vs. non-school) data of 9 districts in Shenzhen after influenza vaccination for children. The outcome was the number of school absenteeism. The treatment and control groups were distinguished by organizational patterns and district vaccination rates. Difference-in-Difference (DiD) Poisson regressions were used to analyze the effectiveness of vaccination at school and higher vaccination rates. Besides, a robustness test was performed on the regression results. Results:Poisson regression analysis and robustness test of regression results showed that vaccination at school and higher vaccination rates effectively reduced the risk of school absenteeism, with effectiveness against absenteeism of 32.6% (95% CI: 17.0%-45.3%, P<0.01) and 53.0% (95% CI: 42.1%-61.8%, P<0.01), respectively. Conclusion:A free influenza vaccination program for school-age children in Shenzhen and prioritizing school-based vaccination may be an effective measure to reduce the risk of school absenteeism.

Objective:To analyse the effects of meteorological factors on plague epidemic in Himalayana marmot plague natural foci in Subei and Sunan counties of Gansu Province. Methods:The surveillance data of plague from 1973 to 2016 in Himalayan marmot foci of Subei and Sunan counties (from Gansu Provincial Center for Disease Control and Prevention) and the meteorological factors (rainfall, temperature, relative humidity) of current, preceding first, second and third years (the first, second and third years before the reference year, from China Meteorological Data Sharing Service System) were collected. In order to build generalized additive model (GAM), the positive rate of plague was used as dependent variable while meteorological factors of the current, preceding first, second and third years were used as independent variables. The influence of meteorological factors on plague was quantitatively analyzed by using R2.3.2 software. Results:In 2006 - 2016, compared with 1974 - 1983, the average temperature in Subei rose by 0.99 ℃, the average relative humidity rose by 3.55%RH, and the average rainfall rose by 12.16 mm; in Sunan County, the average temperature rose by 1.00 ℃, the average relative humidity rose by 2.01%RH, and the average rainfall rose by 14.60 mm. From 1973 to 2016, 11 cases of human plague with 7 cases of dead (12 cases of attack) occurred in the investigated district. The average rainfall of the preceding third year of Subei rose every 1.00 mm within a certain range, the animal plague occurred rose by 0.40%. The average relative humidity of preceding second year of Subei rose every 1.00%RH within a certain range, animal plague occurred rose by 11.66%. The average rainfall of the preceding first year of Sunan rose every 1.00 mm within a certain range, the animal plague occurred rose by 1.32%. The average relative humidity of preceding third year of Sunan rose every 1.00%RH within a certain range, animal plague occurred rose by 11.96%. The average temperature of the preceding second year of Subei, Sunan rose every 1.00 ℃ within a certain range, animal plague rose 73.17%, 70.18%, respectively.Conclusions:The occurrence and prevalence of plague in Himalayana marmot are closely related to meteorological factors, and the temperature within a certain range (but not continuously) not only promotes the epidemic of plague, but also has a lag effect. In addition, the effects of different types of climate in the same foci on the prevalence of animal plague vary.