A new electrochemical sensor for organophosphate pesticide(methyl-paraoxon)detection based on bifunctional cerium oxide(CeO2)nanozyme is here reported for the first time.Methyl-paraoxon was degraded into p-nitrophenol by using CeO2 with phosphatase mimicking activity.The CeO2 nanozyme-modified electrode was then synthesized to detect p-nitrophenol.Cyclic voltammetry was applied to investigate the electrochemical behavior of the modified electrode,which indicates that the signal enhancement effect may attribute to the coating of CeO2 nanozyme.The current research also studied and discussed the main parameters affecting the analytical signal,including accumulation potential,accumulation time,and pH.Under the optimum conditions,the present method provided a wider linear range from 0.1 to 100 μmol/L for methyl-paraoxon with a detection limit of 0.06 μmol/L.To validate the proof of concept,the electrochemical sensor was then successfully applied for the determination of methyl-paraoxon in three herb samples,i.e.,Coix lacryma-jobi,Adenophora stricta and Semen nelum-binis.Our findings may provide new insights into the application of bifunctional nanozyme in electro-chemical detection of organophosphorus pesticide.

Objective:To develop a Risk Assessment Index System (RAIS) on HIV infection among young students based on Delphi method and to provide individual HIV infection risk assessment, targeted prevention and control measures.Methods:Delphi method was applied to determine the index system and weight of the assessment tool through three rounds of expert consultation and overall consideration of opinions and suggestions from 19 experts.Results:The positivity coefficients of three rounds of expert consultation were 100%. The authority coefficient of experts was between 0.887 and 0.945. The Kendall's W coefficients through first, second and third round specialist consultation was 0.379, 0.329 and 0.248, respectively (all P<0.001). The coefficients of variation in the third round were all less than 0.25, indicating that experts' opinion tend to be consistent and the results are highly reliable. The HIV infection risk assessment index system among young students consisted of 7 first grade indices and 54 second grade indices, of which weight was calculated. Conclusions:The RAIS on HIV infection for young students was initially established based on Delphi method, and could be used in the development of HIV infection risk assessment tools for personalized prevention and intervention among young students. However, the reliability, validity and effect of this assessment index system need to be further evaluated.

Objective:To explore the difference of sexual health characteristics and demands in students in different groups, and provide the basis for targeted sexual health eduction for AIDS prevention in young students.Methods:A survey was conducted based on the requirement of health education about sexual health and AIDS prevention in young students by the education department of Guangdong province. A two-step cluster analysis was performed on the survey data obtained by convenient sampling, the variables and number of clusters included were determined by combination of analysis results and professional knowledge. The demographic characteristics, the content and form of sexual health education needed were compared among different groups.Results:Survey data of 3 884 students were collected, and six variables were used for classification: cognition or occurrence masturbation, sexual behavior, frequency of sexual information acquisition, number of acceptable sex partners and AIDS knowledge awareness rate. By these variables, the students were classified into three levels of risk groups: high risk group (46.6%), medium risk group (39.9%) and low risk group (13.5%). As for demographic characteristics, high risk group, with a median age of 19 years, had the highest proportions of boys (65.9%), students with non-heterosexuality orientation (15.2%), urban residents (58.2%), only children (30.8%) and undergraduates (54.7%). Medium risk group, with a median age of 19 years, had the highest proportions of girls (82.7%) and vocational college students (34.0%). Low risk group, with a median age of 18 years, had the highest proportions of rural residents (52.4%), non-only child (80.6%), senior high school students (41.3%), non-boarding students (17.5%) and students without internship and part-time job experience (43.2%). In terms of health education demands, high risk group had a higher demand of information about self-identity, sexual safety, sexual decision making, contraception, abortion, and sexually transmitted disease or AIDS prevention. Medium risk group paid more attention to value on love and marriage, sexual assault. Low risk group showed a higher demand of adolescent physiology knowledge. Compared with low risk group, high risk group had a higher demand of peer education, Internet/multimedia, anonymous counseling and other forms of sexual health education. The differences were significant.Conclusion:The characteristics, sexual knowledge awareness, attitude and behavior, and health education demands of young students in different groups are different, so health education materials and methods should be developed according to the characteristics of different groups to enhance the acceptance and enthusiasm of students and improve the quality of sexual health education.

Objective:To analyze the influencing factors for HIV testing services utilization in students with self-assessed high risk of HIV infection.Methods:The research framework of the influencing factors for HIV testing services utilization in students was developed based on Andersen's health services utilization behavioral model and related literature. A cross-sectional survey was performed in students with self-assessed high risk of HIV infection by an online HIV infection risk assessment tool from March to April 2019. Multiple logistic regressions were applied with hierarchical model.Results:A total of 526 students were included in the study (age: 19.30±1.19 years old), in whom 96.2% agreed that HIV testing should be received after high-risk behavior. 56.7% (298/526) had sexual behavior and the HIV testing rate was 11.0% (58/526). The HIV testing rates in students who had and had no sex behavior were 13.42%(40/298) and 7.89% (18/228), respectively. According to the results from multivariate logistic regression analysis, non-heterosexual (compared with heterosexual, OR=7.88, 95% CI: 3.98-15.61) and higher score of AIDS knowledge awareness (compared with lower score, OR=2.05, 95% CI: 1.07-3.93) in propensity factor module, and having risk sexual behavior (compared with having no risk sexual behavior, OR=2.66, 95% CI: 1.41-5.03) and having diagnosis of STD infection in hospital (compared with having no such diagnosis, OR=6.35, 95% CI: 2.21-18.27) in demand factor module, and receiving health education about AIDS prevention in the past year (compared with receiving no such health education, OR=0.29, 95% CI: 0.11-0.76) and receiving health education about AIDS testing service in the past year (compared with receiving no such health education, OR=3.67, 95% CI: 1.71-7.90) in ability factor module were the influencing factors for utilization of HIV testing services. Conclusions:The acceptance of HIV testing in students needs to be improved urgently. Propensity factors, such as their AIDS knowledge awareness and sexual orientation, and demand factors, such as having risk sexual behavior and STD infection, have obvious impacts on the utilization of HIV testing services. However, health education about AIDS prevention and HIV testing service can play a more important role in facilitating the utilization of HIV testing in students. In the future, we should further strengthen the publicity of voluntary HIV counseling and testing service in students with particular attention to girls and those with risk sexual behaviors.

Objective:To evaluate the effect of "self-categorization" on decision of health preference and the influence of self-categorized deviation in knowledge, attitude and practice (KAP) on the willingness of seeking help for sexual health among young students.Methods:From March to April 2019, young students who used a WeChat applet for sexual health and HIV infection risk assessment, which is called "Detective Bear" were recruited and investigated. According to the consistency between the self-categorization of KAP for sexual health and the systematic categorization from their honest answers, the participants were allocated into three groups: consistent, low or high status, according to their judgment on sexual information acquisition, sexual attitude, and the actual number of sexual experiences. Logistic regression was used to analyze the differences in the willingness to seek help for sexual health problems between the three groups.Results:2 009 students with an average age of (19.2±1.1) were included. 54.7% (1 099/2 009) were female, and 98.4% (1 976/2 009) were college, undergraduate or postgraduate students. 49.0% (984/2 009) were in the consistent group, 10.9% (219/2 009) had a lower self-categorization, 40.1% (806/2 009) had a higher self-categorization. Compared with the consistent group, students with lower self-categorization of KAP for sexual health were less likely to assess HIV voluntary counseling and testing (a OR=0.65, 95% CI: 0.43-0.99). However, students with higher self-categorization seemed to dislike seeking help for sexually transmitted diseases (a OR=0.76, 95% CI: 0.59-0.98). Conclusions:Deviation in self-categorization of KAP for sexual health will reduce the young students' willingness to seek help for related problems. Especially those with lower self-categorization, lack of risk consciousness, and refuse to assess counseling and testing may increase the HIV/AIDS epidemic among this population. It is necessary to strengthen the capacity of self-assessment for young students while promoting sex education.

Objective:To summarize the design and analysis of testing results of a WeChat applet, which is called "Detective Bear", for sexual health and HIV infection risk assessment in young students, and evaluate its feasibility and effectiveness.Methods:Based on self-categorization theory, by using cluster analysis and Delphi expert consulting method, the framework of WeChat applet, risk assessment index system and preventive intervention content were determined. Young students were recruited by student associations for the application test, the results of the repeated tests and the satisfaction survey were collected and analyzed.Results:The study included 393 participants who repeated the test twice and 750 participants who volunteered to participate in the satisfaction questionnaire survey. The applet contains five modules: self-role judgment, self-test, risk assessment, assessment report generation and background management. The risk assessment module contains 6 first-level indicators and 55 second-level indicators. Assessment report generation module includes role diagnosis type, radar chart of HIV sexual health KAP and intervention prescription. In 393 students who repeated the test, the awareness of AIDS to be a serious sexually transmitted disease, the epidemic trend in young students in China, with active seeking HIV testing services and caring the infected improved. The satisfaction survey showed that 75.7% of students (568/750) accepted the applet, 86.5% (649/750) agreed the evaluation report, 83.1%(623/750) thought that there were some problems, but it was easy to use, 93.3% (700/750) said they can learn something from the applet and 84.1% (631/750) satisfied with the page design. Some students thought the questionnaire was too long and somewhat difficult to complete ( P<0.05), and some reported that more can be learned ( P<0.05). Conclusions:The applet integrates AIDS prevention related knowledge and practice into a challenging, interesting, interactive game and provide individualized, concrete risk assessment and self-intervention for young students, which can effectively help students to improve the awareness of AIDS related knowledge and get links for access to condoms, testing and other intervention services. However, its large-scale application and long-term effect need to be further tested.

Objective:To analyze the contagiousness and secondary attack rate of 2019 novel coronavirus in cluster epidemics in Guangzhou and provide evidence for the prevention and control of COVID-19.Methods:All the individuals identified to be infected with 2019-nCoV in Guangzhou, including confirmed cases and asymptomatic cases, were included and classified as imported cases and local cases. The first case of each cluster epidemic was defined as index case, and the number of subsequent infections was calculated to evaluate the contagiousness and secondary attack rate of 2019 novel coronavirus in the shortest incubation period of 1-3 days.Results:As of 18 February, 2020, a total of 349 cases of 2019-nCoV infection, including 339 confirmed cases (97.13 %) and 10 asymptomatic cases (2.87 %) were reported in Guangzhou. There were 68 clusters involving 217 2019-nCoV infection cases (210 confirmed cases and 7 asymptomatic cases). The median number of subsequent infections caused by an index case in a cluster epidemic was 3, among which 2 were confirmed cases and 1 was asymptomatic cases, respectively. The average number of contagiousness was 2.18 in shorted incubation period of 1-3 days (The average number of infected cases were 2.18 cases by the index case in a cluster epidemic), the average infection number in family members was 1.86, and the infection ratio of family member transmission was 85.32 % (1.86/2.18). The secondary attack rate in close contacts with shortest incubation period of 1-3 days was 17.12 %-18.99 %, the secondary attack rate in family members was 46.11 %-49.56 %. Conclusions:The cluster epidemic of COVID-19 in Guangzhou mainly occurred in families, the contagiousness was high. It is necessary to strengthen the prevention and control to reduce the community transmission of COVID-19.

Objective: To analyze the characteristics of the "Interner Plus-based AIDS Comprehensive Prevention Service System" among MSM who frequently using the Internet in Guangzhou. Methods: An online survey was conducted among MSM who were recruited through gay-website portals between August and September, 2018 in Guangzhou, to collect information regarding the use of and attitudes on the "Interner Plus-based AIDS Comprehensive Prevention Service System" . Logistic regression was used to explore the association between the use of Internet intervention tools and related behavioral characteristics. Information on the awareness of AIDS, HIV testing, and condomless anal sex behavior were compared between the core or non-core services users. Results: A total of 777 Internet-based MSM were recruited as participants including 638 men (82.1%) as core service users. MSM were satisfied in using the the "Interner Plus-based AIDS Comprehensive Prevention Service System" while more than 80.0% of the users felt that the tools were helpful in: increasing the HIV awareness, promoting test uptake, and reducing those related risk behavior. Comparing with those who did not use the tools, the users showed higher rates in practising condomless anal intercourse (1.50-1.86 times), commercial sex with men (11.60-21.21 times), and unprotected vaginal intercourse (13.62-20.67 times), in the last 6 months. Proportions of core service users appeared as: [96.6% vs. 74.8%, aOR (95%CI): 8.80 (4.85-15.97)] on HIV testing, [56.4% vs. 22.3%, aOR (95%CI): 4.54 (2.94-7.02)] on regular HIV testing and [86.2% vs. 80.6%, aOR (95%CI): 1.75 (1.06-2.89)] on awareness of HIV knowledge respectively, which were all significantly higher than the non-core service users. Conclusions The frequent Internet using MSM in Guangzhou claimed to have had high acceptance and satisfaction on the local Internet HIV intervention service tools. The "Internet Plus-based AIDS Comprehensive Prevention Service System" had effectively reached the high-risk subgroups of MSM, increasing the awareness on related risk and promoting testing on HIV.

Objective: This article was to evaluate the applicability and feasibility of "Lingnanzhun" -an "Internet Plus-based HIV Self-testing Tool" targeting MSM in Guangzhou. Hopefully, the results could be used to improve the existing HIV testing services and to support the implementation and scale-up of HIV self-testing programs. Methods: Data were collected from a survey on HIV testing preferences among the Internet-using MSM in April to June, 2015. Univariate and multivariate logistic regression analysis were applied to identify factors associated with the use of HIV self-testing service provided by Lingnanzhun. Information related to the users of Lingnanzhun during September 2014 and December 2018 was also collected. Results: 769 MSM were recruited as participants. Of them, age distribution was 16-77(28.6±6.8) years old, 88.3%(679/769) were unmarried, 42.2%(325/769) were registered residents of Guangzhou, 82.1%(631/769) had university or college education. Among them, 195 (25.4%) used the HIV self- testing program of Lingnanzhun while 574 (74.6%) using the clinic service. Compared with the clinic service users, the Lingnanzhun users showed the following characteristics: longer experience in the MSM community ≥10 years (32.8% vs. 20.9%, 64/195 vs. 120/574); having male casual sexual partners ≥2 (42.1% vs. 29.6%, 82/195 vs. 170/574); having group sex (6.2% vs. 2.6%, 12/195 vs. 15/574) and having commercial sex with men (13.8% vs. 3.0%, 27/195 vs. 17/574). Data from the Lingnanzhun users showed that a total of 3 000 users had practised 5 038 times of self HIV-testings. 11.4% (343/3 000) of the Lingnanzhun users had never been tested. Conclusions It was applicable and feasible to provide Internet-based HIV self-testing service to MSM as a significant complement to the traditional facility-based HIV testing services. It was also useful in accessing those who were having higher risk or had never received HIV testing so as to increase the testing uptake and the frequency.

Objective: To analyze the characteristics of levels related to the risk through self-evaluation system, among MSM users in Guangzhou, between 2015 and 2017. Methods: Between 2015 and 2017, data was collected from the users of a self-evaluation system network related to HIV infection, based on the previous 'HIV health risk appraisal model’. Information on risk factors was collected to calculate the scores and levels of risks and to estimate the incidence of HIV. Taking the reference of R value on risks as (R=0.9-1.1) in general population. The ones with very low risk, with low risk, moderate risk, high risk and very high risk were set as R≤0.5, 0.5<R≤0.9, 0.9<R≤1.1, 1.1< R≤2.0 and R>2.0, respectively. The scores of modifiable risk factors were compared with different subgroups of MSM. Results: A total of 4 601 MSM were involved in this study, with the following features presented as: aged 16-64 (28.38±7.11) years, proportions of residence from Guangzhou, Guangdong province or other provinces as 38.6%(1 776/4 601)、35.4%(1 629/4 601) and 26.0%(1 197/4 601), 59.6%(2 742/4 601) received bachelor or above degrees. 81.3%(3 741/4 601) of them claimed as having homosexual orientation. R values of risk level on very low risk, low risk level, moderate risk, high risk and very high risk appeared as 12.9%(594/4 601), 50.9%(2 342/4 601), 17.0%(783/4 601), 14.8%(682/4 601) and 4.3%(200/4 601), respectively. Scores of modifiable risk factors decreased year by year (P<0.05), among MSM in this study. In either of the groups that experiencing insertive or receptive sex, the ones with heterosexual orientation presented the highest scores of modifiable risk factors (P<0.05). Conclusions The risk levels on HIV infections called for special attention among the users of the self-evaluation network system. Among the MSM that carrying either insertive or receptive sex role, the ones with heterosexual orientation had the highest risk levels and scores of modifiable risk factors in Guangzhou. Further study should be explored to better understand the causes of related risks.