Longitudinal and spatial analysis of Americans' travel distances following COVID-19.

Travel has become less common due to COVID-19. While prior research has discussed recent travel changes for Americans in multiple ways, few have examined the adjusted travel that has been sustained since March 2021. In addition, little is known about changes in Americans' travel patterns in trips by distance. In this research, we asked two questions: 1) How have the numbers of trips by distance changed since 2019? and, 2) What are the geospatial patterns of the changes? Data from mid-March to mid-September 2021 indicates a 7% decrease in the number of trips and a 14.5% increase in people staying home. People traveled less except for those in the middle U.S. states, from North Dakota to Texas, as vertically aligned. Staying home more seemed to occur mainly in the South. Trips between 50 and 500 miles increased nationwide. COVID-19 has had different levels of impact on trips of different distance ranges.

Image sequence interpolation based on optical flow, segmentation, and optimal control.

When using motion fields to interpolate between two consecutive images in an image sequence, a major problem is to handle occlusions and disclusions properly. However, in most cases, one of both images contains the information that is either discluded or occluded; if the first image contains the information (i.e., the region will be occluded), forward interpolation shall be employed, while for information that is contained in the second image (i.e., the region will be discluded), one should use backward interpolation. Hence, we propose to improve an existing approach for image sequence interpolation by incorporating an automatic segmentation in the process, which decides in which region of the image forward or backward interpolation shall be used. Our approach is a combination of the optimal transport approach to image sequence interpolation and the segmentation by the Chan-Vese approach. We propose to solve the resulting optimality condition by a segregation loop, combined with a level set approach. We provide examples that illustrate the performance both in the interpolation error and in the human perception.

Impact of methadone on drug use and risky sex in China.

This study examined the impact of methadone on drug-using and risky sexual behaviors among 557 heroin injection drug users in one of the first methadone programs in China. Structured questionnaires were administered to collect data on methadone utilization, drug use, and risky sexual behaviors. Blood samples were tested for blood-borne infections. Multivariate logistic analyses revealed that, among opioid-addicted individuals, methadone participants were less likely to use or inject drugs and share needles than nonparticipants. They also were less likely to have multiple sexual partners or have unprotected sex. Those currently enrolled in methadone maintenance had lower risk of using and injecting drugs than those who were no longer receiving methadone. Data suggest positive, short-term impact on these important behaviors, but further studies are needed to examine the long-term impact of methadone treatment on disease rates.

[Factors associated with retention in a community-based methadone maintenance treatment among heroin addicts].

OBJECTIVE: To explore factors associated with retention in a community-based methadone maintenance treatment (MMT) among heroin addicts in Xichang of Sichuan province. METHODS: All 206 heroin addicts were first admitted to MMT community-based program between March to September 2004. Baseline data of patients characteristics, social function, drug using behaviors, sexual behaviors, dose of methadone and retention were collected. RESULTS: Up to Oct, 2005, all 206 patients contributed 8.98 +/- 5.74 person-months of following-up. The retention rates were 58.7% after 6 months and 34.6% after 12 months respectively. Cox proportional hazard regression model indicated that the employed (HR, 0.60; 95% CI, 0.39 - 0.92), helping family to do housework in past 30 days more than once a day (HR, 0.59; 95% CI, 0.42 - 0.82) and previous self-detoxification > or = 3 times (HR, 0.65; 95% CI, 0.47 - 0.91) were independently associated with retention. CONCLUSION: We should give individual counseling to help heroin addicts increasing compliance.

Nonfatal overdose among heroin users in southwestern China.

OBJECTIVE: To evaluate the prevalence of and risk factors for nonfatal overdose among heroin users in southwestern China. METHODS: In 2005, 731 heroin users in Sichuan Province, China were interviewed for overdose experiences in the past 12 months. Factors hypothesized to be associated with overdose were evaluated with logistic regression models. RESULTS: Eighty-eight (12%) drug users experienced at least one overdose, with a range from 1 to 20; 45 (51%) experienced 2 or more overdoses. Over half of participants with experience of overdose were recently released from prison (52%), and 56% used benzodiazepines before overdose. Longer methadone treatment in the past year (>or=180 vs. 0 days; OR, .3; 95% CI, .1-.8; P = .02), longer duration of using drugs (>or=7 vs. <7 years; OR, 2.2; 95% CI, 1.3-3.6; P = .002), and more frequency of injecting drugs in the past 3 months (>or=7 vs. <7 times/week; OR, 5.4; 95% CI, 3.2-9.0; P < .001) were independently associated with increased risk of nonfatal heroin overdose. CONCLUSIONS: Nonfatal heroin overdoses are common among Chinese heroin users. Drug users should be encouraged to participate and remain in methadone treatment to prevent overdose and be educated about proper response to overdose to reduce risk of overdose death.

Continued spread of HIV among injecting drug users in southern Sichuan Province, China.

OBJECTIVE: To estimate HIV prevalence among injecting drug users (IDUs) in a drug trafficking city in southwest Sichuan Province, China. METHODS: A total of 314 IDUs was invited to participate in the cross-sectional survey in 2004 through community outreach recruitment and peer referrals. Blood sample was taken for HIV antibody testing and a structured questionnaire was administered to collect information on socio-demographics, drug using and sexual behaviors. RESULTS: HIV prevalence among IDUs was 17.8% (56/314), about one half higher than that in previous survey in 2002 (11.3%, 43/379). Yi and other minority ethnicity (Odds ratio [OR], 3.1; 95% confidence interval [CI], 1.7-5.8; P < 0.001), and total times of sharing injecting equipment 1-9 times versus none, OR, 2.7; 95% CI 1.2-6.2; P = 0.02; and > or = 10 times versus none, OR, 7.5; 95% CI, 3.2-17.7; P < 0.001) were independent risk factors for HIV infection. CONCLUSION: IDUs with high prevalence rates of HIV and equipment sharing behavior in the drug trafficking city may serve a source for further spread of HIV to other areas in China. The increasing trend of HIV epidemic among IDUs underscores the urgency of scaling up interventions.

Incidence of HIV, hepatitis C and hepatitis B viruses among injection drug users in southwestern China: a 3-year follow-up study.

OBJECTIVE: To investigate the incidence rates of HIV, hepatitis C virus (HCV), and hepatitis B virus (HBV) among injection drug users (IDU) in a drug trafficking city in southwest China. DESIGN: A prospective cohort study. METHODS: A cohort of 333 HIV-seronegative IDU was followed for 36 months from November 2002 and evaluated every 6 months for seroconversions to HIV and HCV antibodies as well as hepatitis B surface antigen. Questionnaire interviews were conducted to collect information about risk behaviors. RESULTS: Some 68.8% of subjects completed the last follow-up survey. A total of 14 HIV, 47 HCV and 51 HBV seroconversions were observed over the 36-month follow-up period, yielding average incidence rates of 2.3 per 100 person-years for HIV, 33.3 for HCV and 11.3 for HBV. Multivariate Poisson regression analyses showed that factors independently associated with HIV seroconversion were minority ethnicity and greater frequent sharing of needles or syringes in the past 3 months one or more times per week. Predictors of HCV seroconversion included being female, greater frequent drug use in the past 3 months seven or more times per week, and frequent sharing of needles or syringes in the past 3 months one or more times per week. CONCLUSION: Blood-borne infections continue to spread, but at lower rates with time among IDU in a southwestern Chinese city where intervention programmes have existed for a few years. Rigorous implementation of harm reduction programmes may have reduced seroconversion to blood-borne infections among targeted high-risk populations.

[A prospective cohort study on human immunodeficiency virus and syphilis seroconversion among injecting drug users].

OBJECTIVE: To study the rate of human immunodeficiency virus (HIV) seroconversion, HIV transmission and related risk factors among injecting drug users (IDUs) in an area of Sichuan province. METHODS: In November 2002, a community-based baseline survey was conducted to recruit 333 HIV-seronegative IDUs for a prospective cohort study in Xichang county of Sichuan province, China. Follow-up visits were carried out every 6 months to study the situation of drug use, sexual behaviors of the IDUs and blood specimens were collected to test for antibodies against HIV and syphilis. RESULTS: During a 24-month follow-up period, cohort retention rate and HIV incidence were 75.7% and 2.53 per 100 person-years [95% confidence interval (CI): 1.10-3.97)], respectively. Multivariate Poisson regression model showed that risk factors which were significantly associated with HIV seroconversion would include: ethnicity (RR = 12.42; 95% CI: 2.72-56.74, P = 0.0012) and needle or syringe sharing in the past 3 months (RR = 4.06; 95% CI: 1.29-12.81, P = 0.0168). Syphilis seroconversion in this cohort was 4.71 per 100 person-years (95% CI: 2.59-6.82). In multivariate Poisson regression being female (RR = 4.42; 95% CI: 1.78-10.99, P = 0.0014) appeared to be the only factor which was significantly associated with syphilis seroconversion. CONCLUSION: Our study results showed that there was a rapid transmission of HIV and syphilis among IDUs in Sichuan province, suggesting that effective intervention should be urgently taken.

Syphilis among female sex workers in southwestern China: potential for HIV transmission.

OBJECTIVE: The objective of this study was to investigate the prevalence and risk factors of syphilis infection among female sex workers in a southwestern Chinese city along a drug trafficking route. METHODS: From December 2004 to January 2005, 343 female sex workers (FSWs) were recruited through community outreach and peer referring. Confidential questionnaire interviews were administered to collect information on sexual and other sexually transmitted diseases/HIV risk behaviors. Cervical and blood samples were collected to test for syphilis and HIV antibodies and Neisseria gonorrhoeae infection; Condyloma acuminatum infection was diagnosed clinically. RESULTS: Of 343 FSWs, 15.7% were infected with syphilis. The prevalence of HIV, gonorrhea, and C. acuminatum was 0.6%, 2.0%, and 1.5%, respectively. The subtype of 2 HIV-1 infections was both CRF 07BC. Nearly 10% of FSWs reported using illicit drugs. Consistent use, inconsistent use, and never use of condoms with commercial sex clients in the last month were reported by 53.9%, 38.5%, and 7.6% FSWs, respectively. Longer duration of sex work (odds ratio [OR] = 1.98; 95% confidence interval [CI] = 1.08-3.62), working at low-end establishments (OR = 2.03; 95% CI = 1.10-3.76), and if primary sex partners had sex with other women in the past 6 months (OR = 2.06; 95% CI = 1.08-3.91) were independently associated with syphilis infection. CONCLUSIONS: High prevalence of syphilis and overlapped unprotected commercial sex and drug using behaviors among FSWs along a drug-trafficking route may suggest a potential for rapid spread of HIV from injection drug users to FSWs and then to the general population and underscore the urgency of preventive interventions to break the bridge of FSWs for HIV/sexually transmitted disease spread.

Gender and HIV risk behavior among intravenous drug users in Sichuan Province, China.

Using data from a community-based study of injection drug users (IDUs) in Sichuan Province in China, this study compared the level of HIV risk behavior (needle sharing and unsafe sex) amongst female and male IDUs, and examined the risk factors separately for these two groups. Five risk factors were examined in the analysis, including a lack of family support, having an IDU primary sex partner, economic pressure, lack of access to a methadone program, and younger age. Regression results showed that male and female IDUs had different risk factors. For male IDUs, younger age and a lack of family support increased their level of HIV risk behavior. For female IDUs, having an IDU primary sex partner and economic pressure were predictive of their HIV risk behavior. Sex differences in risk factors are explained with respect to gender norms surrounding HIV risk behavior in the context of social relations. Female IDUs who were sex workers suffered additional HIV risk due to their powerlessness in negotiating safe sex with male customers. Practical implications of the findings for HIV/AIDS prevention and intervention work in China are discussed.

[Incidence rates of human immunodeficiency virus and syphilis as well as the rate of retention in a 6-month follow-up study of female sex workers in areas with heavy drug use in Xichang of Sichuan province, China].

OBJECTIVE: To investigate the human immunodeficiency virus (HIV) and syphilis incidence rates as well as the retention rate in a cohort with 6-month follow-up study among female sex workers (FSWs). METHODS: From December, 2004, to January, 2005, a community-based baseline survey was conducted to recruit 343 FSWs for a prospective cohort study in Xichang county of Sichuan province, China. Follow-up visits were conducted at 6 months to analyze risk factors associated with cohort retention for subjects' baseline sociodemographic and sexual behavioral characteristics. Blood specimens were also collected to test antibodies against HIV and syphilis. RESULTS: During the 6-month follow-up period, HIV and syphilis incidence appeared to be 1.00 per 100 person-years and 6.23 per 100 person-years, respectively. The rate of retention in the cohort was 53.6% (184/343). Results from multivariate logistic regression model showed that factors were significantly associated with cohort retention including people with minority ethnic background (OR = 0.36; 95% CI: 0.18-0.74), people having participated in AIDS prevention program (OR = 1.83; 95% CI: 1.17-2.86) or being clients in the last 6 months > or = 50 (OR = 1.75; 95% CI: 1.11-2.77) and having changed living/working place (OR = 0.56; 95% CI: 0.33-0.94). CONCLUSION: The results of this study showed that the syphilis incidence and unprotected sex behavior were high among local FSWs. People belonged to Han nationality, having participated in AIDS prevention program and having a steady living/working place were associated with cohort retention at 6-month follow-up study among FSWs, respectively.

HIV incidence and factors contributed to retention in a 12-month follow-up study of injection drug users in Sichuan Province, China.

HIV-1 seroconversion and subtype were evaluated, and factors associated with cohort retention were analyzed for subjects' baseline sociodemographic and behavioral characteristics in a 12-month follow-up study of injection drug users (IDUs). In November 2002, a community-based baseline survey was conducted to recruit 333 HIV-seronegative IDUs for a prospective cohort study in Xichang County of Sichuan Province, China. During the 12-month follow-up period, HIV incidence was 3.17 per 100 person-years (95% confidence interval [CI]: 0.98, 5.37), and all subtypes of 8 HIV-1 seroconversions were CRF_07BC. The retention rate at the 12-month follow-up visit was 70.3% (234 of 333 subjects). In a multiple logistic regression model, ethnicity (OR = 0.60, 95% CI: 0.34, 1.04) and appearing at the 6-month follow-up visit (OR = 9.03, 95% CI: 5.14, 15.89) were independently associated with retention. No drug-using or sexual behaviors were found to be associated with retention. This study confirmed one of drug-trafficking routes in mainland China, from Yunnan to Sichuan and then to Xinjiang. This study also suggested that HIV is spreading rapidly to more geographic areas along drug-trafficking routes in China, and a short-term follow-up rate may predict a long-term retention rate in this IDU cohort.

[Single nucleotide polymorphisms of HIV coreceptor CCR5 gene in Chinese Yi ethnic group and its association with HIV infection].

OBJECTIVE: To investigate the single nucleotide polymorphism (SNP) of HIV-1 coreceptor CCR5 gene in Chinese Yi ethnic group and the association between these SNPs and HIV/AIDS. METHODS: Peripheral blood samples of 102 HIV negative persons of Chinese Yi nationality, 87 males amd 15 females, aged 23 (12-37), and 68 HIV carriers, 61 males and 7 females, aged 27 (17-51). The regulatory and structural regions of the HIV coreceptor CCR5 gene were amplified from the genomic DNA by nested PCR, each of the two regions was divided into three gene fragments which were overlapped. High throughput DHPLC was used for screening of unknown mutations in each gene fragment. The PCR products showing different peak traces from wild types in DHPLC were sequenced by forward and reverse primers respectively. The sequences were analyzed with the help of Sequence Navigator software to search for SNP loci. Statistical analysis by SPSS and PPAP softwares were made to study the association between these SNPs and HIV infection. RESULTS: Five SNPs (A77G, G316A, T532C, C921T, and G668A) and a AGA deletion of the 686-688 nucleotides were discovered in the coding region of this gene in Chinese Yi ethnic group. C921T mutation was a nonsense mutation, and the other SNPs (A77G, G316A, T532C, and G668A) are sense mutation, with the amino acid changes of K26R, G106R, C178R, and R223Q. Only the frequency of R223Q allelic gene was high (0.08) but those of the others were low (less than 0.01). There was no significant difference in the allele frequency between the HIV negative and HIV positive groups (all P > 0.05). Five SNP loci (T58934G, G59029A, T59353C, G59402A, and C59653T) were found in the regulatory region of CCR5 gene with high allelic frequencies of 0.1912-0.2941. Between the HIV negative and HIV positive groups, there were no differences in the SNP loc (all P > 0.05). Statistical analysis of the association between the linkage of mutation loci with HIV infection suggested a significant difference in the haplotype frequency of T59353C-G59402A between the HIV negative and HIV positive groups of the Yi population. CONCLUSION: A high throughput screening method of detecting unknown genetic mutation DHPLC can effectively analyze the SNP of CCR5 regulatory and structural regions in Chinese Yi ethnic group.

[Community-based survey on human immunodeficiency virus infection among injection drug users in Sichuan, China].

OBJECTIVE: To investigate prevalence of human immunodeficiency virus (HIV) infection and risk factors for its transmission among injection drug users (IDUs) in Liangshan Yizu Autonomous Prefecture of Sichuan Province, China. METHODS: A community-based survey was conducted to investigate demographic characteristics, pattern and frequency of sharing injection equipment, and sexual behaviors in IDUs. Blood samples were also collected from them to detect for antibodies against HIV and syphilis. RESULTS: A total of 379 subjects were recruited with informed consent for study through community outreach and peer recruiting methods. Their prevalence of HIV infection was 11.3% (43/379). Ethnicity, frequency of sharing syringes and cotton swab during the past three months and syphilis infection associated with HIV infection by univariate analysis using chi-square test. Multivariate logistic regression analysis showed odds ratio of frequency of sharing syringes for HIV infection during the past three months was 2.28 (95% CI 1.18 - 4.43), and that for syphilis infection 3.10 (95% CI 1.48 - 6.48). CONCLUSION: Frequency of sharing syringes during the past three months associated with syphilis and HIV infection.

Community-based survey of HIV transmission modes among intravenous drug users in Sichuan, China.

GOAL: The goal of this study was to investigate the prevalence and different transmission risk factors of HIV among intravenous drug users (IDUs) in the Liangshan Yizu Autonomous Region of Sichuan province, China. METHODS: From November 8, 2002, to November 29, 2002, a community-based survey was conducted to investigate demographic characteristics, sharing patterns of injection equipment, frequencies of injection equipment, and sexual behaviors in IDUs. Blood samples were also collected to test for HIV and syphilis infection. A total of 379 subjects were recruited for the study through community outreach and peer recruiting methods. RESULTS: Of 379 IDUs, HIV prevalence was 11.3% (43 of 379). Ethnicity, total times of shared injection equipment in the past 3 months, shared cotton in the past 3 months, and syphilis infection were associated with HIV infection after univariate analysis using the chi-squared test. Multivariate logistic regression analysis showed total times of sharing injection equipment in the past 3 months (odds ratio [OR], 2.28; 95% confidence interval [CI], 1.18-4.43) and syphilis infection (OR, 3.10; 95% CI, 1.48-6.48) in the final model were independently associated with HIV prevalence. CONCLUSION: The results of this study suggested total times of sharing injection equipment in the past 3 months and syphilis infection were significantly associated with HIV infection. Further seroepidemiologic prospective cohort studies should be conducted to clarify the impact of syphilis and high-risk sexual behaviors on HIV transmission through unprotected sexual intercourse.

[Study on the relationship between hepatitis C virus infection and sharing injection equipment, sexual behavior among injecting drug users].

OBJECTIVE: To study hepatitis C virus (HCV) transmission through different modes of sharing injection equipment and sexual behavior among injecting drug users (IDUs) in Liangshan of Sichuan province. METHODS: A community-based survey was conducted to investigate past and current demographic data, injection equipment sharing patterns and sexual behavior of IDUs. Blood samples were also taken to test for HCV. The survey was conducted between Nov 8 and Nov 29, 2002. 379 subjects were screened through outreach recruitment and peer informing. SPSS (11.5) was used for data analysis. RESULTS: HCV prevalence was 71.0% (269/379). Needles or syringes sharing in the past three months and past syphilis infection were strongly associated with HCV transmission after univariate analysis using chi-square test. Trend analysis indicated that HCV infection rate increased along with the increase of needles or syringes sharing, sharing of rinse water and the number of peers sharing the equipments. Data from multivariate logistic regression showed that sharing of needles or syringes and history of syphilis infection were significantly associated with HCV transmission. No significant difference was found between HCV infection and sexual behavior after univariate analysis using chi-square test. CONCLUSION: Further sero-epidemiological prospective cohort studies should be conducted to clarify the relationship between different modes of sharing injection equipment, sexual behavior and HCV infection.

Community-based survey of HCV and HIV coinfection in injection drug abusers in Sichuan Province of China.

AIM: To investigate the prevalence and risk factors of HCV/HIV coinfection in injection drug abusers (IDAs) in Lianshan Yi Autonomous Prefecture of Sichuan province, China. METHODS: From November 8, 2002 to November 29, 2002, a community-based survey was conducted to investigate the demographic characteristics, patterns of shared injectors devices and sexual behaviors in IDAs. Blood samples were also collected to test HCV and HIV infection. A total of 379 subjects were recruited in the study through community outreach and peer recruiting methods. RESULTS: Of the 379 IDAs, the HCV prevalence and HIV prevalence were 71.0% and 11.3%, respectively, and HCV/HIV coinfection was 11.3%. HCV infection was found in 100% and 67.3% of HIV-positive and HIV-negative IDAs, respectively. HIV prevalence was 16.0% in HCV positive IDAs while none of the HCV negative IDAs was positive for HIV. Ethnicity, shared needles or syringes and cotton in the past 3 mo and syphilis infection were associated with HCV/HIV coinfection shown by univariate analysis using chi-square test. Multivariate logistic regression analysis showed that shared needles or syringes in the past 3 mo (Odds ratio=3.121, 95% CI: 1.278-7.617, P<0.05) and syphilis infection (Odds ratio=2.914, 95% CI: 1.327-6.398, P<0.01) were significantly associated with HCV infection. No statistically significant association was found in univariate analysis between sexual behaviors and HCV/HIV coinfection. CONCLUSION: Shared needles and syringes in the past 3 mo and syphilis infection were significantly associated with HCV infection. Further sero-epidemiological prospective cohort studies should be conducted to clarify the impact of syphilis and high risk sexual behaviors on HCV transmission through unprotected sexual intercourse.