Cocirculation and replacement of SARS-CoV-2 variants in crowded settings and marginalized populations along the US-Mexico border.

OBJECTIVE: To interrogate the circulating SARS-CoV-2 lin-eages and recombinant variants in persons living in migrant shelters and persons who inject drugs (PWID). MATERIALS AND METHODS: We combined data from two studies with marginalized populations (migrants in shelters and persons who inject drugs) in Tijuana, Mexico. SARS-CoV-2 variants were identified on nasal swabs specimens and compared to publicly available genomes sampled in Mexico and California. RESULTS: All but 2 of the 10 lineages identified were predomi-nantly detected in North and Central America. Discrepan-cies between migrants and PWID can be explained by the temporal emergence and short time span of most of these lineages in the region. CONCLUSION: The results illustrate the temporo-spatial structure for SARS-CoV-2 lineage dispersal and the potential co-circulation of multiple lineages in high-risk populations with close social contacts. These conditions create the potential for recombination to take place in the California-Baja California border.

Correlates of impulsivity among female sex workers in Mexico.

Impulsivity is a trait characteristic that is associated with sexual risk behavior. We examined correlates of impulsivity among 602 female sex workers (FSWs) enrolled in a sexual risk reduction intervention in Mexico (2016-2020). Impulsivity was positively associated with condomless sex with clients. Higher levels of impulsivity were associated with greater use of alcohol and heavy drugs, use of illicit drugs with clients, sexual/physical abuse history, and clinical depression. Global public health policy that supports free substance abuse treatment in combination with psychotherapeutic treatments (e.g. regulation management skills) and behavioral-focused therapy may help to reduce HIV/STI incidence in this vulnerable population.

Typologies and Correlates of Police Violence Against Female Sex Workers Who Inject Drugs at the México-United States Border: Limits of De Jure Decriminalization in Advancing Health and Human Rights.

Decriminalization of sex work is increasingly promoted as a structural measure to improve the health of vulnerable groups. In México, sex work is not illegal, but knowledge of policies' street-level impact is limited. This study describes typologies of police violence against female sex workers who inject drugs (FSWID), identifying risk and protective factors for violence exposure to inform policy responses. Survey data were collected during 2008-2010 among HIV-negative FSWID in a behavioral intervention in Tijuana and Ciudad Juarez (N = 584). Latent class analysis identified typologies of police violence in the past 6 months: asked for money, money taken, syringes taken, asked for sex, and sexually assaulted. Structural equation modeling (SEM) predicted latent class membership using sociodemographic, behavioral and risk environment factors, controlling for age, education, marital status, and city. Recent police violence was reported by 68% of FSWID, with three typologies emerging: Low (36.6%); Material (47.8%): having money/syringes taken or being asked for money; and Material/Sexual (15.7%): material violence and being asked for sex or sexually assaulted. In multivariable SEM, Material Violence was associated with: being jailed [adjusted Odds Ratio (aOR) = 4.34], HIV testing (aOR = 2.18), and trading sex indoors (aOR = 1.66). Factors associated with Material/Sexual Violence included: being jailed (aOR = 41.18), injecting with clients (aOR = 3.12), earning more money for sex without a condom (aOR = 2.88), being raped by a client (aOR = 2.13), drinking with clients (aOR = 2.03), receiving substance use treatment (aOR = 1.95), being <18 when first trading sex (aOR = .43), trading sex outdoors (aOR = .53), and poor working conditions (aOR = .56). Despite de jure decriminalization of sex work, police violence against FSWID at the México-United States border is pervasive with implications for sex- and drug-related harms. Closing gaps in policy implementation and mitigating material/sexual violence from police is imperative to decreasing economic vulnerability, risk of overdose and HIV, and improving engagement in HIV and harm reduction services.

A Randomized Controlled Trial of a Texting Intervention to Maintain Sexual Risk Reduction with Clients Among Female Sex Workers in Tijuana and Ciudad Juarez, Mexico.

Mobile phone technology may help sustain reductions in HIV/STI transmission risk behaviors among female sex workers (FSWs). We examined the efficacy of a text messaging intervention designed to maintain behavioral improvements in safer sex practices among 602 FSWs in Tijuana and Ciudad Juarez, Mexico. We hypothesized that FSWs who received brief risk reduction counseling and theory-based safer sex maintenance text messages over a 24-month period would have fewer incident HIV/STIs and report greater maintenance of safer sex practices compared to FSWs who received counseling and texts on maintaining general health. Theory-based texts did not change the odds of becoming infected with HIV/STIs in either study site. However, they did lead to significant, sustained protected sex in Tijuana. Theory-based text messaging interventions may help sustain reductions in sexual risk behavior among FSWs.Trial Registration Clinical Trials.gov. Identifier: NCT02447484.

Hazardous Alcohol Consumption Moderates the Relationship Between Safer Sex Maintenance Strategies and Condomless Sex With Clients Among Female Sex Workers in Mexico.

Understanding the relationship between cognitive and behavioral processes and long-term behavior change is critical to developing behavior change maintenance interventions. We examined the relationship between cognitive and behavioral safer sex maintenance strategies and condomless vaginal/anal sex with clients among female sex workers (FSWs) in Mexico. We hypothesized a moderating effect of hazardous alcohol use, such that the relationship between the use of safer sex maintenance strategies and condomless sex would be weaker among FSWs who meet criteria for hazardous alcohol consumption. Data were gathered from 602 FSWs enrolled in a sexual risk reduction intervention with a text messaging maintenance component. Seven cognitive and behavioral strategies purported to be critical in sustaining long-term behavior change were measured (e.g., maintenance self-efficacy). The relationship between FSWs' use of safer sex maintenance strategies and condomless vaginal/anal sex with clients was moderated by hazardous alcohol consumption. The association was weaker among FSWs who met criteria for hazardous alcohol consumption. Among FSWs who met criteria for hazardous alcohol consumption, maintenance self-efficacy was associated with fewer condomless sex acts with clients (b = -0.35, p < .001). Among FSWs who did not meet criteria for hazardous alcohol consumption, recovery self-efficacy (b = -0.21, p < .05) and self-monitoring (b = -0.34, p < .001) were associated with fewer acts of condomless sex. Results indicate the importance of examining the multidimensional nature of safer sex maintenance strategies and of exploring subgroup differences in their associations with behavioral outcomes. Interventions that address safer sex maintenance strategies in the context of alcohol treatment should be developed for this subgroup of FSWs.

The Relationship Between Educational Attainment and Health Care Access and Use Among Mexicans, Mexican Americans, and U.S.-Mexico Migrants.

The aim of the study was to assess the relationship between educational attainment and health care access and use among Mexican-origin populations. Data from the 2012 Mexican National Health and Nutrition Study, the 2013 Project Migrante Health Care Access and Utilization Survey, and the 2013-2014 California Health Interview Survey were used to examine educational gradients in health insurance, medical home, and hospitalization among Mexicans in Mexico, northbound, southbound, and deported migrants, and U.S.-and foreign-born Mexican Americans. College graduates had greater odds of being insured relative to those with less than a high school degree among Mexicans (AOR = 1.48, p < 0.001), northbound migrants (AOR = 3.69, p < 0.001), and the foreign-born (AOR = 2.01, p < 0.01), and of having a medical home among Mexicans (AOR = 1.95, p < 0.001) and the foreign-born (AOR = 2.14, p < 0.05). Eliminating differences by educational attainment in the U.S. will require policy changes like making immigrants eligible for public insurance. In Mexico, it will require targeted outreach to enroll underserved populations in existing public insurance programs.

Maternal role strain and depressive symptoms among female sex workers in Mexico: the moderating role of sex work venue.

Stressors that arise in parenting are likely to have an adverse impact on the psychological well-being of female sex workers (FSWs), particularly in low- to middle-income countries (LMIC). This study examined the association between maternal role strain and depressive symptoms among 426 FSW mothers with dependent-age children (aged < 18 years) in Tijuana and Cd. Juarez, Mexico (2016-2017). Four dimensions of maternal role strain (e.g., child emotional and behavioral problems) were examined in relation to maternal depressive symptoms. We also investigated whether the relationship between maternal role strain and depressive symptoms was modified by venue of sex work. Compared to indoor/establishment-based FSWs, street-based FSWs reported significantly more child-related financial strain. In multiple regression analysis, having more depressive symptoms was associated with identifying as a street-based FSW, greater use of drugs, lower emotional support, more child-related financial strain and more emotional and behavioral problems in children. A significant interaction was identified such that the association between maternal role strain and depressive symptoms was stronger for indoor/establishment-based compared to street-based FSWs. These findings suggest the need to address parenting strain and type of sex work venue in the development of counseling programs to improve the mental health of FSWs in LMIC.

"Somebody Is Gonna Be Hurt": Involuntary Drug Treatment in Mexico.

Involuntary drug treatment (IDT) is ineffective in decreasing drug use, yet it is a common practice. In Mexico, there are not enough professional residential drug treatment programs, and both voluntary and involuntary drug treatment is often provided by non-evidence based, non-professional programs. We studied the experiences of people who inject drugs (PWID) in Tijuana who were taken involuntarily to drug centers under the auspices of a federally funded police operation. We provide insight into how the health, wellbeing, human rights, dignity, and security of PWID ought to be at the center of international drug policies included in universal health care systems.

Impact of time perspectives on texting intervention to reduce HIV/STI transmission among female sex workers in Tijuana and Ciudad Juarez, Mexico.

Text messages may sustain post-counseling gains in behavioral improvements and reduce HIV/STI incidence. However, their effectiveness may depend on the messages' time perspective and characteristics of the individual. We evaluated the impact of time perspective on a text messaging intervention designed to maintain improvements in safer sex practices among drug-using and non-drug-using female sex workers (FSWs) in Tijuana (n = 141) and Cd. Juarez (n = 129), Mexico. FSWs received the efficacious Mujer Segura intervention, and were randomized to receive safer sex maintenance text messages with either a short-term or future-oriented time perspective. The outcome was HIV/STI incidence rate over 6-month follow-up. In Tijuana, combined HIV/STI incidence density was lower among FSWs in the FUTURE group (31.67 per 100 py) compared to women in the SHORT-TERM group (62.40 per 100 py). Conversely, in Cd. Juarez, HIV/STI incidence density was lower (although non-significant) among FSWs in the SHORT-TERM group (19.80 per 100 py) compared to those in the FUTURE group (35.05 per 100 py). These findings suggest that future-oriented text messages may sustain post-counseling improvements in sexual risk behavior among FSWs, but findings may vary by FSWs' characteristics (e.g., drug use), and by region and context.

Intimate Partner Violence Among Female Sex Workers and Their Noncommercial Male Partners in Mexico: A Mixed-Methods Study.

Utilizing mixed methods, we examined intimate partner violence (IPV) behaviors among 428 female sex workers (FSWs) who use drugs and their noncommercial male partners in Tijuana and Ciudad Juarez, Mexico. Half of all participants reported perpetrating and experiencing at least one type of IPV behavior in the past year. In interviews, drug use emerged as an important theme associated with IPV behaviors, and we found men and women differed in their motivations for engaging in IPV behaviors. Findings highlight how gender and power are interlinked with and may exacerbate drug use and IPV behaviors among marginalized populations.

Changes in Condom Use Over Time Among Female Sex Workers and Their Male Noncommercial Partners and Clients.

Female sex workers (FSWs) often report inconsistent condom use with clients and noncommercial male partners, yet changes in condom use with various partner types during participation in observation studies remains underexplored. This longitudinal study of 214 FSWs and their male, noncommercial partners in the Mexico-U.S. border region, where HIV prevalence among FSWs continues to be high, utilized negative binomial regressions to examine changes in condom use with intimate partners and clients (regular and nonregular) over 24 months. Condom use decreased over time among couples in Ciudad Juarez, but there was no change in condom use among couples in Tijuana. FSWs' condom use with regular and nonregular clients significantly increased over time, which is consistent with previous research finding behavioral changes when participating in observational studies. Findings suggest the need for continued efforts to promote condom use among FSWs and their noncommercial male partners in addition to clients.

Cost-Effectiveness of Combined Sexual and Injection Risk Reduction Interventions among Female Sex Workers Who Inject Drugs in Two Very Distinct Mexican Border Cities.

BACKGROUND: We evaluated the cost-effectiveness of combined single session brief behavioral intervention, either didactic or interactive (Mujer Mas Segura, MMS) to promote safer-sex and safer-injection practices among female sex workers who inject drugs (FSW-IDUs) in Tijuana (TJ) and Ciudad-Juarez (CJ) Mexico. Data for this analysis was obtained from a factorial RCT in 2008-2010 coinciding with expansion of needle exchange programs (NEP) in TJ, but not in CJ. METHODS: A Markov model was developed to estimate the incremental cost per quality adjusted life year gained (QALY) over a lifetime time frame among a hypothetical cohort of 1,000 FSW-IDUs comparing a less intensive didactic vs. a more intensive interactive format of the MMS, separately for safer sex and safer injection combined behavioral interventions. The costs for antiretroviral therapy was not included in the model. We applied a societal perspective, a discount rate of 3% per year and currency adjusted to US$2014. A multivariate sensitivity analysis was performed. The combined and individual components of the MMS interactive behavioral intervention were compared with the didactic formats by calculating the incremental cost-effectiveness ratios (ICER), defined as incremental unit of cost per additional health benefit (e.g., HIV/STI cases averted, QALYs) compared to the next least costly strategy. Following guidelines from the World Health Organization, a combined strategy was considered highly cost-effective if the incremental cost per QALY gained fell below the gross domestic product per capita (GDP) in Mexico (equivalent to US$10,300). FINDINGS: For CJ, the mixed intervention approach of interactive safer sex/didactic safer injection had an incremental cost-effectiveness ratio (ICER) of US$4,360 ($310-$7,200) per QALY gained compared with a dually didactic strategy. Using the dually interactive strategy had an ICER of US$5,874 ($310-$7,200) compared with the mixed approach. For TJ, the combination of interactive safer sex/didactic safer injection had an ICER of US$5,921 ($104-$9,500) per QALY compared with dually didactic. Strategies using the interactive safe injection intervention were dominated due to lack of efficacy advantage. The multivariate sensitivity analysis showed a 95% certainty that in both CJ and TJ the ICER for the mixed approach (interactive safer sex didactic safer injection intervention) was less than the GDP per capita for Mexico. The dual interactive approach met this threshold consistently in CJ, but not in TJ. INTERPRETATION: In the absence of an expanded NEP in CJ, the combined-interactive formats of the MMS behavioral intervention is highly cost-effective. In contrast, in TJ where NEP expansion suggests that improved access to sterile syringes significantly reduced injection-related risks, the interactive safer-sex combined didactic safer-injection was highly cost-effective compared with the combined didactic versions of the safer-sex and safer-injection formats of the MMS, with no added benefit from the interactive safer-injection component.

Measuring Current Drug Use in Female Sex Workers and Their Noncommercial Male Partners in Mexico: Concordance Between Data Collected From Surveys Versus Semi-Structured Interviews.

BACKGROUND: Self-reports are commonly used to assess prevalence and frequency of drug use, but it is unclear whether qualitative methods like semi-structured interviews are as useful at obtaining such information as quantitative surveys. OBJECTIVES: This study compared drug use occurrence and frequency using data collected from quantitative surveys and qualitative interviews. We also examined whether combining data from both sources could result in significant increases in percentages of current users and whether the concordance between the two sets of data was associated with the type of drug use, age, gender and socioeconomic status. METHODS: Self- reports of recent marijuana, heroin, crack, cocaine, crystal/methamphetamine, inhalant, and tranquilizer use were collected using both methods from a cohort of Mexican female sex workers and their non-commercial male partners (n = 82). RESULTS: Participants were significantly less likely to report marijuana, cocaine and tranquilizer use and frequency of use during the qualitative interviews than during the quantitative surveys. Agreement on frequency of drug use was excellent for crystal/methamphetamine, heroin and inhalant use, and weak for cocaine, tranquilizers and marijuana use. Older participants exhibited significantly higher concordance than younger participants in reports of marijuana and methamphetamine use. Higher monthly income was significantly associated with higher concordance in crack use but lower concordance with marijuana use. CONCLUSIONS: Although use of such data can result in an underreporting of drug use, qualitative data can be quantified in certain circumstances to triangulate and confirm the results from quantitative analyses and provide a more comprehensive view of drug use.

HIV Prevention Among Mexican Migrants at Different Migration Phases: Exposure to Prevention Messages and Association With Testing Behaviors.

Mobile populations are at increased risk for HIV infection. Exposure to HIV prevention messages at all phases of the migration process may help decrease im/migrants' HIV risk. We investigated levels of exposure to HIV prevention messages, factors associated with message exposure, and the association between exposure to prevention messages and HIV testing behavior among Mexican im/migrants at different phases of the migration process. We conducted a cross-sectional, probability survey of Mexican im/migrants (N = 3,149) traveling through the border city of Tijuana, Mexico. The results indicate limited exposure to prevention messages (57-75%) and suboptimal last 12-month HIV testing rates (14-25%) across five migration phases. Compared to pre-departure levels (75%), exposure to messages decreases at all post-departure migration phases (57-63%, p < .001). In general, exposure to prevention messages is positively associated with greater odds of HIV testing at the pre-departure, destination, and interception phases. Binational efforts need to be intensified to reach and deliver HIV prevention to Mexican im/migrants across the migration continuum.

Love, Trust, and HIV Risk Among Female Sex Workers and Their Intimate Male Partners.

OBJECTIVES: We examined correlates of love and trust among female sex workers and their noncommercial male partners along the Mexico-US border. METHODS: From 2011 to 2012, 322 partners in Tijuana and Ciudad Juárez, Mexico, completed assessments of love and trust. Cross-sectional dyadic regression analyses identified associations of relationship characteristics and HIV risk behaviors with love and trust. RESULTS: Within 161 couples, love and trust scores were moderately high (median 70/95 and 29/40 points, respectively) and correlated with relationship satisfaction. In regression analyses of HIV risk factors, men and women who used methamphetamine reported lower love scores, whereas women who used heroin reported slightly higher love. In an alternate model, men with concurrent sexual partners had lower love scores. For both partners, relationship conflict was associated with lower trust. CONCLUSIONS: Love and trust are associated with relationship quality, sexual risk, and drug use patterns that shape intimate partners' HIV risk. HIV interventions should consider the emotional quality of sex workers' intimate relationships.

"Amar te Duele" ("love hurts"): sexual relationship power, intimate partner violence, depression symptoms and HIV risk among female sex workers who use drugs and their non-commercial, steady partners in Mexico.

A significant body of research among female sex workers (FSWs) has focused on individual-level HIV risk factors. Comparatively little is known about their non-commercial, steady partners who may heavily influence their behavior and HIV risk. This cross-sectional study of 214 FSWs who use drugs and their male steady partners aged ≥18 in two Mexico-U.S. border cities utilized a path-analytic model for dyadic data based upon the Actor-Partner Interdependence Model to examine relationships between sexual relationship power, intimate partner violence (IPV), depression symptoms, and unprotected sex. FSWs' relationship power, IPV perpetration and victimization were significantly associated with unprotected sex within the relationship. Male partners' depression symptoms were significantly associated with unprotected sex within the relationship. Future HIV prevention interventions for FSWs and their male partners should address issues of sexual relationship power, IPV, and mental health both individually and in the context of their relationship.

Correlates of unprotected sex by client type among female sex workers that inject drugs in Tijuana and Ciudad Juarez, Mexico.

AIMS: Risk environment factors may influence unprotected sex between female sex workers who are also injection drug users (FSW-IDUs) and their regular and non-regular clients differently. Our objective is to identify correlates of unprotected vaginal sex in the context of client type. METHODS: A cross-sectional survey of 583 FSW-IDUs in Tijuana and Ciudad Juarez, Mexico, was analyzed using negative binomial regression to determine physical, social, economic, and policy risk-environment factors that affect the frequency of unprotected sex with regular and non-regular clients. RESULTS: Median number of unprotected vaginal sex acts in the past month among FSW-IDUs and their regular and non-regular clients was 11 (IQR 3-30) and 13 (IQR 5-30), respectively. Correlates differed by site and client type and were most closely associated with the risk environment. In Tijuana, social factors (e.g., injecting drugs with clients) were independently associated with more unprotected sex. Factors independently associated with less unprotected sex across client type and site included social and economic risk environment factors (e.g., receiving more money for unprotected sex). In the policy risk environment, always having free access to condoms was independently associated with less unprotected sex among non-regular clients in Tijuana (Risk rate ratio = 0.64; 95% confidence interval 0.43-0.97). CONCLUSIONS: Primarily physical, social, and economic risk-environment factors were associated with unprotected vaginal sex between FSW-IDUs and both client types, suggesting potential avenues for intervention.

Healthcare access among circular and undocumented Mexican migrants: results from a pilot survey on the Mexico-US border.

BACKGROUND: Temporary and unauthorized migrants may face unique obstacles to access health care services in the U.S. OBJECTIVE: This study estimated levels of health care access among Mexican migrants returning to Mexico from the U.S. and factors associated with access to health care, with emphasis on the role of modifiable, enabling factors. METHODS: We conducted a pilot probability health care survey of migrants in the border city of Tijuana, Mexico (N=186). RESULTS: Approximately 42% of migrants reported having used health care services in the U.S. during the past year. Only 38% had a usual source of care and approximately 11% went without needed medical care in the U.S. About 71% of migrants did not have health insurance in the U.S. Lack of health insurance and transportation limitations were significantly related to various access indicators. CONCLUSION: These results have implications for future policies and programs aimed to address modifiable health care access barriers faced by these vulnerable and underserved segments of the Mexican migrant population.

Rethinking risk: gender and injection drug-related HIV risk among female sex workers and their non-commercial partners along the Mexico-U.S. border.

BACKGROUND: Studies of injection drug-using couples suggest a gendered performance of risk in which men exert greater control over drug use and render their female partners vulnerable to HIV infection and other negative health outcomes. This study assesses gender roles in injection drug use as practiced among female sex workers and their intimate male partners within a risk environment marked by rapid socioeconomic changes. METHODS: We draw on quantitative surveys, semi-structured interviews, and ethnographic fieldwork conducted as part of cohort study of HIV/STI risk among female sex workers and their intimate, non-commercial partners along the Mexico-U.S. border. This study employed descriptive statistics and inductive analyses of transcripts and field notes to examine practices related to drug procurement, syringe sharing, and injection assistance among couples in which both partners reported injecting drugs in the past 6 months. RESULTS: Among 156 couples in which both partners injected drugs (n=312), our analyses revealed that women's roles in drug use were active and multidimensional, and both partners' injection risk practices represented embodied forms of cooperation and compassion. Women often earned money to purchase drugs and procured drugs to protect their partners from the police. Sharing drugs and syringes and seeking injection assistance were common among couples due to drug market characteristics (e.g., the use of "black tar" heroin that clogs syringes and damages veins). Both women and men provided and received injection assistance, which was typically framed as caring for the partner in need of help. CONCLUSION: Our mixed methods study suggests that in certain risk environments, women are more active participants in injection-related practices than has often been revealed. This participation is shaped by dynamic relationship and structural factors. Our suggestion to consider gendered injection risk as a nuanced and relational process has direct implications for future research and interventions.

Prevalence and correlates of HIV and sexually transmitted infections among female sex workers and their non-commercial male partners in two Mexico-USA border cities.

Female sex workers (FSWs) acquire HIV and other sexually transmitted infections (STIs) through unprotected sex with commercial and non-commercial (intimate) male partners. Little research has focused on FSWs' intimate relationships, within which condom use is rare. We sought to determine the prevalence and correlates of HIV/STIs within FSWs' intimate relationships in Northern Mexico. From 2010 to 2011, we conducted a cross-sectional survey of FSWs and their non-commercial male partners in Tijuana and Ciudad Juárez, Mexico. Eligible FSWs and their verified male partners were aged ≥18 years; FSWs reported lifetime use of heroin, cocaine, crack, or methamphetamine and recently exchanged sex (past month). Participants completed baseline questionnaires and testing for HIV, chlamydia, gonorrhea, and syphilis. We determined the prevalence and correlates of individuals' HIV/STI positivity using bivariate probit regression. Among 212 couples (n = 424), prevalence of HIV was 2.6 % (n = 11). Forty-two (9.9 %) tested positive for any HIV/STIs, which was more prevalent among women than men (12.7 % vs. 7.1 %, p < 0.05). FSWs with regular sex work clients were less likely to test positive for HIV/STIs than those without regular clients. Similarly, male partners of FSWs who had regular clients were 9 % less likely to have HIV/STIs. Higher sexual decision-making power was protective against HIV/STIs for women. Men who recently used methamphetamine or reported perpetrating any conflict within steady relationships were more likely to test positive for HIV/STIs. Within FSWs' intimate relationships in two Mexican-US border cities, nearly one in ten partners tested positive for HIV/STIs. Couple-based prevention interventions should recognize how intimate relationship factors and social contexts influence HIV/STI vulnerability.