Mathematical modeling of hepatitis c virus (HCV) prevention among people who inject drugs: A review of the literature and insights for elimination strategies

Network-based strategies to combat HCV: Examining social and spatial drivers of transmission among PWID in New Delhi

People who inject drugs (PWID) account for some of the fastest-growing HCV epidemics globally. While individual risk factors for infection are understood, less is known about network and spatial factors critical for elimination strategies. Two thousand five hundred twelve PWID in New Delhi, India, were recruited (2017-19) through network referrals. Biometrics identified duplicates and cross-network linkages. Participants completed semi-annual surveys and blood tests for HCV antibodies and RNA. Poisson regression and network analyses identified predictors of incident HCV and compared network-based intervention approaches. Baseline HCV antibody prevalence was 65.1%, of whom 79.6% were HCV RNA-positive. We observed 92 HCV seroconversions over 382.25 person-years (incidence: 24.1 per 100 person-years). Of the 92 seroconverters, 67% (62) were directly connected to an RNA-positive participant, and all were within one degree of separation from an RNA-positive participant. Individual-level factors associated with seroconversion included age, sexual activity, and injection behaviours. After adjusting for individual-level factors, seroconversion was significantly associated with number of RNA-positive partners (adjusted incidence rate ratio [AIRR] = 1.30) and injecting at a particular venue (AIRR = 2.53). This association extended to indirect ties, with 17% reduced odds of seroconversion for each degree of separation from the venue (AIRR = 0.83). Network analyses comparing intervention strategies found that targeting venues identified more cases compared to a treat-a-friend approach. We observed a fast-growing HCV epidemic driven by viremia within individuals' immediate networks and indirect social and spatial ties, demonstrating the importance of achieving broad, sustained virologic response and rethinking network-based interventions to include venues.

Potential impact of curative and preventive interventions toward hepatitis C elimination in people who inject drugs-A network modeling study

BACKGROUND

Injection-equipment-sharing networks play an important role in hepatitis C virus (HCV) transmission among people who inject drugs (PWID). Direct-acting antiviral (DAA) treatments for HCV infection and interventions to prevent HCV transmission are critical components of an overall hepatitis C elimination strategy, but how they contribute to the elimination outcomes in different PWID network settings are unclear.

METHODS

We developed an agent-based network model of HCV transmission through the sharing of injection equipment among PWID and parameterized and calibrated the model with rural PWID data in the United States. We modeled curative and preventive interventions at annual coverage levels of 12.5 %, 25 %, or 37.5 % (cumulative percentage of eligible individuals engaged), and two allocation approaches: random vs targeting PWID with more injection partners (hereafter 'degree-based'). We compared the impact of these intervention strategies on prevalence and incidence of HCV infections. We conducted sensitivity analysis on key parameters governing the effects of curative and preventive interventions and PWID network characteristics.

RESULTS

Combining curative and preventive interventions at 37.5 % annual coverage with degree-based allocation decreased prevalence and incidence of HCV infection by 67 % and 70 % over two years, respectively. Curative interventions decreased prevalence by six to 12 times more than preventive interventions, while curative and preventive interventions had comparable effectiveness on reducing incidence. Intervention impact increased with coverage almost linearly across all intervention strategies, and degree-based allocation was always more effective than random allocation, especially for preventive interventions. Results were sensitive to parameter values defining intervention effects and network mean degree.

CONCLUSION

DAA treatments are effective in reducing both prevalence and incidence of HCV infection in PWID, but preventive interventions play a significant role in reducing incidence when intervention coverage is low. Increasing coverage, including efforts in reaching individuals with the most injection partners, preventing reinfection, and improving compliance and retention in preventive services can substantially improve the outcomes. PWID network characteristics should be considered when designing hepatitis C elimination programs.

Hepatitis C screening in Lithuania: first-year results and scenarios for achieving WHO elimination targets

BACKGROUND

The World Health Organization (WHO) has outlined a set of targets to achieve eliminating hepatitis C by 2030. In May 2022, Lithuanian health authorities initiated a hepatitis C virus (HCV) screening program to start working towards elimination. In the program, bonus was given to general practitioners (GPs) to promote and conduct anti-HCV tests for two situations: (1) one time testing for individuals born in 1945-1994 and (2) annual HCV testing for persons who inject drugs or are living with human immunodeficiency virus (HIV) regardless of age. This study aimed to model the current viral hepatitis C epidemiological status in Lithuania and to outline the requirements for WHO elimination targets using the first-year HCV screening results.

METHODS

Individuals were invited to participate in the anti-HCV screening by GPs during routine visits. Patients who tested positive were then referred to a gastroenterologist or infectious disease doctor for further confirmatory testing. If a patient received a positive RNA test and a fibrosis staging result of ≥ F2, the doctor prescribed direct-acting antivirals. Information on the patients screened, diagnosed, and treated was obtained from the National Health Insurance Fund. The Markov disease progression model, developed by the CDA Foundation, was used to evaluate the screening program results and HCV elimination progress in Lithuania.

RESULTS

Between May 2022 and April 2023, 790,070 individuals underwent anti-HCV testing, with 11,943 individuals (1.5%) receiving positive results. Anti-HCV seroprevalence was found to be higher among males than females, 1.9% and 1.2%, respectively. Within the risk population tested, 2087 (31.1%) seropositive individuals were identified. When comparing the screening program results to WHO elimination targets through modelling, 2180 patients still need to be treated annually until 2030, along with expanding fibrosis restrictions. If an elimination approach was implemented, 1000 new infections would be prevented, while saving 150 lives and averting 90 decompensated cirrhosis cases and 110 hepatocellular carcinoma cases.

CONCLUSIONS

During the first year of the Lithuanian screening program, GPs were able to screen 44% of the target population. However, the country will not meet elimination targets as it currently stands without increasing treatment levels and lifting fibrosis restrictions.

Direct-acting antiviral therapies for hepatitis C infection: global registration, reimbursement, and restrictions

Direct-acting antivirals (DAAs) for hepatitis C virus (HCV) infection have delivered high response rates (>95%) and simplified the management of HCV treatment, permitting non-specialists to manage patients without advanced liver disease. We collected and reviewed global data on the registration and reimbursement (government subsidised) of HCV therapies, including restrictions on reimbursement. Primary data collection occurred between Nov 15, 2021, and July 24, 2023, through the assistance of a global network of 166 HCV experts. We retrieved data for 160 (77%) of 209 countries and juristrictions. By mid-2023, 145 (91%) countries had registered at least one of the following DAA therapies: sofosbuvir-velpatasvir, sofosbuvir-velpatasvir-voxilaprevir, glecaprevir-pibrentasvir, sofosbuvir-daclatasvir, or sofosbuvir. 109 (68%) countries reimbursed at least one DAA therapy. Among 102 low-income and middle-income countries (LMICs), 89 (87%) had registered at least one HCV DAA therapy and 53 (52%) reimbursed at least one DAA therapy. Among all countries with DAA therapy reimbursement (n=109), 66 (61%) required specialist prescribing, eight (7%) had retreatment restrictions, seven (6%) had an illicit drug use restriction, five (5%) had an alcohol use restriction, and three (3%) had liver disease restrictions. Global access to DAA reimbursement remains uneven, with LMICs having comparatively low reimbursement compared with high-income countries. To meet WHO goals for HCV elimination, efforts should be made to assist countries, particularly LMICs, to increase access to DAA reimbursement and remove reimbursement restrictions-especially prescriber-type restrictions-to ensure universal access.

Impact of voluntary testing on infectious disease epidemiology: A game theoretic approach

The World Health Organization recommends test-and-treat interventions to curb and even eliminate epidemics of HIV, viral hepatitis, and sexually transmitted infections (e.g., chlamydia, gonorrhea, syphilis and trichomoniasis). Epidemic models show these goals are achievable, provided the participation of individuals in test-and-treat interventions is sufficiently high. We combine epidemic models and game theoretic models to describe individual's decisions to get tested for infectious diseases within certain epidemiological contexts, and, implicitly, their voluntary participation to test-and-treat interventions. We develop three hybrid models, to discuss interventions against HIV, HCV, and sexually transmitted infections, and the potential behavioral response from the target population. Our findings are similar across diseases. Particularly, individuals use three distinct behavioral patterns relative to testing, based on their perceived costs for testing, besides the payoff for discovering their disease status. Firstly, if the cost of testing is too high, then individuals refrain from voluntary testing and get tested only if they are symptomatic. Secondly, if the cost is moderate, some individuals will test voluntarily, starting treatment if needed. Hence, the spread of the disease declines and the disease epidemiology is mitigated. Thirdly, the most beneficial testing behavior takes place as individuals perceive a per-test payoff that surpasses a certain threshold, every time they get tested. Consequently, individuals achieve high voluntary testing rates, which may result in the elimination of the epidemic, albeit on temporary basis. Trials and studies have attained different levels of participation and testing rates. To increase testing rates, they should provide each eligible individual with a payoff, above a given threshold, each time the individual tests voluntarily.

Reducing barriers to the hepatitis C care cascade in prison via point-of-care RNA testing: a qualitative exploration of men in prison using an integrated framework

BACKGROUND AND AIMS

Hepatitis C virus (HCV) is highly prevalent within the prison setting. Although HCV testing and treatment are available within prisons, system barriers can impede progress along the HCV care cascade for those who are incarcerated. The PIVOT intervention used a 'one-stop-shop' model (i.e. point-of-care HCV RNA testing, Fibroscan-based liver disease assessment and treatment) at a reception prison in New South Wales, Australia. This analysis sought to understand the role of point-of-care HCV RNA testing at intake in reducing barriers to the HCV care cascade within the male prison setting.

DESIGN AND SETTING

Qualitative analysis using semi-structured interviews in a reception prison in Australia.

PARTICIPANTS

Twenty-four men enrolled in the PIVOT study; all participants had undergone HCV point-of-care testing in the intervention arm.

MEASUREMENTS

Høj's Integrated Framework informed this analysis.

FINDINGS

Participants widely expressed the view that point-of-care HCV RNA testing on entry was beneficial for care engagement. Point-of-care testing was perceived as timely (compared with standard pathology) and reduced opportunities for adjudication by correctional officers due to fewer clinic visits for testing and results. Adoption of routine opt-out testing at prison intake was regarded as an important strategy for normalising HCV testing (and likely to increase pathways to treatment uptake) and fostered patient candidacy (i.e. self-perceived eligibility to access care).

CONCLUSION

Twenty-four men in prison in New South Wales, Australia, who underwent opt-out point-of-care HCV RNA testing on entry into prison, widely supported the programme as a means of overcoming barriers to HCV testing and treatment in the prison setting, as well as providing public health benefits through early detection of HCV infection among people entering into custody.

Public health interventions, priority populations, and the impact of COVID-19 disruptions on hepatitis C elimination among people who have injected drugs in Montreal (Canada): A modeling study

BACKGROUND

In Montreal (Canada), high hepatitis C virus (HCV) seroincidence (21 per 100 person-years in 2017) persists among people who have injected drugs (PWID) despite relatively high testing rates and coverage of needle and syringe programs (NSP) and opioid agonist therapy (OAT). We assessed the potential of interventions to achieve HCV elimination (80% incidence reduction and 65% reduction in HCV-related mortality between 2015 and 2030) in the context of COVID-19 disruptions among all PWID and PWID living with HIV.

METHODS

Using a dynamic model of HCV-HIV co-transmission, we simulated increases in NSP (from 82% to 95%) and OAT (from 33% to 40%) coverage, HCV testing (every 6 months), or treatment rate (100 per 100 person-years) starting in 2022 among all PWID and PWID living with HIV. We also modeled treatment scale-up among active PWID only (i.e., people who report injecting in the past six months). We reduced intervention levels in 2020-2021 due to COVID-19-related disruptions. Outcomes included HCV incidence, prevalence, and mortality, and proportions of averted chronic HCV infections and deaths.

RESULTS

COVID-19-related disruptions could have caused temporary rebounds in HCV transmission. Further increasing NSP/OAT or HCV testing had little impact on incidence. Scaling-up treatment among all PWID achieved incidence and mortality targets among all PWID and PWID living with HIV. Focusing treatment on active PWID could achieve elimination, yet fewer projected deaths were averted (36% versus 48%).

CONCLUSIONS

HCV treatment scale-up among all PWID will be required to eliminate HCV in high-incidence and prevalence settings. Achieving elimination by 2030 will entail concerted efforts to restore and enhance pre-pandemic levels of HCV prevention and care.

Perceptions Towards HCV Treatment with Direct Acting Antivirals (DAAs): A Qualitative Analysis with Persons with HIV/HCV Co-infection Who Delay or Refuse Treatment

In the United States, approximately 25% of people with HIV (PWH) are co-infected with hepatitis C (HCV). Since 2014, highly effective and well-tolerated direct-acting antivirals (DAAs) have revolutionized HCV treatment. Uptake of DAAs by people with HIV/HCV co-infection has improved but remains suboptimal due to system, provider, and patient-level barriers. To explore patient-level issues by better understanding their attitudes towards DAA treatment, we conducted qualitative interviews with 21 persons with HIV/HCV co-infection who did not consent to DAA treatment or delayed treatment for at least 1 year after diagnosis. We found PWH perceived DAA treatment barriers and facilitators on multiple levels of the social-ecological environment: the individual (HCV disease and treatment literacy), interpersonal (peer influence), institutional (media and healthcare provider relationship), and structural levels (treatment cost and adherence support). Recommendations to improve DAA treatment uptake include HCV-treatment adherence support, HCV disease and treatment literacy training (particularly for substance use and DAA treatment interactions), and encouraging PWH who have successfully completed DAA treatment to speak with their peers.

Barriers of linkage to HCV viremia testing among people who inject drugs in Georgia

Background

People who inject drugs (PWID) in Georgia have a high prevalence of hepatitis C virus antibody (anti-HCV). Access to care among PWID could be prioritized to meet the country’s hepatitis C elimination goals. This study assesses barriers of linkage to HCV viremia testing among PWID in Georgia.

Methods

Study participants were enrolled from 13 harm reduction (HR) centers throughout Georgia. Anti-HCV positive PWID who were tested for viremia (complete diagnosis [CD]), were compared to those not tested for viremia within 90 days of screening anti-HCV positive (not complete diagnosis [NCD]). Convenience samples of CD and NCD individuals recorded at HR centers using beneficiaries’ national ID were drawn from the National HCV Elimination Program database. Participants were interviewed about potential barriers to seeking care.

Results

A total of 500 PWID were enrolled, 245 CD and 255 NCD. CD and NCD were similar with respect to gender, age, employment status, education, knowledge of anti-HCV status, and confidence/trust in the elimination program (p > 0.05). More NCD (13.0%) than CD (7.4%) stated they were not sufficiently informed what to do after screening anti-HCV positive (p < 0.05). In multivariate analysis, HCV viremia testing was associated with perceived affordability of the elimination program (adjusted prevalence ratio = 8.53; 95% confidence interval: 4.14–17.62).

Conclusions

Post testing counselling and making hepatitis C services affordable could help increase HCV viremia testing among PWID in Georgia.

Non-Invasive Diagnosis of Liver Fibrosis in Chronic Hepatitis C using Mathematical Modeling and Simulation

Hepatitis C is a viral infection (HCV) that causes liver inflammation, and it was found that it affects over 170 million people around the world, with Egypt having the highest rate in the world. Unfortunately, serial liver biopsies, which can be invasive, expensive, risky, and inconvenient to patients, are typically used for the diagnosis of liver fibrosis progression. This study presents the development, validation, and evaluation of a prediction mathematical model for non-invasive diagnosis of liver fibrosis in chronic HCV. The proposed model in this article uses a set of nonlinear ordinary differential equations as its core and divides the population into six groups: Susceptible, Treatment, Responder, Non-Responder, Cured, and Fibrosis. The validation approach involved the implementation of two equivalent simulation models that examine the proposed process from different perspectives. A system dynamics model was developed to understand the nonlinear behavior of the diagnosis process over time. The system dynamics model was then transformed to an equivalent agent-based model to examine the system at the individual level. The numerical analysis and simulation results indicate that the earlier the HCV treatment is implemented, the larger the group of people who will become responders, and less people will develop complications such as fibrosis.

Modeling hepatitis C micro-elimination among people who inject drugs with direct-acting antivirals in metropolitan Chicago

Hepatitis C virus (HCV) infection is a leading cause of chronic liver disease and mortality worldwide. Direct-acting antiviral (DAA) therapy leads to high cure rates. However, persons who inject drugs (PWID) are at risk for reinfection after cure and may require multiple DAA treatments to reach the World Health Organization's (WHO) goal of HCV elimination by 2030. Using an agent-based model (ABM) that accounts for the complex interplay of demographic factors, risk behaviors, social networks, and geographic location for HCV transmission among PWID, we examined the combination(s) of DAA enrollment (2.5%, 5%, 7.5%, 10%), adherence (60%, 70%, 80%, 90%) and frequency of DAA treatment courses needed to achieve the WHO's goal of reducing incident chronic infections by 90% by 2030 among a large population of PWID from Chicago, IL and surrounding suburbs. We also estimated the economic DAA costs associated with each scenario. Our results indicate that a DAA treatment rate of >7.5% per year with 90% adherence results in 75% of enrolled PWID requiring only a single DAA course; however 19% would require 2 courses, 5%, 3 courses and <2%, 4 courses, with an overall DAA cost of $325 million to achieve the WHO goal in metropolitan Chicago. We estimate a 28% increase in the overall DAA cost under low adherence (70%) compared to high adherence (90%). Our modeling results have important public health implications for HCV elimination among U.S. PWID. Using a range of feasible treatment enrollment and adherence rates, we report robust findings supporting the need to address re-exposure and reinfection among PWID to reduce HCV incidence.

Gaps in hepatitis C virus prevention and care for HIV-hepatitis C virus co-infected people who inject drugs in Canada

BACKGROUND

People who inject drugs (PWID) living with HIV are a priority population for eliminating hepatitis C virus (HCV) as a public health threat. Maximizing access to HCV prevention and treatment strategies are key steps towards elimination. We aimed to evaluate engagement in harm reduction programs and HCV treatment, and to describe injection practices among HIV-HCV co-infected PWID in Canada from 2003 to 2019.

METHODS

We included Canadian Coinfection Cohort study participants who reported injecting drugs between 2003 and 2019 in Quebec, Ontario, Saskatchewan, and British Columbia, Canada. We investigated temporal trends in HCV treatment uptake, efficacy, and effectiveness; injection practices; and engagement in harm reduction programs in three time periods based on HCV treatment availability: 1) interferon/ribavirin (2003-2010); 2) first-generation direct acting antivirals (DAAs) (2011-2013); 3) second-generation DAAs (2014-2019). Harm reduction services assessed included needle and syringe programs (NSP), opioid agonist therapy (OAT), and supervised injection sites (SIS).

RESULTS

Median age of participants (N = 1,077) at cohort entry was 44 years; 69% were males. Province-specific HCV treatment rates increased among HCV RNA-positive PWID, reaching 16 to 31 per 100 person-years in 2014-2019. Treatment efficacy improved from a 50 to 70% range in 2003-2010 to >90% across provinces in 2014-2019. Drug injecting patterns among active PWID varied by province, with an overall decrease in cocaine injection frequency and increasing opioid injections. In the most recent time period (2014-2019), needle/syringe sharing was reported at 8-22% of visits. Gaps remained in engagement in harm reduction programs: NSP use decreased (58-70% of visits), OAT engagement among opioid users was low (8-26% of visits), and participants rarely used SIS (1-15% of visits).

CONCLUSION

HCV treatment uptake and outcomes have improved among HIV-HCV coinfected PWID. Yet, this population remains exposed to drug-related harms, highlighting the need to tie HCV elimination strategies with enhanced harm reduction programs to improve overall health for this population.

Qualitative behaviour of a stochastic hepatitis C epidemic model in cellular level

In this paper, a mathematical model describing the dynamical of the spread of hepatitis C virus (HCV) at a cellular level with a stochastic noise in the transmission rate is developed from the deterministic model. The unique time-global solution for any positive initial value is served. The Ito's Formula, the suitable Lyapunov function, and other stochastic analysis techniques are used to analyze the model dynamics. The numerical simulations are carried out to describe the analytical results. These results highlight the impact of the noise intensity accelerating the extinction of the disease.

Evaluating the Prevention Benefit of HCV Treatment: Modeling the SToP-C Treatment as Prevention Study in Prisons

BACKGROUND AND AIMS

Between 2014 and 2019, the SToP-C trial observed a halving in HCV incidence in four Australian prisons following scale-up of direct-acting antiviral (DAA) therapy. However, the contribution of HCV treatment to this decline is unclear because the study did not have a control group. We used modeling to consider this question.

APPROACH AND RESULTS

We parameterized and calibrated a dynamic model of HCV transmission in prisons to data from each SToP-C prison on incarceration dynamics, injecting drug use, HCV prevalence trends among prison entrants, baseline HCV incidence before treatment scale-up, and subsequent HCV treatment scale-up. The model projected the decrease in HCV incidence resulting from increases in HCV treatment and other effects. We assessed whether the model agreed better with observed reductions in HCV incidence overall and by prison if we included HCV treatment scale-up, and its prevention benefits, or did not. The model estimated how much of the observed decrease in HCV incidence was attributable to HCV treatment in prison. The model projected a decrease in HCV incidence of 48.5% (95% uncertainty interval [UI], 41.9-54.1) following treatment scale-up across the four prisons, agreeing with the observed HCV incidence decrease (47.6%; 95% CI, 23.4-64.2) from the SToP-C trial. Without any in-prison HCV treatment, the model indicated that incidence would have decreased by 7.2% (95% UI, -0.3 to 13.6). This suggests that 85.1% (95% UI, 72.6-100.6) of the observed halving in incidence was from HCV treatment scale-up, with the remainder from observed decreases in HCV prevalence among prison entrants (14.9%; 95% UI, -0.6 to 27.4).

CONCLUSIONS

Our results demonstrate the prevention benefits of scaling up HCV treatment in prison settings. Prison-based DAA scale-up should be an important component of HCV elimination strategies.

Evaluating Montréal's harm reduction interventions for people who inject drugs: protocol for observational study and cost-effectiveness analysis

INTRODUCTION

The main harm reduction interventions for people who inject drugs (PWID) are supervised injection facilities, needle and syringe programmes and opioid agonist treatment. Current evidence supporting their implementation and operation underestimates their usefulness by excluding skin, soft tissue and vascular infections (SSTVIs) and anoxic/toxicity-related brain injury from cost-effectiveness analyses (CEA). Our goal is to conduct a comprehensive CEA of harm reduction interventions in a setting with a large, dispersed, heterogeneous population of PWID, and include prevention of SSTVIs and anoxic/toxicity-related brain injury as measures of benefit in addition to HIV, hepatitis C and overdose morbidity and mortalities averted.

METHODS AND ANALYSIS

This protocol describes how we will develop an open, retrospective cohort of adult PWID living in Québec between 1 January 2009 and 31 December 2020 using administrative health record data. By complementing this data with non-linkable paramedic dispatch records, regional monthly needle and syringe dispensation counts and repeated cross-sectional biobehavioural surveys, we will estimate the hazards of occurrence and the impact of Montréal's harm reduction interventions on the incidence of drug-use-related injuries, infections and deaths. We will synthesise results from our empirical analyses with published evidence to simulate infections and injuries in a hypothetical population of PWID in Montréal under different intervention scenarios including current levels of use and scale-up, and assess the cost-effectiveness of each intervention from the public healthcare payer's perspective.

ETHICS AND DISSEMINATION

This study was approved by McGill University's Institutional Review Board (Study Number: A08-E53-19B). We will work with community partners to disseminate results to the public and scientific community via scientific conferences, a publicly accessible report, op-ed articles and open access peer-reviewed journals.

Utilising an access to care integrated framework to explore the perceptions of hepatitis C treatment of hospital-based interventions among people who use drugs

BACKGROUND

Gaps remain in the hepatitis C virus (HCV) care cascade for people who use drugs (PWUD). Acute medical or surgical illnesses requiring hospitalisation are an opportunity to address addiction, but how inpatient strategies could affect HCV care accessibility for PWUD remains unknown. We explored patient perspectives of hospital-based interventions using an integrated framework of access to HCV care.

METHODS

We conducted a qualitative study of hospitalised adults (n=27) with HCV and addiction admitted to an urban academic medical centre in the United States between June and November 2019. Individual interviews were audio-recorded, transcribed, and dual-coded. We analysed data with coding specific for hospital-based interventions including screening, conducting HCV-related laboratory work-up, starting treatment, connecting with peers, and coordinating outpatient care. We analysed coded data at the semantic level for emergent themes using a framework approach based off an integrated framework of access to HCV care.

RESULTS

The majority of participants primarily used opioids (78%), were white (85%) and men (67%). Participants frequently reported HCV screening during previous hospitalisation with rare inpatient connection to HCV-related services. Participants expressed willingness to discuss HCV treatment candidacy during hospitalisation; however, lack of inpatient conversations led to perception that "nothing could be done" during admission. Participants expressed interest in completing inpatient HCV work-up to "get the ball rollin'" - consolidating care would enhance outpatient service permeability by reducing barriers. Others resisted HCV care coordination, preferring to focus on "immediate" issues including health conditions and addiction treatment. Participants also expressed openness to engaging with peers about HCV, noting shared drug use experience as critical to a peer relationship when discussing HCV.

CONCLUSION

Hospitalised PWUD have varied priorities, necessitating adaptable interventions for addressing HCV. Hospitalisation can be an opportunity to address HCV access to care including identification of treatment eligibility, consolidation of care, and facilitation of HCV-related referrals.

Quantifying transmission dynamics of acute hepatitis C virus infections in a heterogeneous population using sequence data

Opioid substitution and syringes exchange programs have drastically reduced hepatitis C virus (HCV) spread in France but HCV sexual transmission in men having sex with men (MSM) has recently arisen as a significant public health concern. The fact that the virus is transmitting in a heterogeneous population, with different transmission routes, makes prevalence and incidence rates poorly informative. However, additional insights can be gained by analyzing virus phylogenies inferred from dated genetic sequence data. By combining a phylodynamics approach based on Approximate Bayesian Computation (ABC) and an original transmission model, we estimate key epidemiological parameters of an ongoing HCV epidemic among MSMs in Lyon (France). We show that this new epidemic is largely independent of the previously observed non-MSM HCV epidemics and that its doubling time is ten times lower (0.44 years versus 4.37 years). These results have practical implications for HCV control and illustrate the additional information provided by virus genomics in public health.

On fractional approaches to the dynamics of a SARS-CoV-2 infection model including singular and non-singular kernels

Covid-19 (2019-nCoV) disease has been spreading in China since late 2019 and has spread to various countries around the world. With the spread of the disease around the world, much attention has been paid to epidemiological knowledge. This knowledge plays a key role in understanding the pattern of disease transmission and how to prevent a larger population from contracting it. In the meantime, one should not overlook the significant role that mathematical descriptions play in epidemiology. In this paper, using some known definitions of fractional derivatives, which is a relatively new definition in differential calculus, and then by employing them in a mathematical framework, the effects of these tools in a better description of the epidemic of a SARS-CoV-2 infection is investigated. To solve these problems, efficient numerical methods have been used which can provide a very good approximation of the solution of the problem. In addition, numerical simulations related to each method will be provided in solving these models. The results obtained in each case indicate that the used approximate methods have been able to provide a good description of the problem situation.

Injecting network structure determines the most efficient strategy to achieve Hepatitis C elimination in people who inject drugs

Transmission of Hepatitis C (HCV) continues via sharing of injection equipment between people who inject drugs (PWID). Network-based modelling studies have produced conflicting results about whether random treatment is preferable to targeting treatment at PWID with multiple partners. We hypothesise that differences in the modelled injecting network structure produce this heterogeneity. The study aimed to test how changing network structure affects HCV transmission and treatment effects. We created three dynamic injecting network structures connecting 689 PWID (UK-net, AUS-net and USA-net) based on published empirical data. We modelled HCV in the networks and at 5 years compared prevalence of HCV 1) with no treatment, 2) with randomly targeted treatment and 3) with treatment targeted at PWID with the most injecting partnerships (degree-based treatment). HCV prevalence at 5 years without treatment differed significantly between the three networks (UK-net (42.8%) vs. AUS-net (38.2%), p < 0.0001 and vs. USA-net (54.0%), p < 0.0001). In the treatment scenarios UK-net and AUS-net showed a benefit of degree-based treatment with a 5-year prevalence of 1.0% vs. 9.6% p < 0.0001 and 0.15% vs. 0.44%, p < 0.0001. USA-net showed no significant difference (29.3% vs. 29.2%, p = 0.0681). Degree-based treatment was optimised with low prevalence, moderate treatment coverage conditions whereas random treatment was optimised in low treatment coverage, high prevalence conditions. In conclusion, injecting network structure determines the transmission rate of HCV and the most efficient treatment strategy. In real-world injecting network structures, the benefit of targeting HCV treatment at individuals with multiple injecting partnerships may have been underestimated.

Progress on the elimination of viral hepatitis in Zimbabwe: A review of the policies, strategies and challenges

Very few low-income countries have developed national plans to achieve the viral hepatitis elimination targets set in the World Health Organization (WHO) strategy. We reviewed the policy environment, strategies and challenges on the fight against viral hepatitis in Zimbabwe. The review focussed on the Ministry of Health and Child Care (MoHCC) policy documents, strategic plans and reports. We performed key informant interviews to enhance evidence generated from the document review. Twelve documents were reviewed and interviews with 10 key informants were completed. The MoHCC established a technical working group to work towards elimination of viral hepatitis. The technical working group drafted a strategic plan for elimination of viral hepatitis; however, it is still awaiting implementation. Key strategies that are working well include screening of donated blood for transfusion, safe injection practices and hepatitis B virus (HBV) three-dose vaccination. Current challenges in the drive towards elimination of viral hepatitis include poor to non-existent surveillance systems, lack of epidemiological data, absence of the HBV vaccine birth dose and lack of systematic screening and treatment services for viral hepatitis. In conclusion, despite political will demonstrated towards achieving viral hepatitis elimination, substantial investment and work are required to implement the strategic plan and realize significant success.

Exploring how hospitalization can alter hepatitis c virus treatment prioritization and trajectories in people who use drugs: A qualitative analysis

Background: People who use drugs (PWUD) have high rates of hepatitis C virus (HCV) infection. Hospitalization can be a time for PWUD to engage in addiction treatment, but little is known about how hospitalization shapes HCV treatment readiness. We aimed to describe how hospitalization and addiction medicine consult service (AMCS) can alter HCV prioritization of inpatient PWUD with HCV. Methods: We conducted a qualitative study consisting of semi-structured interviews (n = 27) of hospitalized adults with addiction and HCV infection seen by an AMCS at a single, urban, academic center. Interviews were audio-recorded, transcribed, and coded iteratively at the semantic level, and analyzed for themes. Results: Of the 27 participants, most identified as Caucasian (85%), male gender (67%), and they primarily used opioids (78%); approximately half (48%) reported HCV diagnosis over 5 years ago. We identified three main themes around hospitalization altering the prioritizations and HCV treatment preferences for PWUD: (1) HCV treatment non-engaged (2) HCV treatment urgency, and (3) HCV treatment in the future. Those wanting to treat HCV-whether urgently or in the future-shared the overlapping theme of hospitalization as a reachable moment for their addiction and HCV. These participants recognized the long-term benefits of addressing HCV and connected their hospitalization to substance use. Conclusion: In our study, PWUD with HCV expressed varying and competing priorities and life circumstances contributing to three main HCV treatment trajectories. Our results suggest ways hospitalization can serve as an HCV touchpoint for PWUD, especially in the context of addressing substance use, and could be used when designing and implementing targeted interventions to improve the HCV care continuum for PWUD.

Hepatitis C Virus Transmission Clusters in Public Health and Correctional Settings, Wisconsin, USA, 2016-20171

Ending the hepatitis C virus (HCV) epidemic requires stopping transmission among networks of persons who inject drugs. Identifying transmission networks by using genomic epidemiology may inform community responses that can quickly interrupt transmission. We retrospectively identified HCV RNA–positive specimens corresponding to 459 persons in settings that use the state laboratory, including correctional facilities and syringe services programs, in Wisconsin, USA, during 2016–2017. We conducted next-generation sequencing of HCV and analyzed it for phylogenetic linkage by using the Centers for Disease Control and Prevention Global Hepatitis Outbreak Surveillance Technology platform. Analysis showed that 126 persons were linked across 42 clusters. Phylogenetic clustering was higher in rural communities and associated with female sex and younger age among rural residents. These data highlight that HCV transmission could be reduced by expanding molecular-based surveillance strategies to rural communities affected by the opioid crisis.

State estimation-based control of COVID-19 epidemic before and after vaccine development

In this study, a nonlinear robust control policy is designed together with a state observer in order to manage the novel coronavirus disease (COVID-19) outbreak having an uncertain epidemiological model with unmeasurable variables. This nonlinear model for the COVID-19 epidemic includes eight state variables (susceptible, exposed, infected, quarantined, hospitalized, recovered, deceased, and insusceptible populations). Two plausible scenarios are put forward in this article to control this epidemic before and after its vaccine invention. In the first scenario, the social distancing and hospitalization rates are employed as two applicable control inputs to diminish the exposed and infected groups. However, in the second scenario after the vaccine development, the vaccination rate is taken into account as the third control input to reduce the susceptible populations, in addition to the two objectives of the first scenario. The proposed feedback control measures are defined in terms of the hospitalized and deceased populations due to the available statistical data, while other unmeasurable compartmental variables are estimated by an extended Kalman filter (EKF). In other words, the susceptible, exposed, infected, quarantined, recovered, and insusceptible individuals cannot be identified precisely because of the asymptomatic infection of COVID-19 in some cases, its incubation period, and the lack of an adequate community screening. Utilizing the Lyapunov theorem, the stability and bounded tracking convergence of the closed-loop epidemiological system are investigated in the presence of modeling uncertainties. Finally, a comprehensive simulation study is conducted based on Canada's reported cases for two defined timing plans (with different treatment rates). Obtained results demonstrate that the developed EKF-based control scheme can achieve desired epidemic goals (exponential decrease of infected, exposed, and susceptible people).

Excitable models: Projections, targets, and the making of futures without disease

In efforts to control disease, mathematical models and numerical targets play a key role. We take the elimination of a viral infection as a case for exploring mathematical models as 'evidence-making interventions'. Using interviews with mathematical modellers and implementation scientists, and focusing on the emergence of models of 'treatment-as-prevention' in hepatitis C control, we trace how projections detach from their calculative origins as social and policy practices. Drawing on the work of Michel Callon and others, we show that modelled projections of viral elimination circulate as 'qualculations', taking flight via their affects, including as anticipation. Modelled numerical targets do not need 'actual numbers' or precise measurements to perform their authority as evidence of viral elimination or as situated matters-of-concern. Modellers grapple with the ways that their models transform in policy and social practices, apparently beyond reasonable calculus. We highlight how practices of 'holding-on' to projections in relation to imaginaries of 'evidence-based' science entangle with the 'letting-go' of models beyond calculus. We conclude that the 'virtual precision' of models affords them fluid evidence-making potential. We imagine a different mode of modelling science in health, one more attuned to treating projections as qualculative, affective and relational, as excitable matter.

Concurrent Initiation of Hepatitis C and Opioid Use Disorder Treatment in People Who Inject Drugs

BACKGROUND

People who inject drugs have a high prevalence of hepatitis C virus (HCV) and significant disease associated with drug use; however, HCV treatment often occurs in absence of interventions to address opioid use disorder and drug use-related harms. The impact of concurrent initiation of opioid agonist therapy (OAT) on HCV treatment and drug use outcomes is unknown.

METHODS

In this prospective, open-label, observational trial at a harm reduction organization's drop-in center in Washington, DC, 100 patients with chronic HCV infection, opioid use disorder, and ongoing injection drug use were treated with sofosbuvir-velpatasvir for 12-weeks and offered buprenorphine initiation. The primary end point was sustained virologic response (SVR), and secondary end points included uptake of and retention in OAT, change in risk behavior, and determinants of SVR.

RESULTS

Eighty-two patients (82%) achieved SVR, which was not associated with baseline OAT status (P = .33), on-treatment drug use (P >.99), or imperfect daily adherence (P = .35) but was significantly associated with completing 2 or more 28-pill bottles of sofosbuvir-velpatasvir (P < .001) and receiving OAT at week 24 (P = .01). Of 67 patients not already receiving OAT at baseline, 53 (79%) started OAT. At week 24, 68 (68%) patients were receiving OAT. Receipt of OAT was associated with fewer opiate-positive urine drug screens (P = .003), lower human immunodeficiency virus risk-taking behavior scores (P < .001), and lower rates of opioid overdose (P = .04).

CONCLUSIONS

The Novel Model of Hepatitis C Treatment as an Anchor to Prevent HIV, Initiate Opioid Agonist Therapy, and Reduce Risky Behavior study demonstrates high uptake of buprenorphine collocated with HCV treatment, and it shows that concurrent initiation of OAT with HCV treatment can result in high rates of SVR while reducing risks associated with drug use.

CLINICAL TRIALS REGISTRATION

NCT03221309.

Development of an Interdisciplinary Telehealth Model of Provider Training and Comprehensive Care for Hepatitis C and Opioid Use Disorder in a High-Burden Region

BACKGROUND

Hepatitis C virus (HCV) and the opioid epidemic disproportionately affect the Appalachian region. Geographic and financial barriers prevent access to specialty care. Interventions are needed to address the HCV-opioid syndemic in this region.

METHODS

We developed an innovative, collaborative telehealth model in Southwest Virginia featuring bidirectional referrals from and to comprehensive harm reduction (CHR) programs and office-based opioid therapy (OBOT), as well as workforce development through local provider training in HCV management. We aimed to (1) describe the implementation process of provider training and (2) assess the effectiveness of the telehealth model by monitoring patient outcomes in the first year.

RESULTS

The provider training model moved from a graduated autonomy model with direct specialist supervision to a 1-day workshop with parallel tracks for providers and support staff followed by monthly case conferences. Forty-four providers and support staff attended training. Eight providers have begun treating independently. For the telehealth component, 123 people were referred, with 62% referred from partner OBOT or CHR sites; 103 (84%) attended a visit, 93 (76%) completed the treatment course, and 61 (50%) have achieved sustained virologic response. Rates of sustained virologic response did not differ by receipt of treatment for opioid use disorder.

CONCLUSIONS

Providers demonstrated a preference for an in-person training workshop, though further investigation is needed to determine why only a minority of those trained have begun treating HCV independently. The interdisciplinary nature of this program led to efficient treatment of hepatitis C in a real-world population with a majority of patients referred from OBOTs and CHR programs.

Combined treatment and prevention strategies for hepatitis C virus elimination in the prisons in New South Wales: a modelling study

BACKGROUND AND AIMS

Australia is currently on track to meet the World Health Organization (WHO) global hepatitis C virus (HCV) elimination goals by 2030, reflecting universal subsidized access to testing and direct-acting antiviral (DAA) treatment. In New South Wales, DAA treatment in prisons has scaled-up substantially, with 1000 prisoners treated in 2017. However, HCV prevalence and incidence in this setting is high, which could undermine elimination efforts. This study aimed to test the preventative effects of DAA treatment scale-up, opiate substitution treatment (OST) and needle and syringe programme (NSP) strategies for prisons.

DESIGN

Modelling study using an individual-based mathematical model of a typical prison setting. The model was calibrated against Australian epidemiological data sets and executed in-prison events for each individual daily, including movements between prisons, changes in risk behaviour and uptake of prevention measures such as OST and NSP, as well as DAA treatment. Scenarios were projected from 2018 to 2030.

SETTING

New South Wales prisons.

PARTICIPANTS

New South Wales prisoners.

MEASUREMENTS

Variables including prison populations, prevalence and incidence rate were calculated. Prisoners were described by demographic characteristics, HCV infection history, risk behaviours and accessing treatment and prevention measures in varied security settings.

FINDINGS

Increasing the number of prisoners treated for HCV to 2000 annually was projected to reduce the HCV incidence rate to 8.69 [95% confidence interval (CI) = 8.17, 9.20] per 100 person-years (100 p.y.). Combined treatment and prevention strategies were necessary to reduce the projected incidence rate to 5.22 (95% CI = 5.13, 5.52) per 100 p.y. Considering the expected reductions in the prevalence of chronic HCV in the Australian community, incidence rate was predicted to drop to 0.93 (95% CI = 0.92, 0.98) per 100 p.y. by 2030.

CONCLUSIONS

This model, which simulates prison scenarios to inform Australia's national hepatitis C virus elimination efforts, suggests that continued direct-acting antiviral (coverage in the community combined with a moderate increase of direct-acting antiviral treatments in prisons, and introduction of improved harm reduction via opiate substitution treatment and/or needle and syringe programmes, makes hepatitis C virus elimination feasible in Australian prisons.

Dynamic modeling of hepatitis C transmission among people who inject drugs

To reach the WHO goal of hepatitis C elimination, it is essential to identify the number of people unaware of their hepatitis C virus (HCV) infection and to investigate the effect of interventions on the disease transmission dynamics. In many high-income countries, one of the primary routes of HCV transmission is via contaminated needles shared by people who inject drugs (PWIDs). However, substantial underreporting combined with high uncertainty regarding the size of this difficult to reach population, makes it challenging to estimate the core indicators recommended by the WHO. To support progress toward the elimination goal, we present a novel multi-layered dynamic transmission model for HCV transmission within a PWID population. The model explicitly accounts for disease stage (acute and chronic), injection drug use status (active and former PWIDs), status of diagnosis (diagnosed and undiagnosed) and country of disease acquisition (domestic or abroad). First, based on this model, and using routine surveillance data, we estimate the number of undiagnosed PWIDs, the true incidence, the average time until diagnosis, the reproduction numbers and associated uncertainties. Second, we examine the impact of two interventions on disease dynamics: (1) direct-acting antiviral drug treatment, and (2) needle exchange programs. As a proof of concept, we illustrate our results for a specific data set. In addition, we develop a web application to allow our model to be explored interactively and with different parameter values.

Hepatitis C virus modelled as an indirectly transmitted infection highlights the centrality of injection drug equipment in disease dynamics

The hepatitis C virus (HCV) epidemic often occurs through the persistence of injection drug use. Mathematical models have been useful in understanding various aspects of the HCV epidemic, and especially, the importance of new treatment measures. Until now, however, few models have attempted to understand HCV in terms of an interaction between the various actors in an HCV outbreak-hosts, viruses and the needle injection equipment. In this study, we apply perspectives from the ecology of infectious diseases to model the transmission of HCV among a population of injection drug users. The products of our model suggest that modelling HCV as an indirectly transmitted infection-where the injection equipment serves as an environmental reservoir for infection-facilitates a more nuanced understanding of disease dynamics, by animating the underappreciated actors and interactions that frame disease. This lens may allow us to understand how certain public health interventions (e.g. needle exchange programmes) influence HCV epidemics. Lastly, we argue that this model is of particular importance in the light of the modern opioid epidemic, which has already been associated with outbreaks of viral diseases.

Characterising the policy influence of peer-based drug user organisations in the context of hepatitis C elimination

BACKGROUND

Achieving hepatitis C (HCV) elimination goals will require major policy and health service reorientation to scale up testing and treatment among people who inject drugs (PWID). To achieve this, a close partnership with peer-based drug user organisations is required. However, peer organisations have historical and ongoing difficulties in articulating the validity of their service delivery and policy advice, leading to some policy and health services resisting partnership and advice from peer-based drug user organisations.

METHODS

To develop a deeper understanding of the role of peer-based drug user organisations in the HCV response, we analysed data from the W3 Project which used systems thinking methods to draw together the insights of over 90 peer staff from 10 Australian community and peer organisations in HCV and HIV. The resulting system maps were analysed to identify system dynamics and functions that need to be fulfilled for peer organisations to be influential within their community and policy system.

RESULTS

We identified the interactions at a system level which can enhance or constrain the quality and influence of policy advice from peer-based drug user organisations. We found the strength of Peer-based drug user organisations to support the scale up of HCV testing and treatment was their capacity to mediate between, and navigate within, the complex community and policy/health service systems. While peer-based drug user organisations endeavour to demonstrate their capacity and credibility in terms of engagement, alignment, adaptation and influence, policy and service organisations also need recognise their own system role to value and enable peer-based drug user organisations to achieve their potential.

CONCLUSION

If the HCV prevention and treatment system is to reach PWID living with HCV and achieve HCV elimination goals, then policy and health services need to invest in strengthening peer-based drug user organisations as well as recognise, value and act on quality policy advice from PWID peer leadership.

Conceptualising access in the direct-acting antiviral era: An integrated framework to inform research and practice in HCV care for people who inject drugs

As direct-acting antiviral (DAA) therapy costs fall and eligibility criteria are relaxed, people who inject drugs (PWID) will increasingly become eligible for HCV treatment. Yet eligibility does not necessarily equate to access. Amidst efforts to expand treatment uptake in this population, we seek to synthesise and clarify the conceptual underpinnings of access to health care for PWID, with a view to informing research and practice. Integrating dominant frameworks of health service utilisation, care seeking processes, and ecological perspectives on health promotion, we present a comprehensive theoretical framework to understand, investigate and intervene upon barriers and facilitators to HCV care for PWID. Built upon the concept of Candidacy, the framework describes access to care as a continually negotiated product of the alignment between individuals, health professionals, and health systems. Individuals must identify themselves as candidates for services and then work to stake this claim; health professionals serve as gatekeepers, adjudicating asserted candidacies within the context of localised operating conditions; and repeated interactions build experiential knowledge and patient-practitioner relationships, influencing identification and assertion of candidacy over time. These processes occur within a complex social ecology of interdependent individual, service, system, and policy factors, on which other established theories provide guidance. There is a pressing need for a deliberate and nuanced theory of health care access to complement efforts to document the HCV 'cascade of care' among PWID. We offer this framework as an organising device for observational research, intervention, and implementation science to expand access to HCV care in this vulnerable population. Using practical examples from the HCV literature, we demonstrate its utility for specifying research questions and intervention targets across multiple levels of influence; describing and testing plausible effect mechanisms; and identifying potential threats to validity or barriers to research translation.