Evidence for a substantial role of sharing of injecting paraphernalia other than syringes/needles to the spread of hepatitis C among injecting drug users

Hepatitis C: clinical and biological features related to different forms of cocaine use

INTRODUCTION

Hepatitis C virus (HCV) infection is related with several liver diseases such as cirrhosis and hepatocellular carcinomas, leading to more than 0.5 million deaths every year and to a great global burden. It is known that injection drug users show a high prevalence of HCV infection, being considered a risk group for this disease. Cocaine users seem to be in greater risk than other drug users, and several hypotheses for this association are being studied.

AIM

To review data on HCV infection in cocaine users, taking into consideration the relevance of the different routes of drug administration and other risk behaviors.

METHODS

This was a narrative review performed in the main scientific databases.

RESULTS AND CONCLUSION

Data suggest that cocaine use could be associated with HCV infection due to the specificities of cocaine consumption pattern, even in those subjects who do not inject drugs, in addition to other risky behaviors, such as tattooing and unprotected sex. Injectable cocaine users seem to be more susceptible to contamination than users who do not inject drugs. However, evidence is pointing to the possibility of infection by sharing drug paraphernalia other than syringes. Moreover, specific immune system impairments caused by cocaine use are also being linked with HCV infection susceptibility, persistence and increased pathological effects.

Effectiveness and cost-effectiveness of interventions targeting harm reduction and chronic hepatitis C cascade of care in people who inject drugs: The case of France

Direct-acting antivirals (DAAs) represent an opportunity to improve hepatitis C virus (HCV) care cascade. This combined with improved harm reduction interventions may lead to HCV elimination especially in people who inject drugs (PWID). We assessed the effectiveness/cost-effectiveness of improvements in harm reduction and chronic hepatitis C (CHC) care cascade in PWID in France. We used a dynamic model of HCV transmission and CHC natural history and evaluated the following: improved needle/syringe programmes-opioid substitution therapies, faster diagnosis/linkage to care, earlier treatment initiation, alone and in combination among active PWID (mean age = 36). Outcomes were as follows: life expectancy in discounted quality-adjusted life years (QALYs); direct lifetime discounted costs; incremental cost-effectiveness ratio (ICER); number of infections/reinfections. Under the current practice, life expectancy was 15.846 QALYs, for a mean lifetime cost of €20 762. Treatment initiation at F0 fibrosis stage alone was less effective and more costly than faster diagnosis/linkage to care combined with treatment initiation at F0, which increased life expectancy to 16.694 QALYs, decreased new infections by 37%, with a ICER = €5300/QALY. Combining these interventions with harm reduction improvements was the most effective scenario (life expectancy = 16.701 QALYs, 41% decrease in new infections) but was not cost-effective (ICER = €105 600/QALY); it became cost-effective with higher initial HCV incidence rates and lower harm reduction coverage than in our base-case scenario. This study illustrated the high effectiveness, and cost-effectiveness, of a faster diagnosis/linkage to care together with treatment from F0 with DAAs. This "Test and treat" strategy should play a central role both in improving the life expectancies of HCV-infected patients, and in reducing HCV transmission.

Prevalence of hepatitis C virus in young people who inject drugs in four Colombian cities: A cross-sectional study using Respondent Driven Sampling

BACKGROUND

Colombia has a growing population of young people who inject drugs (PWID). Despite the previously reported association of injection drug use with hepatitis c virus (HCV) in other countries, studies on HCV prevalence in PWID in Colombia are lacking. The objective of this study is to determine the prevalence, demographics, and correlations of risky injection behaviours in HCV seropositive PWID in four Colombian cities (Armenia, Bogotá, Cúcuta and Pereira).

METHODS

This was a cross-sectional study carried out between January and June of 2014 that included 918 PWID from four Colombian cities, recruited by Respondent Driven Sampling. A survey was administered to each participant, and blood samples were collected. Binary logistic regression and multivariate analyses for each city were conducted.

RESULTS

Average participant age was 26 years (SD 6.5). Of all participants, 27.3% of PWID were HCV seropositive, of which 52% were 25 years old or younger. In Pereira, increased risk of HCV infection was found for PWID that: had a history of injection drug use of 5 years or more (AOR: 3.0, CI: 1.7-7.8); were between 25 and 28 years of age (AOR: 5.2, CI: 1.0-26.3); had higher injection frequency (AOR: 2.5, CI: 1.4-4.2), and daily use of gifted, sold, or rented needles or syringes (AOR: 4.5, CI: 1.0-7.1). Additionally, in Cucuta, being HIV seropositive appeared to be greatly associated with risk of HCV seropositivity (AOR: 16.9, CI: 3.5-81.5).

CONCLUSION

Although prevalence of HCV in PWID in Colombia is lower than that reported for other countries, the described demographic characteristics and diverse risky injection behaviors on each city, in the context of a young PWID population with a short injection drug use history, should be taken into account in order to guide efforts towards preventing and reducing risk of HCV infection in PWID in Colombia.

A Descriptive Examination of Nonmedical Fentanyl Use in the United States: Characteristics of Use, Motives, and Consequences

Little is currently known about nonmedical fentanyl use (NFU; that is, use of illicit or pharmaceutically produced fentanyl without a prescription or in ways other than prescribed) despite increases in prevalence and consequences (e.g., overdose, fatality). Individuals with a lifetime history of NFU ( N = 122) in the United States completed an online survey assessing demographics and factors related to use. Results revealed diversion of prescriptions, unintentional use of illicit fentanyl, and high co-occurrence of mental illness and other illicit substance use among users. Commonly reported motives reflected negative/positive reinforcement (e.g., to relieve stress, to get high) and relieving pain/physical discomfort, regardless of frequency of use. More severe consequences (e.g., increased tolerance, withdrawal) were reported among high frequency users. This descriptive examination of NFU may aid in the identification of individuals at-risk for use, promote an understanding of reasons for use, and guide prevention and intervention developments.

Clinical Characteristics and Treatment Efficasy of Chronic HCV Infection Among Intravenous Drug Users in Tuzla Canton

Introduction:

Chronic HCV infection is chronic inflamatory liver disease caused by hepatitis C virus. Anti HCV prevalence among intravenous drug users (IVDU) is very high and it accounts 40% -90% (60%-90%) with the risk of 80% of developing the chronic infection.

Aim:

The aims of this study were: a) to compare clinical characteristics of chronic HCV infection among IVDU and non-users population and to detect their impact to treatment outcome; b) to investigate the treatment efficacy comparing sustained viral response (SVR) in these two populations in Tuzla Canton.

Patients and methods:

The study was retrospective-prospective and included 45 IVDU of both sexes from Tuzla Canton which were treated from chronic HCV infection with Pegilated interferon 2a/2b + ribavirin in the Clinic for Infectious Diseases and Clinic for Internal Disease of University Clinical Centre in Tuzla. The control group were presented by non-users who completed therapy in both Clinics. For statistical analyses it was used statistical package SPSS 20,0 (SPSS Inc, Chicago, IL, USA) with tests of descriptive statistics with measures of central tendency and dispersion. Quantitative variables were tested by t-test or by Mann-Whitney test. Qualitative variables were tested by hi-square test or by Fisher’s test. The standard analyse of level’s risk was used too. The analyse of predictive value of EVR for achieving the ETR and SVR was done by cross-tabulation. The impact of known factors for achieving the SVR was evaluated by logistic regression analyses. All tests were done with statistical level of significance of 95% (p=0,05).

Results:

Men were more dominant in the test group (93,3% / 61,7%), also younger age (p<0,001) and lower BMI (p=0,019). The test group had significant higher basal values of Le, Hb, Plt and ALT and tendency to lower stages of fibrosis (p=0,08). The difference in genotype frequencies was statistically significant (p=0,001) with clearly dominance of G3 and G4 among IVDU. Treatment was not complited by two patients in both groups (4,4% /3,3%). EVR was significantly higher in test group (p=0,001) so did the ETR (p=0,002) and SVR (p<0,001). Predictive factors for SVR were: age (negative predictive factor), male sex, absence of reduction of pegilated interferon and ribavirin, Metavir stage of fibrosis and presence of EVR.

Conclusion:

Population of IVDU were adherent to treatment protocol and with excellent treatment response they justified the hope of health care workers for success treatment of this population.

Hepatitis C infection and other drug-related harms among inpatients who injected drugs in Turkey

Hepatitis C virus (HCV) is easily spread among those who share drug injection equipment. Due to the ease of contraction and growing prevalence of HCV in Eastern Europe, the aims of this study focused on describing risky injection practices as well as the prevalence of HCV, HIV and hepatitis B virus (HBV) among people who inject drugs (PWID) who were admitted to public and private drug treatment centres in Turkey from 2012 to 2013. Other aims included identifying correlates of needle sharing and HCV infection. Of the 4694 inpatients who ever injected drugs and the 3914 who injected in the past 30 days, nearly all (98%) reported heroin as their drug of choice, the vast majority reported ever sharing a needle (73.4% and 79.3%), and the mean age at first injection was 23 years. Of current PWID, 51.9% were HCV-positive, 5.9% were HBV-positive and only 0.34% of lifetime PWID were HIV-positive. Predictors of increased needle sharing include younger age, being unemployed, having lesser education and reporting heroin as a drug of choice. Significant predictors of HCV infection included being 40 years or older, receiving treatment in the Mediterranean region of Turkey, reporting heroin as a primary substance, a longer duration of drug use and sharing needles. With this information, it is essential to improve access to clean injection equipment in Turkey, to focus on improving education on clean injection practices and to enhance efforts in testing and treating HCV-positive PWID.

HCV/HIV coinfection among people who inject drugs and enter opioid substitution treatment in Greece: prevalence and correlates

Background

HCV/HIV coinfection in people who inject drugs is a public health issue, which presents a variety of challenges to healthcare providers. The determinants of HCV/HIV coinfection in this population are nonetheless not well known. The aim of the present study is to identify the factors associated with HCV/HIV coinfection in people who inject drugs and enter drug-related treatment.

Methods

Linked serological and behavioral data were collected from people who entered 38 opioid substitution treatment clinics in central and southern Greece between January and December 2013. Three mutually exclusive groups were defined based on the presence of HCV and HIV antibodies. Group 1 clients had neither infection, Group 2 had HCV but not HIV, and Group 3 had HCV/HIV coinfection. Multinomial logistic regression analyses identified differences between groups according to socio-demographic, drug use and higher-risk behavioral characteristics.

Results

Our study population consisted of 580 people who injected drugs in the past 12 months (79.8 % males, with median age 36 years).79.4 % were HCV and 15.7 % HIV infected. Of those with complete serological data in both HCV and HIV indicators, 20.4 % were uninfected, 64.0 % HCV monoinfected, and 14.9 % HCV/HIV coinfected. HCV infection with or without HIV coinfection was positively associated with living alone or with a spouse/partner without children, prior incarceration, drug injecting histories of ≥10 years, and syringe sharing in the past 12 months, and negatively associated with never having previously been tested for HCV. HCV/HIV coinfection, but not HCV infection alone, was positively associated with residence in urban areas (relative risk ratio [RRR] = 4.8, 95 % confidence interval [CI]: 1.7–13.7, p = 0.004) and averaging >3 injections a day in the past 30 days (RRR = 4.5, 95 % CI: 1.6–12.8, p = 0.005), and negatively associated with using a condom in the last sexual intercourse.

Conclusions

People who inject drugs and live in urban areas and inject frequently have higher risk of coinfection. Findings highlight the need for scaling-up needle and syringe programs in inner city areas and promoting access of this population to screening and treatment, especially in prisons. The protective role of living with parents and children could inform the implementation of indicated interventions.

Factors associated with needle sharing among people who inject drugs in Yunnan, China: a combined network and regression analysis

Background

Network analyses have been widely utilized to evaluate large datasets, but have not yet been used to explore factors associated with risk behaviours. In combination with traditional regression analysis, network analyses may provide useful information and highlight key factors for reducing needle sharing behaviours among people who inject drugs (PWID).

Methods

Sociodemographic data, and information on injection behaviour and sexual practices were collected from a cross-sectional survey that was conducted with PWID in five prefectures of Yunnan province, China. A combination of logistic regression and correlation network analyses were used to explore key factors for reducing needle-sharing behaviours among PWID.

Results

In a total of 1 049 PWID, 37.5 % had a history of needle or syringe sharing. The logistic analysis showed that Zhaotong, Qujing, Dehong, or Lincang residents, diazepam use, longer injection duration, needle reuse, and infection with HIV, viral hepatitis, tuberculosis and/or malaria were independently associated with needle sharing. The correlation network analyses showed that, compared to PWID who had never shared needles, PWID who did share needles would achieve harm reduction goals faster and more permanently. HIV serostatus and marital status were found to be closely associated with other risk factors. By combining regression analyses with network analyses, it was shown that PWID who are HIV seropositive will be an ideal target group for harm reduction programs.

Conclusion

Needle-sharing behaviours are common among PWID in Yunnan, and harm reduction programs may help PWID who are HIV seropositive reduce risk behaviours and prevent blood borne diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-016-0169-y) contains supplementary material, which is available to authorized users.

Hepatitis C treatment as prevention of viral transmission and liver-related morbidity in persons who inject drugs

Hepatitis C virus (HCV) seroprevalence remains high in people who inject drug (PWID) populations, often above 60%. Highly effective direct-acting antiviral (DAA) regimens (90% efficacy) are becoming available for HCV treatment. This therapeutic revolution raises the possibility of eliminating HCV from this population. However, for this, an effective cascade of care is required. In the context of the available DAA therapies, we used a dynamic individual-based model including a model of the PWID social network to simulate the impact of improved testing, linkage to care, and adherence to treatment, and of modified treatment recommendation on the transmission and on the morbidity of HCV in PWID in France. Under the current incidence and cascade of care, with treatment initiated at fibrosis stage ≥F2, HCV prevalence decreased from 42.8% to 24.9% (95% confidence interval: 24.8-24.9) after 10 years. Changing treatment initiation criteria to treat from F0 was the only intervention leading to a substantial additional decrease in prevalence, which fell to 11.6% (95% CI: 11.6-11.7) at 10 years. Combining this change with improved testing, linkage to care, and adherence to treatment decreased HCV prevalence to 7.0% (95% CI: 7.0-7.1) at 10 years and avoided 15% (95% CI: 14-17) and 29% (95% CI: 28-30) of cirrhosis complications over 10 and 40 years, respectively.

CONCLUSIONS

Major decreases in prevalent HCV infections occur only when treatment is initiated at early stages of fibrosis, suggesting that systematic treatment in PWID, where incidence remains high, would be beneficial. However, elimination within the 10 next years will be difficult to achieve using treatment alone, even with a highly improved cascade of care.

Hepatitis C virus and HIV seroprevalences, sociodemographic characteristics, behaviors and access to syringes among drug users, a comparison of geographical areas in France, ANRS-Coquelicot 2011 survey

BACKGROUND

People who use drugs (PWUDs) are at a high risk for hepatitis C virus (HCV) and human immunodeficiency virus (HIV), but they have different characteristics depending on the local context. In France, seroprevalence, sociodemographic, and behavior information have only been studied at a national level rather than at a local level. The aim of this study was to describe and examine profile and drug use practice differences in seven French cities and departments and to assess whether these differences can explain HCV and HIV seroprevalence variations between French geographical areas.

METHODS

Data were collected from the cross-sectional ANRS-Coquelicot survey conducted for the second time in 2011 among drug users having injected or snorted drugs at least once in their life. Professional interviewers administrated a face-to-face questionnaire in six different areas in France: Paris, Marseille, Bordeaux, Lille, Strasbourg and the Seine-Saint-Denis department (Paris suburbs). Participants were asked to self-collect a fingerpick blood sample in order to search for the presence of anti-HIV and anti-HCV antibodies and to estimate seroprevalence in PWUDs.

RESULTS

Overall, HCV and HIV seroprevalence was 44% [95% CI: 39.6-47.9] and 10% [95% CI: 7.5-12.6] respectively. The highest HCV seroprevalence was 56% in Marseille and the lowest was 24% in Bordeaux and for HIV the highest was 18% in Seine-Saint-Denis and the lowest was 0% in Lille. The population's age differed between areas and could mostly explain HCV seroprevalence variation but not exclusively. Profiles and practices, different in each area, can also explain this variation. In multivariate analysis, HCV seroprevalence was lower in Bordeaux (prevalence ratio [PR]=0.64), Strasbourg (PR=0.76), and Seine-Saint-Denis (PR=0.8) than in Paris. Nearly one-third of injectors declared having had difficulties to obtain syringes in the 6 previous months, but disparities existed between areas.

CONCLUSION

HCV risk exposure in PWUDs remains high in France and varies between different areas. Innovative harm reduction strategies including educative programs about safe injecting and supervised consumption rooms need to be developed.

Dynamic modelling of hepatitis C virus transmission among people who inject drugs: a methodological review

Equipment sharing among people who inject drugs (PWID) is a key risk factor in infection by hepatitis C virus (HCV). Both the effectiveness and cost-effectiveness of interventions aimed at reducing HCV transmission in this population (such as opioid substitution therapy, needle exchange programmes or improved treatment) are difficult to evaluate using field surveys. Ethical issues and complicated access to the PWID population make it difficult to gather epidemiological data. In this context, mathematical modelling of HCV transmission is a useful alternative for comparing the cost and effectiveness of various interventions. Several models have been developed in the past few years. They are often based on strong hypotheses concerning the population structure. This review presents compartmental and individual-based models to underline their strengths and limits in the context of HCV infection among PWID. The final section discusses the main results of the papers.

A model of bi-mode transmission dynamics of hepatitis C with optimal control

In this paper, we present a rigorous mathematical analysis of a deterministic model for the transmission dynamics of hepatitis C. The model is suitable for populations where two frequent modes of transmission of hepatitis C virus, namely unsafe blood transfusions and intravenous drug use, are dominant. The susceptible population is divided into two distinct compartments, the intravenous drug users and individuals undergoing unsafe blood transfusions. Individuals belonging to each compartment may develop acute and then possibly chronic infections. Chronically infected individuals may be quarantined. The analysis indicates that the eradication and persistence of the disease is completely determined by the magnitude of basic reproduction number R(c). It is shown that for the basic reproduction number R(c) < 1, the disease-free equilibrium is locally and globally asymptotically stable. For R(c) > 1, an endemic equilibrium exists and the disease is uniformly persistent. In addition, we present the uncertainty and sensitivity analyses to investigate the influence of different important model parameters on the disease prevalence. When the infected population persists, we have designed a time-dependent optimal quarantine strategy to minimize it. The Pontryagin's Maximum Principle is used to characterize the optimal control in terms of an optimality system which is solved numerically. Numerical results for the optimal control are compared against the constant controls and their efficiency is discussed.

Comparing parasitological vs serological determination of Schistosoma haematobium infection prevalence in preschool and primary school-aged children: implications for control programmes

To combat schistosomiasis, the World Health Organization (WHO) recommends that infection levels are determined prior to designing and implementing control programmes, as the treatment regimens depend on the population infection prevalence. However, the sensitivity of the parasitological infection diagnostic method is less reliable when infection levels are low. The aim of this study was to compare levels of Schistosoma haematobium infection obtained by the parasitological method vs serological technique. Infection levels in preschool and primary school-aged children and their implications for control programmes were also investigated. Infection prevalence based on serology was significantly higher compared with that based on parasitology for both age groups. The difference between infection levels obtained using the two methods increased with age. Consequentially, in line with the WHO guidelines, the serological method suggested a more frequent treatment regimen for this population compared with that implied by the parasitological method. These findings highlighted the presence of infection in children aged ⩽5 years, further reiterating the need for their inclusion in control programmes. Furthermore, this study demonstrated the importance of using sensitive diagnostic methods as this has implications on the required intervention controls for the population.

Modelling the prevalence of HCV amongst people who inject drugs: an investigation into the risks associated with injecting paraphernalia sharing

BACKGROUND

In order to prevent the spread of the hepatitis C virus (HCV) amongst people who inject drugs (PWID), it is imperative that any injecting risk behaviour which may contribute to the transmission of disease has its role quantified. To inform public health organisations, mathematical modelling techniques were used to explore the risk of HCV infection through the sharing of injecting paraphernalia (including filters, cookers and water).

METHODS

A mathematical model was developed for the spread of HCV based on the injecting behaviour of PWID in Scotland, with transmission occurring through the sharing of needles/syringes and other injecting paraphernalia. Numerical simulations were used to estimate the transmission probability for HCV through the sharing of injecting paraphernalia such that the modelled endemic HCV prevalence fitted with that observed amongst PWID in Scotland.

RESULTS

The transmission probability of HCV through injecting paraphernalia was modelled to be over 8 times lower than that through needles/syringes (approximately 0.19-0.30% and 2.5%, respectively), assuming transmission occurs through a combination of at least filters and cookers. In the context of reported needle/syringe and paraphernalia sharing rates in Scotland, it is estimated that 38% and 62% of HCV infections are contributed by these practices, respectively. If needle/syringe sharing rates were to be twice those reported, the contributions would be 70% and 30%, respectively.

CONCLUSION

Given that the sharing of injecting paraphernalia among PWID is common, HCV transmission through this route could be contributing to the growing healthcare burden associated with this chronic disease. Every effort should therefore be made to establish (a) the contribution that paraphernalia sharing is making to the spread of HCV, and (b) the effectiveness of services providing sterile paraphernalia in preventing infection.

Assessment of risky injection practices associated with hepatitis B, hepatitis C, and human immunodeficiency virus and using the blood-borne virus transmission risk assessment questionnaire

Risky injection practices among injection drug users (IDUs) contribute to the spread of blood-borne infections such as human immunodeficiency virus, hepatitis B, and hepatitis C. The Blood-borne Virus Transmission Risk Assessment Questionnaire (BBV-TRAQ). was developed in Australia to determine risk behaviors for specific infections. Blood testing for human immunodeficiency virus, hepatitis B, and hepatitis C was performed on all participants, and data on blood tests were linked to questionnaires. The BBV-TRAQ was administered to 242 current and former injection drug users in Long Beach, California, and the Long Beach data were compared with the original Australian data. In the comparison of the mean scores on the three subscales and total scores on the BBV-TRAQ between the samples, means for all three subscales and the total BBV-TRAQ score were significantly different, with Long Beach scores consistently lower than the Australian sample. The injecting and sexual risk subscales were significantly different across levels of AIDS risk perception for all three types of injectors; however, the other skin penetration practices subscale had no significant association with AIDS risk perception for any of the injection drug user groups. Despite recent efforts to educate injectors about the risks associated with practices captured by the other skin penetration practices subscale, such as tattooing and sharing razors, this subscale does not have an association with AIDS risk perception. injection drug users in Australia may have better access to health care, giving their self-report of infection greater validity than the California sample.

Hepatitis C virus infection in the Middle East and North Africa "MENA" region: injecting drug users (IDUs) is an under-investigated population

PURPOSE

Investigation of the injecting drug users (IDUs) population is becoming extremely critical and timely in light of the recent evidence that IDUs now act as the core of hepatitis C virus (HCV) epidemics in developed countries. The purpose of this article, therefore, is not only to review the epidemiology of HCV in the Middle East and North Africa (MENA) region, but also to see whether IDUs were adequately studied and whether harm reduction strategies to be applied for their protection have been set.

METHODS

A literature review was carried out of articles published within the last decade on HCV infection.

RESULTS

The gathered data showed that the population of IDUs is severely under-investigated throughout the whole region, possibly due to religious and cultural impediments.

CONCLUSION

In order to reduce the risk of HCV infection in IDUs, a set of recommendations are advanced emphasizing the urgent need for bio-behavioral studies in this population in order to help identify the source and mode of transmission and the genotypes of HCV involved. These results may allow the development of effective and, yet, socially acceptable intervention strategies. We believe that the role which IDUs play in sustaining HCV infection is also an under-investigated topic in many developing countries. Similar reviews and, hence, interventions should be initiated in these regions.

Hepatitis C transmission in injection drug users: could swabs be the main culprit?

Prevention programs for intravenous drug users have proven their efficacy in decreasing human immunodeficiency virus transmission but have limited effect on hepatitis C virus (HCV) contamination. A study was conducted to document the presence of HCV genome (HCV RNA) in 620 items of used injecting paraphernalia collected from representative sites. Using sensitive molecular techniques, HCV RNA was not detected on used filters or water vials and was seldom detected on cups (9%). However, HCV RNA was frequently found on syringe pools (38%) and on swabs (82%) at high titers. Our investigation, which was conducted in real injecting settings, highlights swabs as a potential source for HCV transmission.

Estimating the force of infection for HCV in injecting drug users using interval-censored data

Injecting drug users (IDUs) account for most new HCV infections. The objectives of this study were: to estimate the force of infection for hepatitis C virus in IDUs within the interval-censoring framework and to determine the impact of risk factors such as frequency of injection, drug injected, sharing of syringes and time of first injection on the time to HCV infection. We used data from the Amsterdam Cohort Study collected in The Netherlands and focused on those individuals who were HCV negative upon entry into the study. Based on the results, the force of infection was found to vary with time of first injection. The risk of infection was higher in the first 3 years of an IDU's career, implying estimates based on single cross-sectional studies could be biased. Frequency of injection and type of drug injected were found to be highly significant predictors, whereas sharing syringes was not.

Evolution of HCV incidence in drug users in France

Over the last 40 years, the dynamics of hepatitis C virus (HCV) infection in drug users has been affected by the illicit drug market, the health environment including the devastating impact of the HIV/AIDS epidemic which erupted in the 1980s, and the diffusion of substitution treatment beginning in 1995. The purpose of this literature review is to present the dynamics of HCV infection in drug users in France over the last 40 years. Two prevalence studies of HCV infection in the general population were conducted by the French Institute for Public Health Surveillance in 1994 and 2004 and were the touchstone data sources for this analysis. Hypotheses constructed from the findings of these two studies were examined in light of results reported by multicentre prevalence and incidence studies in drug-user populations. The incidence of HCV infection in drug users in France reached a peak in the late 1980s or early 1990s after a lengthy period of epidemic expansion. Implementation of a risk reduction policy enabled a very significant reduction in the incidence of HCV infection in drug users over the last 20 years, leading to incidence figures which are now 10–15% of the 1990 estimate.

Modeling the effect of high dead-space syringes on the human immunodeficiency virus (HIV) epidemic among injecting drug users

AIMS

To illustrate the impact of different proportions of injecting drug users (IDUs) sharing high dead-space syringes (HDSS) or low dead-space syringes (LDSS) on the probability of human immunodeficiency virus (HIV) transmission; and thus the impact on injection-related HIV prevalence and incidence.

DESIGN

A stochastic mathematical model was used to evaluate the impact of HDSS use in high- and low-risk IDU populations. Model parameters were obtained from peer-reviewed publications. Analytical solutions of a simplified deterministic model were obtained to explain the effect of HDSS on HIV endemic states.

FINDINGS

Simulation analysis shows that the HIV epidemic could be sustained even when a small percentage of sharing (10%) involved HDSS. The effect is much stronger in high-risk compared with low-risk populations. Steady state HIV prevalence increases with the proportion of HDSS, and for high- and low-risk populations reaches around 80% and 20%, respectively. For low-risk populations, the use of LDSS could result in the virtual elimination of HIV. These results are dependent upon an evidence-supported assumption of a significant difference in HIV transmission risk associated with HDSS versus LDSS.

CONCLUSIONS

Our models suggest that injection-related HIV epidemics may not occur when most (e.g. 95% or more) IDUs use LDSS. While these results are based on indirect risk measures and a number of simplifying assumptions, the effect of blood retained in high dead-space syringes on HIV prevalence seems to be very strong, even using relatively conservative assumptions. The findings have potential implications for needle exchange programs and the types of syringes produced and distributed world-wide.

Seventy-five years of estimating the force of infection from current status data

The force of infection, describing the rate at which a susceptible person acquires an infection, is a key parameter in models estimating the infectious disease burden, and the effectiveness and cost-effectiveness of infectious disease prevention. Since Muench formulated the first catalytic model to estimate the force of infection from current status data in 1934, exactly 75 years ago, several authors addressed the estimation of this parameter by more advanced statistical methods, while applying these to seroprevalence and reported incidence/case notification data. In this paper we present an historical overview, discussing the relevance of Muench's work, and we explain the wide array of newer methods with illustrations on pre-vaccination serological survey data of two airborne infections: rubella and parvovirus B19. We also provide guidance on deciding which method(s) to apply to estimate the force of infection, given a particular set of data.

A national cross-sectional study among drug-users in France: epidemiology of HCV and highlight on practical and statistical aspects of the design

Background

Epidemiology of HCV infection among drug users (DUs) has been widely studied. Prevalence and sociobehavioural data among DUs are therefore available in most countries but no study has taken into account in the sampling weights one important aspect of the way of life of DUs, namely that they can use one or more specialized services during the study period. In 2004–2005, we conducted a national seroepidemiologic survey of DUs, based on a random sampling design using the Generalised Weight Share Method (GWSM) and on blood testing.

Methods

A cross-sectional multicenter survey was done among DUs having injected or snorted drugs at least once in their life. We conducted a two stage random survey of DUs selected to represent the diversity of drug use. The fact that DUs can use more than one structure during the study period has an impact on their inclusion probabilities. To calculate a correct sampling weight, we used the GWSM. A sociobehavioral questionnaire was administered by interviewers. Selected DUs were asked to self-collect a fingerprick blood sample on blotting paper.

Results

Of all DUs selected, 1462 (75%) accepted to participate. HCV seroprevalence was 59.8% [95% CI: 50.7–68.3]. Of DUs under 30 years, 28% were HCV seropositive. Of HCV-infected DUs, 27% were unaware of their status. In the month prior to interview, 13% of DUs shared a syringe, 38% other injection parapharnelia and 81% shared a crack pipe. In multivariate analysis, factors independently associated with HCV seropositivity were age over 30, HIV seropositivity, having ever injected drugs, opiate substitution treatment (OST), crack use, and precarious housing.

Conclusion

This is the first time that blood testing combined to GWSM is applied to a DUs population, which improve the estimate of HCV prevalence. HCV seroprevalence is high, indeed by the youngest DUs. And a large proportion of DUs are not aware of their status. Our multivariate analysis identifies risk factors such as crack consumption and unstable housing.

Undiagnosed hepatitis C on the general medicine and trauma services of two urban hospitals

The inpatient medical service may be an important location to identify undiagnosed hepatitis C virus (HCV) infection. We conducted a cross-sectional HCV prevalence study in consecutive patients aged 18-65 admitted in a three-month period to two urban hospitals' general internal medicine and trauma services. Patient sera were anonymously screened for anti-HCV antibody with an enzyme-linked immunoassay and, when anti-HCV positive (+), for HIV. Health system records were examined for prior HCV testing or diagnosis or an HIV diagnosis then linked anonymously to test results. Multivariate logistic regression was used to examine associations of patient and health care factors with unknown HCV+ status. Of 786 unique patients tested (60.3% of all admitted patients), 62 (7.9%) were HCV+ without a prior HCV+ test or diagnosis while 61 patients (7.8%) tested HCV+ but had prior HCV+ test or diagnosis. Of 62 patients with unknown HCV+, 6 (9.7%) were HIV+ but only 3 had a prior HIV diagnosis; of 61 patients with known HCV+, all 9 (14.8%) HIV+ had been diagnosed. Among the 640 patients with prior unknown HCV status, an HCV+ test was strongly associated with age: 50-65 (adjusted odds ratio [AOR] 5.44, CI 2.20-13.48) and age 36-49 (AOR 4.65, CI 1.91-11.32) versus. 18-35. In this anonymous study, we could not obtain HCV risk factor data but the positive and negative predictive values of HCV testing all inpatients with an unknown HCV status were 99.3% and 99.0%, respectively. In similar urban general medicine and trauma services, broader efforts to test for HCV in inpatients aged 36-65 may be warranted.

Pilot trial of an intervention aimed at modifying drug preparation practices among injection drug users in Puerto Rico

Injection drug users (IDUs) contaminate preparation materials with blood-borne pathogens by using syringes as measuring and dispensing devices. In collaboration with IDUs, we developed a preventive intervention consisting of four new preparation practices aimed at avoiding the use of syringes in the preparation, and reducing the contamination of the materials. This report describes the results of a pilot trial introducing the new practices to ascertain their adoption potential and their potential efficacy in reducing contamination. Participants comprised 37 active IDUs among whom the new practices were promoted during 16 weeks. In addition to self-reported behaviors, the study collected cookers and plastic caps from shooting galleries and tested them for the presence of blood residues. Adoption rates were: (1) cleaning of skin area with hand sanitizer--65.6%; (2) directly pouring water with a dropper into the cooker--56.3%; (3) drawing drug solution with a preparation syringe and syringe filter--34.4%; and, (4) backload rinsing syringes--53.1%. Rates of blood residues detected in cookers and plastic caps were 41.7% prior to the trial, 28.6% at week 8, 24.6% at week 14, and 12.0% at week 18. We believe the results of the pilot trial are compelling and suggest that this intervention merits further formal testing.

Potential impact of vaccination on the hepatitis C virus epidemic in injection drug users

BACKGROUND

Hepatitis C virus (HCV) causes significant morbidity and mortality in injecting drug users (IDU) worldwide. HCV vaccine candidates have shown promise for reducing the infectivity of acute infection and averting chronic infection, yet the impact of varying levels of vaccine efficacy and vaccine delivery strategies on the HCV epidemic in IDU have not been explored.

METHODS

We utilized extensive data on injecting behavior collected in the UFO Study of young IDU in San Francisco to construct a stochastic individual-based model that reflects heterogeneous injecting risk behavior, historical HCV trends, and existing information on viral dynamics and vaccine characteristics.

RESULTS

Our modeled HCV rate closely paralleled observed HCV incidence in San Francisco, with estimated incidence of 59% per person year (ppy) early in the epidemic, and 27% ppy after risk reduction was introduced. Chronic HCV infection, the clinically relevant state of HCV infection that leads to liver disease and hepatocellular cancer, was estimated at 22% ppy (± 3%) early in the epidemic and 14% ppy (± 2%) after risk reduction was introduced. We considered several scenarios, and highlight that a vaccine with 50% to 80% efficacy targeted to high-risk or sero-negative IDU at a high vaccination rate could further reduce chronic HCV incidence in IDU to 2-7% ppy 30 years after its introduction.

CONCLUSIONS

Our results underscore the importance of further efforts to develop both HCV vaccines and optimal systems of delivery to IDU populations.

Meta-regression of hepatitis C virus infection in relation to time since onset of illicit drug injection: the influence of time and place

The authors examined the relation between time since onset of illicit drug injection (time at risk) and rates of hepatitis C virus (HCV) infection by using meta-regression. In 72 prevalence studies, median time since onset of injection was 7.24 years and median prevalence was 66.02%. The model showed statistically significant linear and quadratic effects of time at risk on HCV prevalence and significantly higher prevalence in developing and transitional countries and in earlier samples (1985-1995). In developed countries post-1995, mean fitted prevalence was 32.02% (95% confidence interval: 25.31, 39.58) at 1 year of injection and 53.01% (95% confidence interval: 40.69, 65.09) at 5 years. In developing/transitional countries post-1995, mean fitted HCV prevalence was 59.13% (95% confidence interval: 30.39, 82.74) at 1 year of injection. In 10 incidence studies, median time at risk was 5.29 years and median cumulative HCV incidence was 20.69%. Mean fitted cumulative incidence was 27.63% (95% confidence interval: 16.92, 41.70) at 1 year of drug injection. The authors concluded that time to HCV infection in developed countries has lengthened. More rapid onset of HCV infection in drug injectors in developing/transitional countries resembles an earlier era of the HCV epidemic in other regions.

A comparison between the force of infection estimates for blood-borne viruses in injecting drug user populations across the European Union: a modelling study

A number of studies have been conducted in injecting drug user (IDU) populations in Europe, in which the prevalence of human immunodeficiency virus (HIV), hepatitis B virus (HBV) and hepatitis C virus (HCV) was measured together with demographic and epidemiological information such as age and the age at first injection. A measure of the risk of becoming infected is the force of infection (FOI), defined as the per capita rate at which susceptible individuals acquire infection. The objective of this study was to estimate the FOI and its heterogeneity for HBV, HCV and HIV (where available) for IDU populations in a number of countries in Europe. Data were obtained from five countries: Belgium, the United Kingdom, Spain and Italy, and the Czech Republic, which provided two data sets. The model describes the prevalence of infection as a function of the FOI that may vary over time or duration of IDU. In addition to this, if two or more infections were being considered then a parameter describing the potential heterogeneity of the FOI within the IDU population was also estimated. The results here add to the growing evidence that new initiates to injecting are at an increased risk of blood-borne viral infection compared with more experienced IDUs. In addition, there is evidence of individual heterogeneity of FOI estimates within the overall IDU populations. This suggests that different proportions of individuals in each population are at increased risk of infection compared with the rest of the population. Future interventions should identify and target these individuals. Moreover, changes over time in individual heterogeneity estimates of IDU populations may provide an indicator for measuring intervention impacts.

New challenges for mathematical and statistical modeling of HIV and hepatitis C virus in injecting drug users

Injecting drug users are not only driving blood-borne transmission of HIV and hepatitis C virus but also likely drive sexual transmission of HIV in large parts of the world. Mathematical and statistical modeling can provide important insights in these epidemiological processes and on the potential impact of interventions but have been little used to date. This review aims to discuss the potential areas of application of modeling in the field of viral infections in injecting drug users. After reviewing key examples of published modeling work on HIV and hepatitis C virus in injecting drug users, we discuss recent developments in the epidemiology, diagnosis, treatment and prevention of these infections. In particular, new methods for the diagnosis of early HIV infection, new antivirals for a more effective treatment of HIV, hepatitis B and hepatitis C virus infections, new concepts in design and surveillance of interventions for drug users and increasing possibilities of molecular typing of pathogens are changing the questions and decisions for public health policy makers who deal with drug-related infectious diseases. Research including mathematical modeling is needed to understand the impact of new diagnostic tools, new treatment options and combined intervention strategies on the epidemiology of viral infections in injecting drug users. Methodological advances in mathematical modeling are required to adequately approach some of the ensuing research questions. Modeling has much to offer for solving urgent policy questions, but current levels of funding in modeling research are insufficient and need to be scaled up to make better use of these possibilities.

Hepatitis C and human immunodeficiency virus risk behaviors in polydrug users on methadone maintenance

We examined the impact of methadone maintenance treatment (MMT) on risk behaviors for transmission of blood-borne diseases in polydrug users who had tested positive or negative for hepatitis C virus (HCV). At intake, HCV-positive participants (n=362) engaged in more human immunodeficiency virus (HIV) risk behaviors (as measured by the HIV Risk-Taking Behavior Scale) than HCV-negative participants (n=297; p< .001). This difference was specific to injection-related behaviors and decreased significantly within the first few weeks of MMT (p< .0001). Where needles continued to be used, HCV-positive participants became more likely over time to engage in safer injecting practices. Furthermore, HCV-positive participants became more likely to use condoms than HCV-negative participants. These findings demonstrate that both drug- and sex-related risk behaviors decrease during MMT and emphasize the benefits of methadone programs for public health and HIV/HCV prevention.

Fentanyl use among street drug users in Toronto, Canada: behavioural dynamics and public health implications

Prescription opioids (POs) are playing an increasingly central role in street drug use and related harms in North America. One distinct PO substance of interest is Fentanyl (Duragesic), a potent opioid analgesic designed for transdermal time-release application. Studies from Europe and North America have documented the sizeable overdose and mortality burden associated with the non-medical use of this drug. This study explores practices and risk dynamics associated with Fentanyl abuse, also considering public health implications. Semi-structured interviews were conducted with 25 regular street-entrenched illicit PO users in Toronto, Canada, a sub-sample of which were recent Fentanyl users. Results showed that while relatively rare on the illicit PO market in Toronto, Fentanyl is a highly desired, sought after and relatively expensive PO drug among street users. In addition, the new 'matrix' patch technology implemented for Fentanyl since 2005 is a limited safeguard against abuse as simple extraction methods are utilized by street users. Finally, distinct risk behaviours relevant for public health emerge due to the high black market costs of Fentanyl and the extraction techniques applied, potentially facilitating high risks for infectious disease (e.g., HCV, HIV) transmission and/or overdose. Consequently, prevalence and practices of Fentanyl use by street users require closer monitoring, targeted interventions and further research regarding risks and outcomes.

The epidemic history of hepatitis C among injecting drug users in Flanders, Belgium

We employed recently developed statistical methods to explore the epidemic behaviour of hepatitis C subtype 1a and subtype 3a among injecting drug users (IDUs) in Flanders, Belgium, using new gene sequence data sampled among two geographically distinct populations of IDUs. First the extent of hepatitis C transmission across regions/countries was studied through calculation of association indices. It was shown that viral exchange had occurred between both populations in Flanders as well as across international borders. Furthermore, evidence was found suggestive of subtypes 1a and 3a predominantly circulating in subpopulations of Flemish IDUs, exhibiting different degrees of travelling/migration behaviour. Secondly, through coalescent-based analysis the viral epidemic history of the hepatitis C subtype 1a and 3a epidemics was inferred. Evidence was found for different dynamic forces driving both epidemics. Moreover, results suggested that the hepatitis C subtype 3a epidemic has reached a steady state, while the hepatitis C 1a epidemic has not, which therefore might become the predominant subtype among IDUs.

Risk of hepatitis C virus transmission through drug preparation equipment: a systematic and methodological review

The use of blood-contaminated drug preparation equipment is believed to be associated with the transmission of hepatitis C virus (HCV) among injection drug users (IDUs), but the extent of HCV infection risk is unclear. The objective of this review was to appraise the evidence regarding HCV incidence associated with the use of drug preparation equipment such as drug mixing containers, filters and water. In June 2007, cohort and case-control studies examining the association of HCV incidence with the sharing of drug preparation equipment were identified by searching electronic reference databases as well as the reference lists of published papers. Ten studies (seven cohort and three nested case-control) met the inclusion criteria for the review. The relative risk of HCV infection associated with drug preparation equipment were mainly between 2.0 and 5.9; however, the precision of the estimates from individual studies were marked by wide confidence intervals. Few studies exist to allow an adequate assessment of the individual contributions of containers, filters and water to HCV incidence. The major methodological limitations of reviewed studies were short follow-up times, inadequate control of confounders and lack of exclusion of periods when IDUs were not at risk for HCV infection through drug injection. Current evidence implicating the association of drug preparation equipment with HCV incidence is limited by several methodological concerns.

The changing epidemiology of hepatitis C virus infection in Europe

The epidemic of hepatitis C virus (HCV) infection in Europe is continuously evolving and epidemiological parameters (prevalence, incidence, disease transmission patterns and genotype distribution) have changed substantially during the last 15 years. Four main factors contribute to such changes: increased blood transfusion safety, improvement of healthcare conditions, continuous expansion of intravenous drug use and immigration to Europe from endemic areas. As a result, intravenous drug use has become the main risk factor for HCV transmission, prevalent infections have increased and genotype distribution has changed and diversified. Hence, prevalence data from studies conducted a decade ago may not be useful to estimate the current and future burden of HCV infection and additional epidemiological studies should be conducted, as well as new preventive strategies implemented to control the silent epidemic. This review summarizes recently published data on the epidemiology of HCV infection in Europe focusing on the factors currently shaping the epidemic.

Hepatitis C virus (HCV) prevalence, and injecting risk behaviour in multiple sites in England in 2004

We sought to corroborate geographical differences in hepatitis C virus (HCV) prevalence and assess whether these can be explained by differences in injecting risk behaviour. A community recruited interview survey of 1058 injecting drug users (IDU) - including a blood spot specimen for antibody testing - was undertaken in seven cities in England. HCV prevalence varied from 27% to 74% across sites (chi(2)(6) = 115.3, P < 0.001). There was a significant variation in crack-injection, prison history, injecting frequency, homelessness, groin injecting, syringe reuse and sharing between the sites. Adjustment for clustering by site and other covariates attenuated the odds ratios (OR) for most variables: e.g. crack injection changed from an unadjusted OR of >2 to an adjusted OR of 1.4 (95% CI 0.9-2.0). Remaining significant covariates included: homelessness (OR 2.2; 1.4-3.6); ever imprisonment (OR 1.7; 1.2-2.5); syringe sharing >18 months ago (OR 2.0; 1.3-3.0); injecting duration and age. Introducing site as a second level variable did not reach significance (P = 0.10). HCV prevalence among IDU reporting 'never sharing' was 48%. Geographical variation in HCV prevalence remains poorly explained, but should be the key focus of our surveillance effort. Measures of sharing and their interpretation require greater scrutiny.