Global, regional, and national estimates of hepatitis C virus (HCV) infection incidence among people who inject drugs and number of new annual HCV infections attributable to injecting drug use: a multi-stage analysis

BACKGROUND

Measuring progress towards the WHO 2030 target for hepatitis C virus (HCV) elimination among people who inject drugs (PWID)-an incidence of two or fewer infections per 100 person-years-has been challenging due to insufficient data. We aimed to estimate HCV incidence among PWID before and since 2015, progress towards the 2030 target, and the number of new annual HCV infections attributable to injecting drug use since 2015.

METHODS

Four sequential steps were taken to estimate country-specific HCV incidence. First, we estimated HCV incidence from HCV antibody prevalence by duration of injecting using force-of-infection (FOI) modelling. Second, using Bayesian random-effects meta-analysis, we pooled FOI-derived estimates with any direct HCV incidence estimates from a published global meta-analysis, by country. Third, for countries with no FOI-derived or direct HCV incidence data, we applied incidence estimates from a published multi-country dynamic mathematical model. Fourth, for countries for which incidence could not be estimated using any of the aforementioned methods but that had data on overall HCV antibody prevalence (ie, not stratified by duration of injecting), we used a regression model to predict incidence based on prevalence and average duration of injecting. WHO regional and global HCV incidence, incidence rate ratios (IRRs) for 2015-21 versus pre-2015, and relative decline needed to achieve the 2030 WHO target were derived and weighted by the country-specific number of PWID at risk (ie, those who were HCV RNA-negative), provided that data from at least five countries were available within a WHO region. New annual HCV infections attributable to injecting drug use were estimated by multiplying country-specific HCV incidence for the 2015-21 period by the number of HCV RNA-negative PWID; for countries with no HCV incidence data but with evidence of an existing PWID population, incidence was imputed using the corresponding WHO regional incidence.

FINDINGS

For the pre-2015 period, 146 HCV incidence estimates from 81 countries were included: 52 (36%) direct, 61 (42%) FOI-derived, and 33 (23%) regression-based estimates. For 2015-21, 114 estimates from 97 countries were included: 20 (18%) direct, 18 (16%) FOI-derived, 68 (60%) dynamic model-derived, and eight (7%) regression-based. Globally, pooled HCV incidence was 13·9 per 100 person-years (95% uncertainty interval [UI] 11·9-16·4) for pre-2015 and 8·6 per 100 person-years (7·1-10·7) for 2015-21. Based on a subset of countries with data for both periods, incidence was lower in the Western Pacific (IRR 0·32 [95% UI 0·23-0·50]), Eastern Mediterranean (0·67 [0·50-0·89]), and European (0·79 [0·63-1·02]) regions in 2015-21 versus pre-2015, but no difference was observed in the Americas. Insufficient data prevented comparisons over time for the African and South-East Asia regions and globally. Based on 2015-21 HCV incidence, the global decline needed to meet the 2030 WHO target is 76·7% (95% UI 71·8-81·3), while the global number of new annual HCV infections attributable to injecting drug use was 833 760 (95% UI 493 716-1 544 395) among the 187 countries with documented evidence of a population of PWID.

INTERPRETATION

A substantial increase in HCV treatment and prevention is needed globally to achieve the WHO 2030 HCV elimination target for incidence among PWID.

FUNDING

WHO and the Wellcome Trust.

Methods and indicators to validate country reductions in incidence of hepatitis C virus infection to elimination levels set by WHO

One of the main goals of the 2016 Global Health Sector Strategy on viral hepatitis is the elimination of hepatitis C virus (HCV) as a public health problem by 2030, defined as an 80% reduction in incidence and 65% reduction in mortality relative to 2015. Although monitoring HCV incidence is key to validating HCV elimination, use of the gold-standard method, which involves prospective HCV retesting of people at risk, can be prohibitively resource-intensive. Additionally, few countries collected quality data in 2015 to enable an 80% decrease by 2030 to be calculated. Here, we first review different methods of monitoring HCV incidence and discuss their resource implications and applicability to various populations. Second, using mathematical models developed for various global settings, we assess whether trends in HCV chronic prevalence or HCV antibody prevalence or scale-up levels for HCV testing, treatment, and preventative interventions can be used as reliable alternative indicators to validate the HCV incidence target. Third, we discuss the advantages and disadvantages of an absolute HCV incidence target and suggest a suitable threshold. Finally, we propose three options that countries can use to validate the HCV incidence target, depending on the available surveillance infrastructure.

A comparison of two biological markers of recent hepatitis C virus (HCV) infection: implications for the monitoring of interventions and strategies to reduce HCV transmission among people who inject drugs

BackgroundMonitoring hepatitis C virus (HCV) incidence is important for assessing intervention impact. Longitudinal studies of people who inject drugs (PWID), using repeated biological tests, are costly; alternatively, incidence can be estimated using biological markers of recent infection in cross-sectional studies.AimWe aimed to compare incidence estimates obtained from two different biological markers of recent infection in a cross-sectional study to inform monitoring approaches for HCV elimination strategies.MethodSamples from an unlinked anonymous bio-behavioural survey of PWID were tested for two recent infection markers: HCV RNA with anti-HCV negative ('RNA') and low-avidity anti-HCV with HCV RNA present ('avidity'). These two markers were used separately and in combination to estimate HCV incidence.ResultsBetween 2011 and 2013, 2,816 anti-HIV-negative PWID (25% female) who had injected during the preceding year were either HCV-negative or had one of the two markers of recent infection: 57 (2.0%) had the RNA marker and 90 (3.2%) the avidity marker. The two markers had similar distributions of risk and demographic factors. Pooled estimated incidence was 12.3 per 100 person-years (pyrs) (95% credible interval: 8.8-17.0) and not significantly different to avidity-only (p = 0.865) and RNA-only (p = 0.691) estimates. However, the RNA marker is limited by its short duration before anti-HCV seroconversion and the avidity marker by uncertainty around its duration.ConclusionBoth markers have utility in monitoring HCV incidence among PWID. When HCV transmission is high, one marker may provide an accurate estimate of incidence; when it is low or decreasing, a combination may be required.

HCV seroconversion in a cohort of people who use drugs followed in a mobile harm reduction unit in Madrid: Breaking barriers for HCV elimination

Background and aims

Harm reduction strategies have been shown to decrease the incidence of human immunodeficiency virus (HIV) infection in people who inject drugs (PWID), but the results have been inconsistent when it comes to prevention of hepatitis C virus (HCV) infection. We aimed to examine the rate of HCV seroconversion among people who use drugs (PWUD) followed at a mobile harm reduction unit (MHRU) to evaluate if a low-threshold methadone substitution program (LTMSP) is associated with a low HCV seroconversion rate and subsequently identify barriers for elimination.

Materials and methods

A cohort of PWUD have been followed at a MRHU in Madrid between 2013 and 2016. Individuals who were negative for HCV antibodies at baseline and who had at least one retest for HCV antibodies were eligible. Kaplan-Meier methods were employed to estimate the global incidence density.

Results

During the study period, 946 PWUD were screened for HCV at least once. At baseline 127 PWUD were negative for HCV antibodies and had at least one follow-up HCV antibodies test. The baseline HCV prevalence was 33%. After a median 0.89 (IQR 0.3–1.5) years of follow-up and 135 person-years of risk for HCV infection, 28 subjects seroconverted. The incidence density for HCV seroconversion for this sample was 20.7 cases (95% CI: 14.3–29.7) per 100 person-years. Injecting drugs in the last year was strongly associated to HCV seroconversion (AHR 15.5, 95%CI 4.3–55.8, p < 0.001). Methadone status was not associated to HCV seroconversion.

Conclusions

A high incidence of HCV infection was found among PWUD at a MHRU in Madrid. In this setting opiate substitutive treatment (OST) as a LTMSP does not appear to protect against HCV seroconversion.

Current and recent drug use intensifies sexual and structural HIV risk outcomes among female sex workers in the Russian Federation

BACKGROUND

Female sex workers (FSW) and people who inject drugs (PWID) are at high risk for HIV infection, with FSW-PWID at even greater risk. HIV-related research often focuses on the primary mode of transmission - sexual or parenteral transmission for FSW and PWID, respectively - with less known on how sex work and injection drug use (IDU) are collectively associated with the risk environment experienced by sex workers. We investigated this relationship among FSW in three Russian cities.

METHODS

In 2011, FSWs (N=754) in Tomsk, Krasnoyarsk, and Kazan were recruited via respondent-driven sampling and completed a survey and rapid HIV screening. Multivariable models evaluated the role of injection history (classified as active: last 6 months, former: prior to last 6 months, and never) with a set of sexual and structural HIV risk outcomes.

RESULTS

IDU was common: 11% actively injected drugs and 11% were former injectors. HIV infection was most prevalent among active injectors (AOR: 6.7; 95% CI: 2.4-18.9) and former injectors (AOR:4.5; 95%CI: 1.7-11.6), compared to non-injectors. Some 6-8% of non-injecting FSWs reported recent physical or sexual client violence and 23% police extortion. Compared to these non-injectors, active injecting was associated with unprotected anal sex (AOR: 2.8, 95%CI: 1.2-6.4), client violence (AOR: 7.3, 95%CI: 2.1-24.7), and police extortion (AOR: 3.0 95%CI: 1.5-5.9%). Self-reported sexual and structural risk outcomes were also more prevalent among active compared to former injectors; however, few differences existed between former and non-injectors.

CONCLUSIONS

FSW experience sexual, structural, and HIV risk outcomes and these risks are amplified for actively injecting FSWs. FSW who stopped injecting drugs demonstrated risk profiles closer to those of sex workers who had no history of injection. HIV prevention programs and outreach can provide opportunities to include harm reduction interventions and linkage to treatment for FSW to move FSWs towards lower risk environments.

Exploration of genetically determined resistance against hepatitis C infection in high-risk injecting drug users

Genetic resistance to specific infections is well recognized. In hepatitis C virus (HCV) infection, genetic polymorphisms in IL-28B and the killer cell immunoglobulin-like receptors (KIR) and their HLA class I ligands have been shown to affect clearance of the virus following infection. There are limited data regarding resistance to established HCV infection. Reliable quantification of repeated exposure in high-risk populations, such as injecting drug users (IDU), is a key limitation of previous studies of resistance. Behavioural data and DNA from IDU (n = 210) in the Hepatitis C Incidence and Transmission Study in prisons (HITS-p) cohort were genotyped for polymorphisms in: IL-28B, peptidyl-prolyl isomerase A (PPIA), HLA-C and KIR2. To quantify risk, a composite risk index based on factors predictive of incident HCV infection was derived. Logistic regression analysis revealed the risk index was strongly associated with incident HCV infection (P < 0.0001). The upper tertile of the uninfected individuals had risk indices comparable to the incident cases, but remained uninfected. There were no significant differences in the frequencies of IL-28B or PPIA polymorphisms between these exposed-uninfected cases, or in the frequencies of KIR2-DL3, HLA-C1, or their combination. A framework for the investigation of genetic determinants of resistance to HCV infection has been developed. Several candidate gene associations were investigated and excluded. Further investigation of genetic determinants of resistance to HCV infection is warranted.

Identifying newly acquired cases of hepatitis C using surveillance: a literature review

Surveillance of newly acquired hepatitis C virus (HCV) infection is crucial for understanding the epidemiology of HCV and informing public health practice. However, monitoring such infections via surveillance systems is challenging because they are commonly asymptomatic. A literature review was conducted to identify methodologies used by HCV surveillance systems to identify newly acquired infections; relevant surveillance systems in 15 countries were identified. Surveillance systems used three main strategies to identify newly acquired infections: (1) asking physicians to classify cases; (2) identifying symptomatic cases or cases with elevated alanine aminotransferases; and (3) identifying cases with documented evidence of anti-HCV antibody seroconversion within a specific time-frame. Case-ascertainment methods varied with greater completeness of data in enhanced compared to passive surveillance systems. Automated systems that extract and link testing data from multiple laboratory and clinic databases may provide an opportunity for collecting testing histories for individuals that is less resource intensive than enhanced surveillance.

Hepatitis C prevalence in injecting drug users in Europe, 1990-2007: impact of study recruitment setting

Monitoring injecting drug users' (IDUs) health is challenging because IDUs form a difficult to reach population. We examined the impact of recruitment setting on hepatitis C prevalence. Individual datasets from 12 studies were merged. Predictors of HCV positivity were sought through a multilevel analysis using a mixed-effects logistic model, with study identifier as random intercept. HCV prevalence ranged from 21% to 86% across the studies. Overall, HCV prevalence was higher in IDUs recruited in drug treatment centres compared to those recruited in low-threshold settings (74% and 42%, respectively, P < 0·001). Recruitment setting remained significantly associated with HCV prevalence after adjustment for duration of injecting and recent injection (adjusted odds ratio 0·7, 95% confidence interval 0·6-0·8, P = 0·05). Recruitment setting may have an impact on HCV prevalence estimates of IDUs in Europe. Assessing the impact of mixed recruitment strategies, including respondent-driven sampling, on HCV prevalence estimates, would be valuable.

Management of HIV and hepatitis C virus infections in resource-limited settings

PURPOSE OF REVIEW

To provide an update on the epidemiology and management of HIV and hepatitis C virus (HCV) in resource-limited settings (RLSs).

RECENT FINDINGS

The global prevalence of HIV is 33.3 million people of whom 22.5 million live in sub-Saharan Africa. Hepatitis C affects 170 million people globally with majority of the infected persons living in sub-Saharan Africa and other RLSs. Transmission of these viruses varies greatly even within the RLSs. In the RLSs in Europe, Asia and Central/South America, most transmissions occur through injection drug use, whereas in Africa use of needles for medical treatment and blood transfusion may be the main modes of transmission. However, generally there is a rise in injection drug use even in RLSs.

SUMMARY

Hepatitis C and HIV are common infections and are more prevalent in RLSs, but there are regional differences in transmission even in RLSs. Treatment is difficult in some of the RLSs and prevention by screening donor blood as well and use of sterile instruments in treatment of patients will be important in curbing transmission in some of these settings.

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.

Expanded syringe exchange programs and reduced HIV infection among new injection drug users in Tallinn, Estonia

BACKGROUND

Estonia has experienced an HIV epidemic among intravenous drug users (IDUs) with the highest per capita HIV prevalence in Eastern Europe. We assessed the effects of expanded syringe exchange programs (SEP) in the capital city, Tallinn, which has an estimated 10,000 IDUs.

METHODS

SEP implementation was monitored with data from the Estonian National Institute for Health Development. Respondent driven sampling (RDS) interview surveys with HIV testing were conducted in Tallinn in 2005, 2007 and 2009 (involving 350, 350 and 327 IDUs respectively). HIV incidence among new injectors (those injecting for < = 3 years) was estimated by assuming (1) new injectors were HIV seronegative when they began injecting, and (2) HIV infection occurred at the midpoint between first injection and time of interview.

RESULTS

SEP increased from 230,000 syringes exchanged in 2005 to 440,000 in 2007 and 770,000 in 2009. In all three surveys, IDUs were predominantly male (80%), ethnic Russians (>80%), and young adults (mean ages 24 to 27 years). The proportion of new injectors decreased significantly over the years (from 21% in 2005 to 12% in 2009, p = 0.005). HIV prevalence among all respondents stabilized at slightly over 50% (54% in 2005, 55% in 2007, 51% in 2009), and decreased among new injectors (34% in 2005, 16% in 2009, p = 0.046). Estimated HIV incidence among new injectors decreased significantly from 18/100 person-years in 2005 and 21/100 person-years in 2007 to 9/100 person-years in 2009 (p = 0.026).

CONCLUSIONS

In Estonia, a transitional country, a decrease in the HIV prevalence among new injectors and in the numbers of people initiating injection drug use coincided with implementation of large-scale SEPs. Further reductions in HIV transmission among IDUs are still required. Provision of 70 or more syringes per IDU per year may be needed before significant reductions in HIV incidence occur.