Role of HCV Viremia in Corroborated HCV Transmission Events Within Young Adult Injecting Partnerships

What Hepatitis C Virus (HCV) Diagnostic Tools Are Needed to Advance Diagnosis of Current HCV Infection in Outreach Settings and in a Nonclinical Setting?

Given the growing hepatitis C virus (HCV) epidemic in the United States, it is imperative to implement a coordinated, equitable public health approach to HCV testing that will facilitate immediate access to treatment, especially for individuals with limited healthcare access and those who inject drugs. Point-of-care RNA diagnostic tests have the greatest potential to address this need. Future regulatory approval has been facilitated by a recent change in the US Food and Drug Administration's approach to evaluating point-of-care diagnostic tests that have been developed and validated.

Optimal Frequency of Hepatitis C Virus (HCV) RNA Testing for Detection of Acute HCV Infection Among At-risk People With Human Immunodeficiency Virus: A Multicenter Study

Using 3-stage pooled-plasma hepatitis C virus (HCV) RNA testing performed quarterly among at-risk people with human immunodeficiency virus (PWH), we found that if testing had been performed every 6 or 12 months, 58.6%-91.7% of PWH who recently acquired HCV would be delayed for diagnosis and might contribute to onward HCV transmission with longer durations.

Identification of Genetically Related HCV Infections Among Self-Described Injecting Partnerships

BACKGROUND

The current opioid epidemic across the United States has fueled a surge in the rate of new hepatitis C virus (HCV) infections among young persons who inject drugs (PWIDs). Paramount to interrupting transmission is targeting these high-risk populations and understanding the underlying network structures facilitating transmission within these communities.

METHODS

Deep sequencing data were obtained for 52 participants from 32 injecting partnerships enrolled in the U-Find-Out (UFO) Partner Study, which is a prospective study of self-described injecting dyad partnerships from a large community-based study of HCV infection in young adult PWIDs from San Francisco. Phylogenetically linked transmission events were identified using traditional genetic-distance measures and viral deep sequence phylogenies reconstructed to determine the statistical support of inferences and the direction of transmission within partnerships.

RESULTS

Using deep sequencing data, we found that 12 of 32 partnerships were genetically similar and clustered. Three additional phylogenetic clusters were found describing novel putative transmission links outside of the injecting relationship. Transmission direction was inferred correctly for 5 partnerships with the incorrect transmission direction inferred in more than 50% of cases. Notably, we observed that phylogenetic linkage was most often associated with a lower number of network partners and involvement in a sexual relationship.

CONCLUSIONS

Deep sequencing of HCV among self-described injecting partnerships demonstrates that the majority of transmission events originate from outside of the injecting partnership. Furthermore, these findings caution that phylogenetic methods may be unable to routinely infer the direction of transmission among PWIDs especially when transmission events occur in rapid succession within high-risk networks.

Per-Contact Infectivity of Hepatitis C Virus Acquisition in Association With Receptive Needle Sharing Exposures in a Prospective Cohort of Young Adult People who Inject Drugs in San Francisco, California

Background

Sharing needles and ancillary injecting equipment is a primary risk exposure for hepatitis C virus (HCV) infection among people who inject drugs (PWID); however, infectivity of these exposures is not well quantified. We aimed to estimate per-event HCV infectivity associated with receptive needle sharing (RNS) among susceptible PWID.

Methods

Participants in a prospective cohort study of young adult PWID who were anti-HCV and HCV RNA negative at baseline and attended at least 2 follow-up study visits between 2003 and 2014 were eligible. Data were selected from the first HCV-negative through the first HCV-positive visit (or last HCV-negative among those uninfected). Anti-HCV and HCV-RNA tests were used to determine infection status. A probabilistic exposure model linking observed HCV infection outcomes to self-reported exposure events was applied to estimate infectivity.

Results

Among 344 participants, a maximum likelihood estimate considering RNS yielded a pooled population per RNS event HCV probability of 0.25% (95% confidence interval [CI], 0.10%–0.43%), and 1.12% (95% CI, 0.48%–2.35%) among those who acquired any HCV infection (primary or reinfection).

Conclusions

HCV is highly infectious in association with RNS, a primary injection-related risk exposure. Our infectivity estimate among participants who acquired any HCV infection is 1.7 times higher than that estimated for HIV infection in PWID and 2.24 times higher than that estimated among health care workers exposed through needle sticks. The strengths of this study include the assessment of receptive needle sharing events, the prospective design, and relatively short recall and testing periods. These results can inform transmission models and research to prevent HCV infection.

HCV incidence is associated with injecting partner age and HCV serostatus mixing in young adults who inject drugs in San Francisco

BACKGROUND

HCV incidence is increasing in the US, notably among younger people who inject drugs (PWID). In a cohort of young adult (age<30 years) PWID in San Francisco we examined whether 'injecting partner mixing' factors, i.e. age of partner and knowledge of their HCV serostatus, were associated with HCV transmission.

METHODS

In 448 susceptible PWID studied prospectively. All participants were asked to report characteristics and behaviors they engaged in with up to 3 injecting partners defined as "people whom you injected the most with" in the past month". These partnerships did not specify that drugs or injecting equipment was shared. HCV incidence was estimated by age of up to 3 injecting partners, categorized as: (i) all <30; (ii) mixed-age (<&≥30); and (iii) all ≥30 years and perceived knowledge of the HCV status of participants' injecting partners' HCV status. Interaction was evaluated between partnership age categories and perceived HCV status of partners.

RESULTS

Between 2006-2018, overall HCV incidence (/100 person years observation [pyo]) was 19.4 (95% CI: 16.4, 22.9). Incidence was highest in those with mixed-age partnerships: 28.5 (95% CI: 21.8, 37.1) and those whose partners were all <30 (23.9; 95% CI: 18.8, 30.4), and lowest if partners were ≥30 (7.5; 95% CI: 4.8, 11.8). In a multivariable analyses adjusting for age, sex (of index), injection frequency, and injection partnership 'monogamy', we found evidence for an interaction: the highest HCV incidence was seen in PWID whose partners were all <30 and who knew at least one of their partners was HCV-positive (58.9, 95% CI: 43.3, 80.0; p<0.01).

CONCLUSIONS

Younger injectors are more likely to acquire HCV from their similarly-aged peers, than older injecting partners. Protective seroadaptive behavior may contribute to reduce incidence. These findings can inform new HCV prevention approaches for young PWID needed to curb the HCV epidemic.

Elimination of hepatitis C virus infection among people who use drugs: Ensuring equitable access to prevention, treatment, and care for all

There have been major strides towards the World Health Organization goal to eliminate hepatitis C virus (HCV) infection as a global public health threat. The availability of simple, well-tolerated direct-acting antiviral therapies for HCV infection that can achieve a cure in >95% of people has provided an important tool to help achieve the global elimination targets. Encouragingly, therapy is highly effective among people receiving opioid agonist therapy and people who have recently injected drugs. Moving forward, major challenges include ensuring that new infections are prevented from occurring and that people who are living with HCV are tested, linked to care, treated, receive appropriate follow-up, and have equitable access to care. This editorial highlights key themes and articles in a special issue focusing on the elimination of HCV among people who inject drugs. An overarching consideration flowing from this work is how to ensure equitable access to HCV treatment and care for all. This special issue maps the field in relation to: HCV prevention; the cascade of HCV care; strategies to enhance testing, linkage to care, and treatment uptake; and HCV treatment and reinfection. In addition, papers draw attention to the 'risk environments' and socio-ecological determinants of HCV acquisition, barriers to HCV care, the importance of messaging around the side-effects of new direct-acting antiviral therapies, the positive transformative potential of treatment and cure, and the key role of community-based drug user organizations in the HCV response. While this special issue highlights some successful efforts towards HCV elimination among people who inject drugs, it also highlights the relative lack of attention to settings in which resources enabling elimination are scarce, and where elimination hopes and potentials are less clear, such as in many low and middle income countries. Strengthening capacity in areas of the world where resources are more limited will be a critical step towards ensuring equity for all so that global HCV elimination among PWID can be achieved.