Around one in two people who inject drugs (PWID) have been exposed to hepatitis C virus (HCV) and potentially 6 million PWID globally are chronically infected.
We know that PWID who have been injecting for longer, who have recently been to prison, who share needles and who have HIV are all more likely to be exposed to HCV. However, these results have largely been driven by available data in high-income countries.
Less is understood about how national-level factors may be associated with HCV among PWID in that country. Certain structural barriers, like income level, can influence the accessibility of harm reduction services that try and reduce the transmission of blood-borne viruses, and ecological factors like HCV prevalence in the general population or incarceration rates, which may increase the likelihood of exposure to the virus.
Our recent systematic review of 223 studies set in 84 different countries, looked at the evidence around HCV antibody (anti-HCV) among PWID and determined whether certain socio-demographic and ecological factors were associated with anti-HCV prevalence across countries.
Where there was more HIV, there was more anti-HCV
Samples with more people testing positive for HIV had more people testing positively for anti-HCV. Although we could not determine whether these were the same people (i.e. individuals with anti-HCV also having HIV), this is consistent with what we know about the relationship between these blood-borne viruses.
HCV and HIV have the same risk factors for transmission. Among PWID, that includes sharing injecting equipment and having sex without a condom. Because people with HIV have a lower immune system, they may also be more vulnerable to contracting HCV virus. HIV-HCV co-infection is significant as the prognosis for chronic liver, kidney or cardiovascular diseases are much worse when this co-infection is left untreated.
Among PWID in countries with a higher human development index score, anti-HCV prevalence was higher
The human development index score incorporates information on life expectancy, education, and income (per capita) of a country. We found that PWID in developed countries are more exposed to HCV than PWID in developing countries. However, HCV is higher among the general population in developing compared to developed countries. These different patterns are important for a few reasons:
- It seems that in parts of the world where injecting drug use is a relatively new phenomenon there is less HCV.
- There is an opportunity to prevent widespread HCV among PWID in developing countries with the right interventions.
- Although there are quite large populations of PWID infected with HCV in developed countries, scaling up testing, treatment and education about HCV transmission is achievable and highly necessary if we want to eliminate HCV.
This study is one small piece to better understanding a large and complex problem. These results are informed from data from only 84 countries, which is just under half of all countries where we know there is injecting occurring. If we want to eliminate HCV, we need a better understanding in those countries with no available data.