Globally, more than 2.3 million people are infected with both HIV and hepatitis C (HCV) viruses, revealed a new study.
Of these, more than half, or 1.3 million, are people who inject drugs (PWID) -- HIV infections caused by injecting drugs.
"The study shows that not only are people with HIV at much higher risk of HCV infection, groups such as people who inject drugs have an extremely high prevalence of HCV infection - over 80 percent," said Philippa Easterbrook, from World Health Organization's Global Hepatitis Program.
Globally, there are 37 million people infected with HIV and around 115 million people with chronic HCV infection.
"Improvement in the surveillance of HCV and HIV is imperative to help define the epidemiology of co-infection and inform appropriate policies for testing, prevention, care and treatment to those in need," said lead author Lucy Platt, senior lecturer at the University of London.
The study shows the need to scale up prevention interventions, such as needle and syringe programs and opioid substitution therapy, as well as access to HIV and HCV treatment, to reduce morbidity and new infections, the researchers suggested.
The study, published online in The Lancet Infectious Diseases, systematically reviewed 783 medical studies from worldwide sources to build the first global estimates on the prevalence of HIV/HCV co-infection (measured by HCV antibody) as a public health problem.
The researchers included studies with estimates of HCV co-infection in the main HIV population, as well as sub-groups of PWID, homosexuals, pregnant women and the general population.