Epidemiological studies on viral infections and co-infections: Human immunodeficiency virus, hepatitis C virus and human papillomavirus

The research described in this thesis aimed to increase our understanding of the incidence, disease progression and treatment of human immunodeficiency virus (HIV), hepatitis C virus (HCV), and human papillomavirus (HPV) infections and co-infections in key populations. Chapter 1 contains an overview of these viral epidemics, a section highlighting the value of observational cohort studies as used throughout this thesis, and some of major historical events related to these epidemics: starting with the heroine-use epidemic in the 1970s and HIV epidemic in the 1980s, which gave rise to the Amsterdam Cohort Studies (ACS), up until the availability of a vaccine against HPV infection and novel treatments for HCV. In chapter 2 of this thesis we show that HCV continues to spread among HIV-positive MSM and that HCV has a temporary, negative effect on the immune system. We also show that HIV increases the risk of HPV acquisition and persistence, both being important factors for anal cancer development. Chapter 3 covers studies among people who use drugs in Amsterdam. This group transitioned from high HIV and HCV incidence during the 1980s, to high HIV- and drug-related excess mortality during the 1990s, to a lower excess mortality in the last decade, although the burden of liver disease is now high. Additionally, we show that novel HCV treatment is highly cost-effective in this group, but the uptake of this treatment was low in 2015. Lastly, in chapter 4, the relevance of these studies is discussed together with recommendations for future research, prevention and care strategies