Social networks shape the transmission dynamics of hepatitis C virus

• Published in: PloS one 2010-06, Vol.5 (6), p.e11170-e11170
• Main Authors: Romano, Camila Malta, de Carvalho-Mello, Isabel M V Guedes, Jamal, Leda F, de Melo, Fernando Lucas, Iamarino, Atila, Motoki, Marco, Pinho, João Renato Rebello, Holmes, Edward C, de Andrade Zanotto, Paolo Marinho
• Format: Article
• Language: English
• Subjects: Age; Archives & records; Bioinformatics; Blood; Blood & organ donations; Blood banks; Blood transfusion; Blood transfusions; Cirrhosis; Consortia; Disease; Disease susceptibility; Disease transmission; Drug abuse; Epidemics; Epidemiology; Evolutionary Biology/Microbial Evolution and Genomics; Gastroenterology; Gene sequencing; Genotypes; Health risks; Hepatitis; Hepatitis C; Hepatitis C - classification; Hepatitis C - transmission; Hepatitis C virus; Hepatology; Humans; Infections; Infectious Diseases/Viral Infections; Laboratories; Liver; Liver cancer; Liver cirrhosis; Liver diseases; Medicine; Pandemics; Pediatrics; Phylogenetics; Phylogeny; Population; Public health; Public Health and Epidemiology/Infectious Diseases; Public Health and Epidemiology/Social and Behavioral Determinants of Health; Risk; Risk groups; Risk taking; Sexual transmission; Social aspects; Social factors; Social networks; Social organization; Social Support; Substance abuse treatment; Transfusion; Vaccines; Viruses
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0011170

Hepatitis C virus (HCV) infects 170 million people worldwide, and is a major public health problem in Brazil, where over 1% of the population may be infected and where multiple viral genotypes co-circulate. Chronically infected individuals are both the source of transmission to others and are at risk for HCV-related diseases, such as liver cancer and cirrhosis. Before the adoption of anti-HCV control measures in blood banks, this virus was mainly transmitted via blood transfusion. Today, needle sharing among injecting drug users is the most common form of HCV transmission. Of particular importance is that HCV prevalence is growing in non-risk groups. Since there is no vaccine against HCV, it is important to determine the factors that control viral transmission in order to develop more efficient control measures. However, despite the health costs associated with HCV, the factors that determine the spread of virus at the epidemiological scale are often poorly understood. Here, we sequenced partial NS5b gene sequences sampled from blood samples collected from 591 patients in São Paulo state, Brazil. We show that different viral genotypes entered São Paulo at different times, grew at different rates, and are associated with different age groups and risk behaviors. In particular, subtype 1b is older and grew more slowly than subtypes 1a and 3a, and is associated with multiple age classes. In contrast, subtypes 1a and 3b are associated with younger people infected more recently, possibly with higher rates of sexual transmission. The transmission dynamics of HCV in São Paulo therefore vary by subtype and are determined by a combination of age, risk exposure and underlying social network. We conclude that social factors may play a key role in determining the rate and pattern of HCV spread, and should influence future intervention policies.