Scotomas in molecular virology and epidemiology of hepatitis C virus

Table 4 Epidemiological features of hepatitis C virus infection

Epidemiological index	Current consensus
Source of infection	Chronic HCV carriers
Route of transmission	HCV transmission occurs primarily through exposure to infected blood. Past: Receiving infected blood or organ transplantation, from accidental exposure to infected blood, and sexual transmission in persons with high risk behaviours. Present: HCV is usually spread by sharing infected needles with a chronic HCV carrier, and some people acquire the infection through nonparenteral means that have not been fully defined.
Susceptible population	General population
Incubation period	Average 6-10 wk
Prevalence and incidence	3% of the world’s population have HCV
Rate of chronic infection	Up to more than 80%
Outcome of chronic infection	10%-20% of chronic HCV carriers may develop into cirrhosis and liver failure. 1%-5% of chronic HCV carriers are associated with the development of hepatocellular carcinoma
Molecular epidemiology	HCV is classified into eleven major genotypes (designated as 1-11), many subtypes (designated a, b, c, etc.), and about 100 different strains (numbered 1, 2, 3, etc.) based on the genomic sequence heterogeneity. Genotypes 1-3 have a worldwide distribution. Types 1a and 1b are the most common, accounting for about 60% of global infections. Type 2 is less frequently represented than type 1. Type 3 is endemic in southeast Asia and is variably distributed in different countries. Genotype 4 is principally found in the Middle East, Egypt, and central Africa. Type 5 is almost exclusively found in South Africa, and genotypes 6-11 are distributed in Asia.
Stability	HCV is inactivated by exposure to lipid solvents or detergents, heating at 60 °C for 10 h or 100 °C for 2 min in aqueous solution, formaldehyde (1:2000) at 37 °C for 72 h, β-propriolactone and UV irradiation.
Vaccine	Not available

HCV: Hepatitis C virus.