- HCV can be passed to others through blood and bodily fluids such as vaginal secretions and semen. It is commonly spread through blood transfusions, in which blood is transferred from one person to another, or by sharing needles contaminated with the virus, particularly among street drug and steroid users. It is advisable to check for HCV in people who received a blood transfusion or organ transplant before 1992, when there were no tests to identify the virus. The infection cannot spread by hugging, kissing, or shaking hands with an infected person.
- Equipment used for procedures such as tattooing, body piercing, and acupuncture may transmit HCV infection. In rare cases, transmission may occur through contaminated (infected) dialysis equipment. Dialysis is a procedure used to filter harmful wastes from blood in people with impaired kidney function. The virus may also be transmitted from infected mothers to their infants, although this is uncommon.
HCV rapidly replicates, or produces multiple copies of itself, with nearly 1 trillion particles produced every day in an infected individual. Its high mutation rate helps the virus elude the host's immune response. A mutation is a change within a gene, specifically a change in the sequence of base pairs in the DNA that make up a gene. Several studies indicate that HCV replicates within liver cells. Circulating HCV particles enter the liver cells by initially binding to specific surface receptors. These receptors are protein molecules to which the viral particle attaches itself to gain entry into the cell. Because of the high mutation rate of the HCV, the liver cell perceives the mutated or genetically altered viral RNA as its own RNA and proceeds to replicate it. Because the viral RNA is assumed to be the body's own RNA, there is no immune response generated. Thus, the viral RNA is successful in avoiding attack by the host's immune system.