Transmission of Hepatitis C
Hepatitis C is believed to be transmitted only by blood. However, unlike many other blood borne viruses (like HIV) virtually any source of blood or blood products seems to be capable of carrying the virus, even if the source is indirect - like a used razor, for example. This makes hepatitis C far more transmissible than most other blood borne viruses - including HIV.
Many hepatitis C victims contracted the disease through blood transfusions in the 1970s and 1980s. Rates of post-transfusion hepatitis during this period were determined to have been between 8% and 10%. Effective bloodscreening for the virus was developed and implemented by 1990, which lowered the rates of post-transfusion hepatitis to less than 5% from 1990-1993. Since then, improved testing has led to drastic reductions in risk, down to less than 1% after 1993. However, anyone who had a blood transfusion prior to that time is at risk for having been infected. Incidence of hepatitis C infection among hemophiliacs remained high through 1993, because plasma used to treat hemophilia is often a mixture from many different donors. However, incidence of new infection among hemophiliacs has rapidly approached zero as better methods have been employed.
Tattooing, as well as many body piercing practices, such as acupuncture and ear-piercing, have contributed significantly to the spread of HCV, even in industrial nations. Needle-stick injuries, contaminated medical equipment, and blood spills in health care
settings are also responsible for many cases of HCV.
The most significant risk behavior for HCV infection is drug use, particularly I.V. drug use, and is responsible for about 30-40% of all identified cases of hepatitis C. As with HIV, the sharing of contaminated needles and other drug paraphernalia increases the chance of infection dramatically. Incidence of infection among I. V. drug users has surpassed 50 percent in many studies, and reached 100 percent in others. Cocaine users have also been shown to transmit the virus by sharing snorting straws.
Heterosexual or homosexual activity with multiple sexual partners has been clearly identified as a mode of transmission, but the exact risk is unknown. Because of the lack of
sufficient information, persons in long-term, monogamous relationships are not advised to change sexual practices. Day-to-day contact with another household member that has hepatitis C has also been strongly implicated. Maternal-infant transmission has also been documented as a mode of spread.
Certain specialized risks have also been identified - such as manicures, shared toothbrushes, or straight razors in barber shops.
In more than 40% of all cases, the infected individuals cannot identify a source for their infection. It is believed that most of these are due to known risk factors - however, in more than 10% of all cases, no risk factor can be identified. There are clearly other, as yet unidentified modes of transmission.