Risk factors

Sharing needles

Individuals who have shared needles and syringes to inject illegal drugs have the highest risk of HCV infection of any group. HCV viral infectivity can persist for days or longer given favorable conditions. HCV is efficiently transmitted via contaminated dried blood on injection paraphernalia including shared needles, syringes, cookers and filters (e.g., cotton or a cigarette filter used to strain particulates from a drug solution); even longer under favorably moist conditions, like the barrel of a syringe.

Some studies also link HCV infection with the sharing of straws to snort cocaine. Apparently blood to blood transfer can occur when a soda straw is shared to "sniff" illegal drugs. Past or current users of illegal drugs should be evaluated carefully, and when necessary, referred to drug treatment programs prior to antiviral therapy.

Received clotting factor concentrate produced before 1987.
People who received clotting factor concentrates prepared from pooled plasma, before 1987, are at risk for HCV and chronic liver disease. They are also at risk for co-infection with HIV. Studies have demonstrated that 87% of hemophiliacs contracted HCV from blood products before 1987. Many were co-infected with HIV. The HIV co-infection often resulted in more severe symptoms and rapid progression of the HCV related symptoms.

Today blood donors are screened for risk factors and their blood is tested for evidence of current or previous bloodborne disease. Blood which tests positive for exposure to bloodborne disease is excluded. Blood products, such as clotting factors VIII and IX, have been treated to inactivate undetected encapsulated viruses such as HIV-1, HBV and HCV since 1987. The inactivation methods include prolonged exposure to heat (pasteurization), and a solvent/detergent process which disrupts the viral coat. However, there is some evidence that HCV may be more or less resistant to some of these processes.

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Long-term hemodialysis
The CDC has conducted surveillance of hemodialysis-associated hepatitis since the early 1970's. In 2001, routine testing of hemodialysis patients for HCV on admission was recommended, but not required. In the 2002 report, 63% of centers were following the recommendation. Of those, 11.5% reported that at least one patient converted from negative to positive during 2002. The overall prevalence of HCV in those tested was 7.8%, a considerably higher rate than the general population, but the rate had decreased from 25.7% in 1995. However, the HCV rate from chronic hemodialysis patients in the general population is about 10%. There was no difference in HCV incidence in centers that reused dialyzers as opposed to those that used disposable dialyzers. The report stated that HCV transmission has occurred in facilities where there were multiple opportunities for cross-contamination among patients, including failure to clean and disinfect contaminated equipment, supplies, and environmental surfaces that were shared between patients.

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Transfusion of blood or blood components or a solid organ transplant before 1992

Before 1989, transfusion with blood or blood components was the primary cause of blood-borne infection. The first blood test for HCV became available in May of 1990. An improved test was put into use in 1992. Since then all donated blood has been screened for hepatitis C, and this mode of transmission has virtually disappeared in the United States. However, 4 in 1 million people, who voluntarily donate blood, carry HCV RNA without generating detectable antibody blood levels, so there is still a small possibility that a recipient of blood or blood components could become infected with HCV.

While the guidelines suggest that transplants after 1992 are safe, that has not been the case. In 2000, an organ donor who tested negative for hepatitis C using the standard blood tests of the time, transmitted the virus through organ and tissue transplants to a number of recipients. Three of 6 organ recipients died of hepatitis C and 5 of 32 tissue recipients became infected. According to the CDC, the donor was asymptomatic and had no history that put the donor at high risk for infection. It was likely that the donor was recently infected and not yet generating detectable antibodies. While RNA tests are more accurate than antibody screens, not all health facilities have easy access to RNA testing and delays in getting results could jeopardize the viability of the tissue and success of the transplant. Therefore, requiring RNA testing of all donors poses problems. The number of infected individuals is likely quite small, but not insignificant.

In 2003, a study reported that about 300 musculoskeletal tissue specimens infected with hepatitis C were distributed by US tissue procurement centers each year. The problem was that the FDA had no approved test to detect the presence of HCV in cadaver donor tissues. About 18,000 cadavers provide 650,000 allografts for transplantation, such as the cartilage for joint surgeries.

Tissues from one infected donor could be distributed among dozens of recipients, resulting in multiple infections in recipients and those who have contact with them. In June 2004, the FDA approved the first nucleic acid test (NAT) for cadaver specimens, but did not require at that time that tissue banks use the test. However, in response to concerns about the safety of cadaver donor tissue, in August 2004, the American Association of Tissue Banks (AATB) required its accredited facilities to implement nucleic acid testing for both HIV-1 and HCV. Therefore, banks accredited by AATB began testing immediately. Nationwide testing was not required until March 2005, so further infected tissue may have been distributed.

Percutaneous or permucosal occupational exposure to HCV-positive blood

There is very little difference in the rates of hepatitis C among health care workers (2%) than in the general population. However, the prevalence of HCV in hospitalized patients could be as high as 18%, so there is always the danger of exposure to blood, especially through needlesticks. The risk of becoming infected after a needlestick injury involving HCV positive blood ranges from 0% to 10%. The general rule followed for risk related to needle-stick is called the Rule of 3's: HBV is transmitted in 30% of exposures, HCV in 3%, and HIV in 0.3%. Because there is no approved prophylactic treatment for hepatitis C, only treatment for active disease, a health care or other worker who is exposed to HCV infected blood should receive follow-up testing for 6 to 9 months to determine if infection occurred.

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Health care workers have much higher rates of HCV than the general population.

Born to a HCV positive women

The lowest rates of complications have been reported in those who developed HCV as children. However, long term follow-up studies will eventually provide more information about lifetime effects. About 5% of children born to infected mothers contract HCV. The rate is higher, 14%, for children whose mothers are co-infected with HIV and HCV. Neither pregnancy nor breast-feeding is contraindicated for women with HCV who are not currently receiving anti-viral treatment.

Sexual transmission

The risk for transmitting HCV from sexual exposure tends to be lower than for HIV transmission, with only about 15% of cases of hepatitis C related to sexual intercourse. However, a substantial portion of the adult population in the United States has had unprotected sex with multiple partners and, because of the large number of people infected with HCV, some of these contacts are with infected individuals. Studies of long-term spouses of HCV infected partners found infection rates of 0% to 4%. Additional studies found that males with an HCV-infected female partner had rates no higher than those with a non-infected partner. However, female patients with an HCV-infected partner were almost 4 times as likely to develop HCV than females with a negative partner. This suggests that transmission from male to female is more efficient than from female to male. The HCV rates for males having sex with males (MSM) is similar to heterosexual rates.

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Sharing personal items such as razor or toothbrushes

There is very little danger involved in sharing living space with someone infected with HCV, other than through sexual transmission. However, it is possible to become infected by coming into contact with blood contaminated items, such as razors and toothbrushes.

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