Hepatitis C Transmission

Hepatitis C (HCV) is passed when infected blood gets into the bloodstream of someone who doesn’t have HCV. Injection drug use is a common way of getting HCV. Blood transfusions and organ transplantation prior to July 1992 were other common ways to become infected with HCV. Accurate screening for HCV has made blood transfusions and transplants much safer. Today, HCV is rarely transmitted via donated blood, tissue, or organs. 1,2

Injection drug use

People who inject drugs have a high risk of getting HCV by sharing needles, syringes, and anything used in the process of preparing and injecting drugs. The virus is passed along very efficiently from infected equipment to a non-infected individual. Anything that comes in contact with the virus is potentially infectious, including syringes, cookers, cotton filters, preparation water, the surface on which the drug is prepared, and the drug itself. In fact, HCV can survive up to 63 days in a syringe and, at room temperature, the virus can remain infectious for up to 6 weeks. 3,4 Sharing needles, syringes, and other equipment used in injecting drugs accounts for over 60% of new cases of HCV.1 In one recent study, up to 77% of injection drug users tested positive for the HCV.5

Blood transfusion

Before an accurate HCV screening test was introduced in July 1992, blood transfusions were a common way to become infected with HCV. People with diseases requiring multiple transfusions, such as thalassemia or hemophilia, were at particularly high risk for contracting HCV infection. However, now it is rare to become infected with HCV due to a blood transfusion.1 The risk of getting HCV infection from a blood transfusion is estimated at 1 in 2 million per unit of transfused blood. 6

Healthcare workers

One US study found that exposures involving needlestick or other injuries occurred most often in the operating room, in patient rooms, and in the emergency department. The most common devices associated with exposures were disposable syringes and suture needles. Exposures were most common among nurses, followed by physicians (residents and attending physicians), surgery attendants, phlebotomists, and laboratory technicians. The factors that increased risk of exposures among healthcare workers included long work hours and sleep deprivation, especially among medical trainees. 2

Healthcare (medical and dental) exposure

Outbreaks of HCV infection have occurred in hospitals and other healthcare settings primarily because of unsafe injection practices.1 Several studies conducted in Europe have shown that risk for HCV transmission is increased during hospitalization, particularly in people who undergo surgery, who are admitted to an emergency department, or who undergo diagnostic or therapeutic procedures where there is risk of exposure to blood.7 Additionally, in the US, HCV exposures have been reported in the dental health setting.8

Organ transplantation

Organ transplantation is largely safe since the development of accurate HCV screening tests in 1992. Before screening tests were instituted, the risk of contracting HCV during organ transplantation was high. The risk of getting HCV from an organ transplant where the donor is HCV-infected still remains high. However, when HCV RNA testing of donors and organs is done, as recommended by the US Public Health Service, the risk of contracting HCV is quite low.9

Household contact

Studies have shown that transmission of HCV through casual contact with an infected person or sharing personal hygiene items (such as a toothbrush or razor) with an infected person is possible. However, the risk is generally considered low. HCV is not passed casually, such as by kissing, hugging, or sharing eating utensils.1

Sexual contact

The risk of HCV transmission through sexual contact is generally low, especially for HIV-negative individuals.10 HCV sexual transmission is 0% to 0.6% per year for those in monogamous heterosexual relationships, and 1% per year for those with multiple sexual partners.11 There are no reports of female-to-female sexual transmission of HCV. There may be a slight risk of HCV transmission during menses, and common sense suggests using barrier protection during this time.1

HCV sexual transmission risk increases among those who are HIV-positive, particularly among HIV-positive men who have sex with men.10 HCV risk increases in HIV-infected men with decreased CD4+ T cell counts, particularly counts of 500 or below. Certain sexual practices seem to increase risk for infection. These include unprotected receptive anal sex with multiple partners. The use of drugs and alcohol during sex is associated with increased risk for HCV transmission.12

Perinatal transmission

Vertical transmission is the term used when HCV is passed from an HCV-positive woman to her child during pregnancy, childbirth, or in the month following birth. Mother-to-child HCV transmission occurs about 5% of the time. Vertical transmission risk doubles if a woman is also infected with HIV. There are no recommendations for steps that pregnant women may take to reduce the risk for HCV transmission. The choice of whether to deliver vaginally or by Cesarean should not be made based on HCV infection. There is no evidence that HCV can be passed to an infant via breastfeeding.1 Common sense suggests that women refrain from breastfeeding with a nipple that is bleeding.

Hemodialysis

The risk for becoming infected with HCV during dialysis has decreased steadily over the past three decades. However, the possibility of HCV transmission via hemodialysis remains, even though the risk is low. There is ongoing debate concerning how to reduce risk of transmission in this setting, including routine testing for HCV antibodies, isolation of HCV positive patients, or use of dedicated dialysis machines for positive patients. At present, the US Centers for Disease Control and Prevention (CDC) do not recommend any of these steps. However, the CDC does recommend strict adherence to general precautions, including careful attention to hygiene and sterilization of dialysis machines.1,13,14

Other modes of transmission

There may be other ways that HCV can be transmitted, including practices involved in traditional folk medicine (e.g., scarification), tattooing, body piercing, commercial barbering, and the beauty industry (e.g., nail salons). There is no evidence to determine the precise transmission risk for these practices, but the risk is probably low. The CDC has determined that tattooing or piercing done at a licensed, regulated business where infection control practices are followed, poses little risk for transmission of HCV. However, in unregulated settings where there are limited infection-control practices (e.g., use of non-sterile needles or other instruments), such as in prison or in an unlicensed business, the risk of contracting HCV and other infectious diseases increases substantially.14

Written by: Jonathan Simmons | Last reviewed: March 2015.
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