 | Hepatitis C Virus Transmission | |
 | | Introduction | |
Some modes of transmission of hepatitis C virus are well documented and widely accepted; others are less well defined and require further study. It is clear that HCV is most frequently transmitted through large or repeated direct percutaneous exposures to infected blood. The two most common exposures associated with transmission of HCV are blood transfusion and injection drug use.
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| Blood Transfusion/Receipt of Blood Products | |
Early case-control studies of patients with newly acquired, symptomatic non-A, non-B hepatitis found a significant association between disease acquisition and a history six months prior to illness of blood transfusions, injection drug use, health care employment with frequent exposure to blood, personal contact with others who had hepatitis, multiple sexual partners or low socioeconomic
status.(1,2) Today, HCV is rarely transmitted by blood transfusion or transplantation of organs due to thorough screening of the blood supply for the presence of the virus and inactivation procedures that destroy bloodborne viruses. In the last several years, blood banks have instituted techniques that utilize nucleic acid amplification of the hepatitis C virus, which will detect the presence of virus even in newly-infected patients who are still hepatitis C antibody-negative. These techniques are estimated to have prevented 56 transfusion-associated HCV infections per year in the U.S. since 1999, and have lowered the current risk of acquiring HCV via transfused blood products to 1 in 2
million.(3)
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| Injection Drug Use | |
Injection drug use has been the principal mode of transmission of HCV since the 1970's. In comparison to other viral infections, HCV is more rapidly acquired after initiation of intravenous drug
use.(4) In addition, rates of HCV among young injecting drug-users are four times higher than HIV
infection.(5) Studies of injection drug users have demonstrated that the prevalence of HCV infection in them is extremely high, with up to 90% having been
exposed.(6) In addition, the incidence of new infections is also high, with seroconversion rates of 10-20 percent per year of
injecting.(7,8) Duration of injecting is the strongest single predictor of risk of HCV infection among injection drug
users.(9)
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| Sexual Transmission | |
Sexual transmission of HCV has been controversial. It is believed that HCV can be transmitted sexually, but that such transmission is inefficient. The likelihood of HCV infection increases with the number of lifetime sexual partners. A history of a sexually transmitted disease, sex with a prostitute, more than five sexual partners per year, or a combination of these has been independently associated with positive HCV
serology.(10) Distinction appears to exist between the specific sexual behaviors listed above, and stable, monogamous sexual activity, which is rarely associated with HCV transmission. The frequency of HCV transmission between monogamous sexual partners is very low according to most
studies.(11,12)
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| Other Modes of Transmission | | | Household Transmission | |
The prevalence of HCV among household contacts of people with HCV infection is low. Moreover, the study of HCV transmission among household contacts is complicated by the difficulty in ruling out other possible modes of acquisition. Many of the studies include a small number of nonsexual contacts, and often include children born to mothers with HCV
infection.(13) Therefore, it is difficult to determine whether nonsexual, non-blood contact is a route of transmission for HCV.
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| Occupational Exposures | |
Health care workers who have exposure to blood are at risk of infection with HCV and other bloodborne pathogens. The prevalence of HCV infection, however, is no greater in health care workers, including surgeons, than for the general population. According to the CDC, the average rate of anti-HCV seroconversion after unintentional needlesticks or sharps exposure from an HCV-positive source is 1.8% (range 0%-7%). An Italian study of 4,403 needlesticks among healthcare workers found 14 seroconversions
(0.31%).(14) There is an emerging body of literature, however, that close follow-up of health care workers after a needlestick from a patient with chronic HCV, with early interferon and ribavirin therapy for the healthcare worker if they develop HCV viremia but fail to clear within 3-6 months, can be a beneficial management
strategy.(15)
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| No Identifiable Source of Infection | |
According to the Centers for Disease Control and Prevention, injection drug use accounts for approximately 60% of all HCV infections in the United States, while other known exposures account for
20-30%.(5) Approximately 10% of patients in most epidemiological studies, however, have no identifiable source of
infection.(16) HCV exposure in these patients may be from a number of uncommon modes of transmission, including vertical transmission, and parenteral transmission from medical or dental procedures prior to the availability of HCV testing. There are no conclusive data to show that persons with a history of exposures such as intranasal cocaine use, tattooing or body piercing are at an increased risk for HCV infection based on these exposures solely. It is believed, however, that these are potential modes of HCV acquisition in the absence of adequate sterilization techniques.
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| References | | Alter MJ, et al. Sporadic non-A, non-B hepatitis: frequency and epidemiology in an urban United States population. J Infect Dis 1982;145:886-893.
Alter MJ, et al. Importance of heterosexual activity in the transmission of hepatitis B and non-A, non-B hepatitis. JAMA 1989;262:1201-1205.
Stramer SL, et al. Detection of HIV-1 and HCV infections among antibody-negative blood donors by nucleic acid-amplification testing. N Engl J Med 2004;351:760-768.
Garfein RS, et al. Viral infections in short-term injection drug users: the prevalence of the hepatitis C, hepatitis B, human immunodeficiency, and human T-lymphotropic viruses.. Am J Public Health 1996; 86:655-671.
Centers for Disease Control and Prevention. Recommendations for prevention and control of hepatitis C virus (HCV) infection and HCV-related chronic disease. MMWR 1998;47(RR-19):1-39.
Patrick DM et al. Public health and hepatitis C. Can J Public Health 2000;91(suppl 1):S18-S23.
Hahn JA, et al. Hepatitis C virus infection and needle exchange use among young injection drug users in San Francisco. Hepatology 2001;34:180-187.
Thorpe LE, et al. Risk of hepatitis C virus infection among young injection drug users who share injection equipment. . Am J Epidemiol 2002;155:645-653.
Conry-Cantilena C, et al. Routes of infection, viremia, and liver disease in blood donors found to have hepatitis C virus infection.. N Engl J Med 1996;334:1691-6.
Gross JB. Hepatitis C: A sexually transmitted disease?Am J Gastroenterol 2001;96:3051-3053.
Vandelli C, Renzo F, Romano L, Tisminetzky S, De Palma M, et al. Lack of evidence of sexual transmission of hepatitis C among monogamous couples: results of a 10-year prospective follow-up study.. Am J Gastroenterol 2004;99:855-859.
Terrault NA.Sexual activity as a risk factor for hepatitis C. Hepatol 2002;36:S99-105.
Ackerman Z, Ackerman E, Paltiel O.Intrafamilial transmission of hepatitis C virus: a systematic review. J Viral Hepatitis 2000;7:93-103.
De Carli G, Puro V, Ippolito G, et al. Risk of hepatitis C virus transmission following percutaneous exposure in healthcare workers.. Infection 2003;31-suppl 2:22-27.
Sulkowski MS, Ray SC, Thomas DL. Needlestick transmission of hepatitis C. JAMA 2002;287:2406-2413.
Flamm SL, Parker RA, Chopra S. Risk factors associated with chronic hepatitis C virus infection: limited frequency of an unidentified source of transmission. Am J Gastroenterol 1998;93:597-600.
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