Miriam J. Alter, PhD

NIH Consensus Development Conference on
Management of Hepatitis C: 2002 

Bethesda, Maryland

June 10-12, 2002

Historically, the most reliable data on risk factors associated with acquiring hepatitis C virus (HCV) infection have been obtained from cohort (prospective) studies that determined the risk of developing acute infection after a specific exposure and case-control (retrospective) studies that determined if a history of exposure before onset of disease was associated with newly acquired (acute) hepatitis C. Risk factors identified by these studies in the United States included injecting drug use, blood transfusion and solid organ transplants from infected donors, occupational exposure to blood (primarily contaminated needle sticks), birth to an infected mother, sex with an infected partner, or multiple heterosexual partners.

The major limitation of such studies is that they are unlikely to identify associations with exposures that result only rarely in infections. For example, results of case-control studies have indicated no association between acquiring hepatitis C and exposures resulting from medical, surgical, or dental procedures. However, outbreaks of HCV infection have been associated with contaminated equipment in hemodialysis settings and unsafe injection practices in both inpatient and outpatient settings. Most of these outbreaks have involved patient-to-patient transmission.

Only two instances of transmission have been reported from HCV-infected health care workers to patients in the United States. Neither of these was associated with the performance of exposure-prone invasive procedures, but rather with contamination of patients’ narcotics used for self-injection.

The contribution of these various risk factors to the overall burden of HCV infections is influenced both by their efficiency in transmitting HCV and by the frequency of the exposure in the population. In the United States, the relative importance of the two most efficient exposures associated with transmission of HCV, blood transfusion and injecting drug use, has changed over time. Blood transfusion, which accounted for a substantial proportion of HCV infections acquired >15–20 years ago, rarely accounts for recently acquired infections. In contrast, injecting drug use consistently has accounted for a substantial proportion of HCV infections and currently accounts for 60 percent of HCV transmission. The relative importance of other exposures has changed little over time.

Unprotected sex with an infected partner or with multiple partners has accounted for an estimated 15 percent of HCV infections. Although the role of sexual activity in the transmission of HCV remains controversial, and the virus is inefficiently spread in this manner, the relatively substantial contribution of sexual exposures to the burden of disease can be explained by the fact that sexual activity with multiple partners is a common behavior in the population and that the large number of chronically infected persons provides multiple opportunities for exposure. In contrast to sexual exposures, occupational and perinatal exposures contribute to a small proportion overall of infections, and together with nosocomial or iatrogenic exposures, they account for about 5 percent of HCV infections. HCV is not transmitted efficiently through occupational exposure. The prevalence of HCV infection among health care or public safety workers averages 1–3 percent and has not been affected by changes or improvements in barrier precautions. Transmission rates from HCV infected mothers to their infants average 5 percent or less, no associations have been demonstrated with mode of delivery or type of feeding, and infants who acquire HCV infection at birth may be less likely to develop chronic infection. Thus, about 90 percent of HCV infections can be accounted for by known percutaneous or mucosal exposures to blood. In the remaining 10 percent, no recognized source for infection can be identified. Numerous studies have attempted to identify additional risk factors for HCV infection. While case-control studies of acute hepatitis C reported no association with tattooing, acupuncture, ear piercing, military service, or foreign travel, cross-sectional and prevalence studies of volunteer blood donors, disease-specific clinic patients, and veterans receiving care in VA hospitals have yielded conflicting results for some of these risk factors. The lack of consistency among studies of highly selected groups for which the temporal sequence of exposure relative to the disease was unknown is cause for concern about the generalizability of such results.

Strategies for reducing or eliminating the potential risk for transmission include: (1) screening and testing of donors; (2) virus inactivation of plasma-derived products; (3) risk reduction counseling and services; and (4) implementation and maintenance of infection-control practices. Strategies for reducing risks for chronic disease include: (1) identification, counseling, and testing of at-risk persons; and (2) medical evaluation and management of infected persons.

Health care professionals in all patient care settings routinely should obtain a history that inquires about blood transfusion, use of illegal drugs (injection and non-injection) and evidence of high-risk sexual practices, such as multiple sex partners or history of STDs. Primary prevention of illegal drug injecting will eliminate the greatest risk factor for HCV infection in the United States. Although consistent data are lacking regarding the extent to which sexual activity contributes to HCV transmission, persons having multiple sex partners are at risk of STDs such as HIV, HBV, syphilis, gonorrhea, and chlamydia.

Testing should be offered routinely to persons most likely to be infected with HCV, which include persons who ever injected illegal drugs; received plasma-derived products known to transmit HCV infection that were not treated to inactivate viruses; received transfusions or solid organ transplants before July 1992; and were long-term hemodialysis patients. Based on a recognized exposure, testing also is indicated for health-care workers after needle sticks, sharps, or mucosal exposures to HCV-positive blood and for children born to HCV-positive women.

Immune globulin and antiviral agents are not recommended for postexposure prophylaxis of hepatitis C.HCV-positive persons with a long-term steady partner do not need to change their sexual practices; however, they should discuss with their partner the need for counseling and testing, and the couple should be informed of available data on risk for sexual transmission of HCV to assist them in making decisions about precautions, including the low, but not absent, risk for transmission. HCV-positive persons do not need to avoid pregnancy or breastfeeding, and determining the need for cesarean delivery vs. vaginal delivery should not be made on the basis of HCV infection status. There are no recommendations for routine restriction of professional activities for HCV-infected health-care workers, and persons should not be excluded from work, school, play, child-care or other settings on the basis of their HCV infection status. 

References

FULL-TEXT ARTICLE
1. 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(No. RR-19):1–33.

2. Alter MJ, Kruszon-Moran D, Nainan OV, et al. Prevalence of hepatitis C virus infection in the United States. N Engl J Med 1999;341:556–62.

3. Polish LB, Tong MJ, Co RL, et al. Risk factors for hepatitis C virus infection among health care personnel in a community hospital. Am J Infect Control 1993;21:196–200.

4. Panlilio AL, Shapiro CN, Schable CA, et al. Serosurvey of human immunodeficiency virus, hepatitis B virus, and hepatitis C virus infection among hospital-based surgeons. J Am Coll Surg 1995;180:16–24.