A new study of married couples suggests that the hepatitis C virus (HCV) can be transmitted through sexual intercourse. However, the investigators in Turkey also found that the risk is not very strong.

The findings are published in the April issue of the American Journal of Gastroenterology.¹

HCV Transmission: Elusive In Some Cases
Contact with infected blood is the primary route of hepatitis C transmission, noted lead investigator Veysel Tahan, MD,  in the department of Gastroenterology at Marmara University in Istanbul, Turkey, and his colleagues. Still, in up to 50% of cases, doctors fail to identify a transmission route.

Whether HCV can be sexually transmitted is controversial, the researchers pointed out. "The sexual transmission of hepatitis C virus is debated. By excluding other risk factors, the role of sexual intercourse in the transmission could be detected more accurately," they wrote.

To answer this question, Tahan and his fellow researchers enrolled 600 spouses of people diagnosed with hepatitis C for their study.

In order to eliminate other possible risk factors for hepatitis C that could mar the link between sexual intercourse and HCV transmission, Tahan and his team interviewed each spouse about risk factors other than sexual intercourse. Each spouse also underwent an antibody test for HCV. Antibodies are substances released by the immune system to fight off infection from an invading disease-causing organism. When antibodies specific to HCV are detected, it tells the doctor that the patient has the viral infection.

Positive Versus Negative HCV Tests
Tahan and his associates found that 12 of the 600 spouses tested positive for HCV; that translates to about 2 percent of them. Of those, 11 also tested positive for HCV RNA, a more sensitive test used to detect the virus' genetic material as a sign of its presence.²

The researchers also wanted to determine if any patients who had tested negative for HCV antibodies would eventually test positive—known in medical terms as seroconversion. To do this, the study team followed a separate group of 216 spouses for nearly 3 years, on average, who had initially tested negative for HCV antibodies. At the end of the follow-up period, none of those spouses became positive.

Sexual Intercourse: Transmission Route?
Of the 12 patients who tested positive for hepatitis C at the beginning of the study, Tahan and his colleagues noted that age and the length of each couple's marriage had no effect on the risk of contracting hepatitis C. However, there was a near-significant association between the number of times each couple had had intercourse and the risk of contracting HCV. "This is the first study that stresses the importance of the total number of sexual intercourse in sexual transmission," the investigators wrote.

Weak Link Found
Based on the numbers of people who tested positive for hepatitis C in this study, the risk noted was relatively weak. That conclusion has also been drawn in other research.

In a study from Italy last year that followed nearly 900 monogamous couples in which one partner was infected with HCV,³ researchers conducted follow-up exams over 10 years to determine if the spouse of an infected patient became positive during that time. 

Only three cases of HCV were found, but in one instance, a spouse's genotype was different than that of the partner, "clearly excluding sexual transmission," the researchers wrote. The other two spouses had different viral isolates, or components, than their partners, again excluding the possibility of sexual transmission.

In conclusion, the investigators say the risk of sexually transmitting HCV is "extremely low or even null."

In an earlier study,⁴ researchers followed 311 spouses whose partners were HCV positive. At the end of the study, 32 (about 10 percent) of the spouses tested positive for hepatitis C. However, they reported other types of exposure, such as blood transfusion, drug use, and use of multiple-glass syringes, more often than the 279 spouses who had tested negative for HCV.

Among 13 couples who both tested HCV RNA positive, the same genotype was found in both partners in only 8 cases, meaning sexual transmission occurred in very few instances, if it occurred at all.

"The findings that the same genotype was detected for both partners in relatively few couples, and that a history of exposure [by injection] was an independent predictor of HCV positivity, suggest that the risk of sexual transmission is low," the study authors wrote.

1. Tahan V, Karaca C, Yildirim B et al. Sexual transmission of HCV between spouses. Am J Gastroenterol 2005 Apr;100(4):821-4.
2. Hepatitis Neighborhood. Hepatitis C Viral Load Testing. Available at: http://www.hepatitisneighborhood.com/content/
understanding_hepatitis/diagnosing_hepatitisc_135.aspx. Accessed May 12, 2005.
3. Vandelli C, Renzo F, Romano L 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 2004May;99(5):855-9.
4. Stroffolini T, Lorenzoni U, Menniti-Ippolito F, Infantolino D, Chiaramonte M. Hepatitis C virus infection in spouses: sexual transmission or common exposure to risk factors? Am J Gastroenterol 2001 Nov;96(11):3138-41.

John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include overseeing health news coverage for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.