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Hepatitis C transmitted during sexual contact

Hepatitis C is not only transmitted in blood, but apparently also by sexual contact. This is shown by a HIV-patient study supported by the Swiss National Science Foundation (SNSF).

Until a few years ago, scientific opinion held that Hepatitis C (HCV) was only transmitted in the blood, and therefore almost exclusively through blood transfusions or when injecting drugs with contaminated needles. However, scientists then discovered that increasing numbers of homosexual HIV patients, also in Switzerland, were suffering from Hepatitis C, alongside intravenous drug users.

Roger Kouyos, Huldrych Günthard and their team at the University Hospital Zurich have now investigated whether this increase is due to transmission during sexual contact. They compared the molecular structure of HI viruses in almost 10,000 anonymised samples from patients participating in the Swiss HIV Cohort Study. Where two patients share matching virus gene sequences, it is highly probable that one was infected by the other. The researchers were able to establish more than 1,500 pairs of patients, about whom it was additionally known whether they were also infected with Hepatitis C.

Three times the risk

Analysis of the data revealed that HIV patients with a HIV/HCV positive partner are between two and three times more likely to be infected with Hepatitis C than is the case for other HIV positive patients. This increased risk was observed not only among drug addicts, but also among homosexual and heterosexual HIV patients. "This is an indication of sexual transmission of Hepatitis C," explained Roger Kouyos, the lead author of the recently published study (*).

These findings are important for prevention. “HIV positive people who have Hepatitis C should not have unprotected sex,” said Huldrych Günthard, president of the HIV Cohort Study. Homosexuals appear to be particularly at risk. The reasons why remain unclear, according to the researchers. "One potential explanation is that anal sex results in increased blood exchange between partners," said Günthard.

Serious consequences take years to appear

It remains to be seen whether Hepatitis C infections are also increasing among non-HIV patients. Four out of five HCV cases show no symptoms in the weeks and months following infection. Visible, serious consequences take years to appear: up to half of those infected develop liver cirrhosis. Günthard said that this demonstrates the value of a cohort study, in which the patients are studied repeatedly over the course of many years. “We can only recognise Hepatitis C infections at an early stage because the patients in the HIV Cohort Study are subject to regular blood testing and screenings.”

(*) Roger D. Kouyos, Andri Rauch, Jürg Böni, Sabine Yerly, Cyril Shah, Vincent Aubert, Thomas Klimkait, Helen Kovari, Alexandra Calmy, Matthias Cavassini, Manuel Battegay, Pietro L. Vernazza, Enos Bernasconi, Bruno Ledergerber, Huldrych F. Günthard and the Swiss HIV Cohort Study (2014). Clustering of HCV coinfections on HIV phylogeny indicates domestic and sexual transmission of HCV. International Journal of Epidemiology online.
doi: 10.1093/ije/dyt276 (Available to journalists as a PDF file from the SNSF: com@snf.ch)

The Swiss HIV Cohort

The aim of the study, which started in 1988, is to better understand HIV infection and AIDS, and improve the treatment of patients. All of Switzerland’s specialist HIV clinics (Basel, Bern, Geneva, Lausanne, Lu-gano, St. Gallen and Zurich) collect data on the treatment and progress of the disease. Currently over 8,800 people are taking part in the Swiss HIV Cohort Study, of whom almost one third are women.

Contact

Dr Roger Kouyos
Division of Infectious Diseases and Hospital Epidemiology
University Hospital Zurich
Rämistrasse 100
CH-8091 Zurich
Phone +41 44 255 36 10
E-mail roger.kouyos@usz.ch

Prof Dr med Huldrych Günthard
Division of Infectious Diseases and Hospital Epidemiology
University Hospital Zurich
Phone +41 44 255 34 50
E-mail huldrych.guenthard@usz.ch

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