High levels of hepatitis C virus (HCV) can be found in the rectal and nasal fluids of people with high hepatitis C viral loads even when blood is not present, Austrian researchers reported on Sunday at the 2018 AASLD Liver Meeting.
The findings reinforce the plausibility of HCV transmission through sharing of rolled-up bank notes or other materials for snorting drugs. They also support the hypothesis that rectal bleeding is not needed for the sexual transmission of HCV during anal intercourse.
The findings were presented by Dr David Chromy of the Medical University of Vienna on behalf of the Vienna HIV & Liver Study Group.
Previous research has shown that in men who have sex with men who have hepatitis C and HIV co-infection, HCV can be detected in semen and is associated with a higher HCV viral load in blood. A study of men who have sex with men with co-infection in New York found that approximately half had detectable HCV in their rectal fluid and this was associated with having a high HCV viral load.
The new study looked at levels of HCV RNA in rectal fluid and nasal fluid in 47 adults (23 who have sex with men, 17 heterosexual men and 7 women), 42 of whom were HIV positive. Participants were required to have detectable HCV viral load (RNA) in blood. The median HCV viral load of participants was 6.03 log IU/ml (just over 1 million IU/ml). Thirty-two per cent of participants were acutely infected with HCV. Dr Chromy said that a majority of cases of acute infection were detected in men who have sex with men.
Rectal and nasal fluid were sampled by swabs and the study excluded anyone with a rectal or nasal infection or other condition that might contaminate the swab with blood. (Rectal fluid was sampled from the mucous membrane lining the rectum.)
Seventy per cent of participants provided at least one rectal or nasal sample that was positive for HCV RNA. Participants were somewhat more likely to provide a positive nasal sample (62% of all participants) than a positive rectal sample (47% of all participants). The median viral load was significantly higher in people who tested positive (6.28 log IU/mL vs. 4.08 log IU/mL; p < 0.001). The median HCV RNA was higher in nasal samples (2.76 log IU/ml) than rectal samples (1.78 log IU/ml). These levels of HCV would be sufficient to transmit the virus.
Detection of HCV RNA was not dependent on HIV status, on recent HCV infection or on possible route of acquisition.
Thirty-two study participants provided information about possible risks for HCV acquisition or transmission during the preceding six months. Sixty-nine per cent reported nasal drug use and just under half of these participants reported sharing sniffing equipment. Thirty-one per cent reported injecting drug use but sharing of injecting equipment was far less common than sharing sniffing equipment (6%).
Two-thirds reported receptive anal intercourse but only 6% reported frequent use of condoms.
Dr Chromy said that “unprotected anal intercourse and sharing of drug-sniffing tools represent high-risk practices for HCV transmission in viremic patients,” and that patients need to be warned of the potential risks.
Chromy D et al. HCV-RNA is readily detectable in nasal and rectal fluids of patients with high viremia. AASLD Liver Meeting, San Francisco, abstract 202, 2018.
Update: Following the conference presentation, this research was published in a peer-reviewed journal:
Chromy D et al. HCV-RNA is commonly detectable in rectal and nasal fluids of patients with high viremia. Clinical Infectious Diseases, online ahead of print, 2019.