A recent spate of hepatitis C infections in gay men in European capitals is causing a re-evaluation of just how readily the virus can be transmitted through sexual activity. It may be that anal sex and other sexual practices such as “fisting” carry a higher risk of infection.

The widely held view has been that it is possible but difficult to transmit hepatitis C (HCV) through sexual activity, with no more than 5 percent of new infections occurring that way. The evidence had been gathered from heterosexual married couples engaging in vaginal intercourse where one person was infected with HCV. Even after decades of sexual exposure, there were very few examples of transmission to the other.

But outbreaks of HCV have been reported among HIV-infected gay men in London, Berlin, Paris and Amsterdam over the last few years. The most recent updates were presented at the retroviral conference in Denver in February.

Mark Danta said 213 HIV-positive gay men have been diagnoses with acute (very recent) HCV infections in London, and another 35 in the beach resort city of Brighton. Sequencing the viral genotype produced five clusters, “strong evidence for a common source of transmission” for hepatitis C, Danta said.

Comparisons of these viral strains with other known strains of HCV showed little difference in the genome that would make them more virulent. Since the virus hadn’t changed, the explanation for the increased number of infections probably had something to do with what the men were doing, he added.

Analyzing case histories of their sexual practices, it became clear that multiple partners, unprotected receptive anal intercourse, and especially engaging in fisting as both top and bottom, plus the use of club drugs, particularly cocaine and crystal meth, all predicted a greater likelihood of becoming infected with HCV. Danta suggested that the intersection of sex and drugs was the epicenter of risk.

He said that co-infection with HIV increases the level of HCV in seminal fluid, which also is likely to contribute to increased risk of transmission.

Thijs van de Laar reported on an increase in HCV infection after 2000 in an Amsterdam cohort of HIV-positive gay men that he has tracked since 1984. He performed similar genetic analysis of the virus, and a behavioral survey, and reached similar conclusions on risk factors. He also linked some of the infections to each other through contact tracing.

“I don’t think it is the virus,” van de Laar later said at a news conference. He suggested that anal drug use, including cocaine and crystal meth (known as “booty bumps”) may reduce the protection from infection provided by rectal mucosa. Both drugs are known to dry out mucosal tissue in the nose and mouth when snorted.

Another part of the explanation for the increase may be that the sexual practices did not change, but once HCV was introduced into this circle of gay men, continuing those practices spread the infection at least moderately well.

Similar patters of HCV infection have not been seen among HIV-positive gay men in the U.S., but that may be simply because no one has bothered to look. That has been a bone of contention for New York AIDS advocate Jules Levin, who has pushed for such surveillance to be undertaken. Van de Laar said, “If you don’t look, you don’t find it.”

Hepatitis C infection can be asymptomatic for decades before producing symptoms of liver disease that might draw the attention of a doctor or patient. One must test for the presence of the virus or its antibodies. People already infected with HIV should be particularly wary of HCV, because the added stress on the liver can complicate the metabolism of drugs and the treatment of both infections.

The accuracy of the OraQuick saliva test to detect antibodies to HIV was thrown into question last year when a number of clinics reported a higher than expected number of false positive results. That created a crisis in confidence, and some testing sites, such as the Los Angles Gay & Lesbian Center, stopped using the test to screen for HIV.

Bernard Branson presented the CDC’s exhaustive review of more than 25,000 tests at clinic sites across the country. It said the FDA requires a minimum of 98 percent specificity for rapid HIV tests. OraQuick had 99.9 percent specificity when used on blood, and 99.6 percent specificity when used on saliva, well above the FDA minimum threshold.

“The false positives appear to be related to unidentified site- or host-specific factors,” Branson said. “There was no evidence for a lab related or a device related problem.”

He said the rate of false positives tends to go up if the test is used after its expiration date, and the marker dye can flow back down if the instrument is kept upright in its stand for an extended period after the 20 minutes required to generate results.

“None of them would occur if you are following the manufacturer’s instructions,” he added.

Branson also said it is important to offer people a variety of testing options as some are reluctant to have blood drawn or their finger pricked, and for that reason the saliva test is a good option. The New York health department reported a 30-percent increase in willingness to voluntarily test for HIV once they added the oral test to the finger prick test.

Part of the concern of the accuracy of the OraQuick test may relate to the fact that the company that makes it is seeking FDA approval to sell it over the counter in drugstores. Many AIDS organizations provide HIV counseling and testing and may feel threatened by a product that reduces the need for their services.

Branson acknowledged after his presentation that “counseling and testing is the bread and butter” of many of these organizations. He thought it “peculiar” that questions about the accuracy of the test only arose after the manufacturer approached the FDA about making it directly available to consumers.