Sexual Activity as a Risk Factor for HCV

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Sexual Activity as a Risk Factor for HCV

Alan Franciscus Editor-in-Chief, HCV Advocate

Percutaneous exposures, such as injection drug use or a blood

transfusion prior to effective screening are well-documented risk

factors for HCV, hepatitis B and HIV transmission. There are,

however, clear differences between these viruses when it comes to

their ability to be transmitted through sexual activity. There is an

adequate amount of evidence indicating that HCV can be sexually

transmitted but with much less efficiency than both hepatitis B and

HIV.

To date the epidemiological studies evaluating the degree of risk of

HCV transmission by sexual contact have had quite a few

methodological limitations that are inclined to overestimate the

amount of HCV infections associated with sexual contact. Early

studies used first-generation anti-HCV assays, which have a higher

false positive rate than second and third-generation assays. Studies

vary in the completeness of risk ascertainment and many fail to

carefully exclude HCV acquirement from non-sexual sources. Non-

disclosure of injection drug use (IDU) as a risk factor is

particularly important since assessing the contribution of sexual

activity to HCV transmission is difficult in the presence of

injection drug use. Finally, only a limited number of studies perform

virological analyses to confirm that sexual partners are infected

with the same virus thereby excluding acquirement from outside

sources.

Sexual transmission of virus occurs when infected body secretions or

infected blood are exchanged across mucosal surfaces. The presence of

virus in body secretions is necessary but may not be sufficient for

transmission to occur. Other factors that may influence transmission

include the titer or amount of virus in body secretions (body

secretion viral load), the integrity of the mucosal surfaces (some

sexual practices may traumatize the mucosa, e.g., anal receptive sex

and fisting), and the presence of other genital infections, both

viral or bacterial including herpes simplex virus, trichomonas and

gonorrhea.

Studies to detect HCV RNA in semen (seminal fluid and cells), vaginal

secretions, cervical smears, and saliva have produced mixed results.

Inability to detect HCV RNA in body secretions may be caused by

technical aspects, including specimen collection and storage, and the

ability to exclude cellular components and surmount the presence of

polymerase chain reaction inhibitors. Even in studies using the most

favorable methods for isolating HCV RNA, the majority of samples were

negative for HCV RNA and those that were positive were of low titer

(equal to 1000 copies/mL). A low titer of virus in genital secretions

could explain why HCV is transmitted less efficiently than hepatitis

B virus or HIV. Furthermore, there may be a lack of suitable target

cells in the genital tract to allow infection to occur or infection

may require the presence of abnormal mucosa (ruptured or damaged

mucosa which would result from sexual injury or a bacterial or viral

infection). Finally, while the presence of HCV RNA in semen, vaginal

or cervical secretions supports the argument that HCV is sexually

transmissible, a cell culture system or animal model is still needed

to prove that HCV RNA detected in genital secretions represents

infectious virus.

Sexual transmission has been assessed in varying populations of HCV

infected individuals, and two main risk groups have been identified.

The first risk group comprises those who have more sexual encounters

and who are more likely to have multiple sexual partners, including

men who have sex with men, female sex workers, attendees of sexually

transmitted disease clinics, and those in HIV surveillance studies.

The second risk group comprises persons who are in a long-term

monogamous sexual relationship with someone who is chronically

infected with HCV. There are differences in the rates of anti-HCV

positivity by risk group with higher rates reported for the first

risk group. These differences in rates of HCV infection may correlate

with differences in sexual risk behaviors including and not limited

to frequency or type of sexual activities. On the other hand,

differences between risk groups may indicate inconsistent rates of

exposure to non-sexual sources of HCV including injection drug use,

intranasal cocaine use, tattooing, body piercing, dental exposure,

toothbrushes, razors, etc. For this reason, sexual transmission

findings from one risk group cannot be considered as widespread fact.

With that said, it has been found consistently in both prospective

and retrospective studies that the risk of HCV transmission via

sexual contact differs by the type of sexual relationship. Among

individuals with multiple partners or those at risk for sexually

transmitted diseases (STDs), the median seroprevalence of antibody to

HCV is 4% (range, 1.6% to 25.5%) with the median rates being 6%

(range, 1% to 19%) among female sex workers, 4% among men who have

sex with men (range, 2.9% to13%), and 4% among attendees of STD

clinics as well as individuals participating in HIV surveillance

studies (range, 1.6% to 26%, which dropped to a range of 1.6% to 7%

when limited to individuals without a history of IDU). HIV

coinfection increases the rate of HCV transmission by sexual contact

even though the precise mechanism is unknown.

Persons in long-term monogamous partnerships, on the other hand, are

at lower risk of acquiring HCV (0% to 0.6% per year) than persons

with multiple partners or those at risk for sexually transmitted

diseases (0.4% to 1.8% per year). This difference may reflect

differences in sexual risk behaviors or differences in rates of

exposure to nonsexual sources of HCV. Early studies found that the

rate of HCV positivity in partners increased with the longer duration

of marriage, suggesting that the risk of sexual transmission

correlated with frequency of contact. However subsequent studies

adjusting for age did not find a consistent relationship between the

duration of the sexual relationship and the HCV positivity of the

partners. Overestimation of the rate of sexual transmission of HCV

occurs when antibody testing alone is used to make the assessment.

So, based on only those seroprevalence studies that used genotyping

or sequence analysis of the hypervariable region of E2 (the envelope

region of the HCV genome), in monogamous, heterosexual partners of

hepatitis C-infected, HIV-negative persons, the frequency of antibody-

positive and genotype-concordant couples is 2.8% to 11% in Southeast

Asia, 0% to 6.3% in Northern Europe, and 2.7% in the United States.

The mounting evidence indicates that HCV virus can be transmitted by

sexual contact but much less efficiently than other sexually

transmitted viruses, including both the hepatitis B and the HIV

viruses. However, because sex is such a common behavior and the

numbers of HCV-infected individuals in the United States is

substantial, sexual transmission of HCV likely contributes to the

total burden of infection in the United States. Current

recommendations about sexual practices are different for persons with

chronic HCV infection who are in steady monogamous partnerships

versus those with multiple partners or who are in short-term sexual

relationships. HCV positive individuals in longer-term monogamous

relationships need not change their sexual practices although they

should discuss safer sex options if either partner is concerned about

sexual transmission. If couples wish to reduce the already low risk

of HCV transmission by sexual contact, barrier precautions may be

used. Partners of HCV-positive persons should be considered for anti-

HCV testing. For HCV-infected individuals with multiple or short-term

sexual partners, barrier methods or abstinence are recommended.

Copyright April 2003 Hepatitis C Support Project All Rights

Reserved. Permission to reprint is granted and encouraged with credit

to the Hepatitis C Support Project