Sexual Transmission of Hepatitis C: What is the Evidence?

[Guest guest]

Sexual Transmission of Hepatitis C:

What is the Evidence? Dr. Dore

A recent article in The New England Journal of

Medicine first authored by Dr. Miriam Alter, the chief

hepatitis epidemiologist (disease transmission

researcher) from the Centers for Disease Control and

Prevention in Atlanta, GA, USA; claimed an independent

association (a linking factor, in its own right)

between hepatitis C infection and number of lifetime

sexual partners (Alter M et al. NEJM 341:556-62,

1999). It also claimed that 20-25% of all hepatitis C

infections in the United States were acquired through

sexual contact.

The study, a random household survey, involved

interviews, physical examination, and collection of

blood specimens to assess the health and nutritional

status of Americans - hepatitis C was only one of

numerous diseases evaluated. Among adults, hepatitis C

prevalence was 1.8%, with independent associations

including education level, poverty index, marijuana

use, cocaine use, number of sexual partners, and age

at first sexual intercourse. The study collected

extensive data, but failed to ask the crucial question

of " have you ever injected illicit drugs? " .

The authors were happy to acknowledge that having the

odd joint or bong was not a biologically plausible

explanation for transmission of hepatitis C, [when

saying that] " marijuana use serves as a surrogate for

other methods of transmission (such as injection-drug

use and high-risk sexual practices). " However, there

is a much more obvious form of " surrogacy " represented

by their results - it is likely that most, if not all,

of the factors associated with higher levels of

hepatitis C prevalence (poor education level, poverty,

cocaine use, increased number of sexual partners and

early age of first sexual intercourse) were also

strongly associated with injecting drug use.

In a letter responding to their article we stated that

the apparent association between hepatitis C and

number of sexual partners was an example of

epidemiological confounding [something that skews or

distorts a research study] (Dore G et al. NEJM

341:2093-4, 1999). In particular, it is likely that

people reporting a higher number of sexual partners

were, as a group, more likely to have a history of

injecting, than those who had few partners. We argued

that even in other studies where the question " have

you ever injected illicit drugs? " has been asked,

people are often not willing to answer correctly.

In an environment such as the United States, where

drug use in general, and injecting, in particular, are

highly stigmatized, it would not be surprising to see

substantial under-reporting of injecting drug use. We

also outlined the evidence against significant levels

of hepatitis C transmission through sexual contact.

So, what is the current state of evidence around

sexual transmission of hepatitis C? An examination of

this evidence is essential in order to inform a person

with hepatitis C and his or her partners about the

risk of sexual transmission, whatever that risk. On

purely biological grounds, it is plausible that

hepatitis C could be transmitted sexually. Although

semen and vaginal secretions themselves probably

contain little, if any, hepatitis C virus (Caldwell S,

et al. Liver Trans Surg 2:124-9, 1996), sexual contact

may well involve some degree of blood contact, for

example, if sex takes place during a woman's

menstruation, or involves some degree of trauma.

It is another matter altogether to demonstrate that

sexual transmission of hepatitis C actually occurs, or

if it does, that it occurs with a sufficiently high

probability to be of concern to people with hepatitis

C and their partners.

Several types of studies have been used to investigate

the sexual transmission of hepatitis C: Cases of

people diagnosed with hepatitis C, self-reporting how

they felt they contracted the condition. Although a

high proportion of cases are associated with a history

involving the potential for blood contact,

predominantly through sharing of injecting equipment,

cases without such a history may be attributed to

sexual transmission.

In the United States, 20-25% of people with acute

hepatitis C are considered to have acquired their

infection through sexual contact (Alter M and Moyer L.

J AIDS 18(suppl 1):S6-S10, 1998). Many of these people

give a history of sexual contact with a person with

hepatitis C, but deny other risk factors such as

sharing injecting equipment.

In contrast, among a series of 467 people newly

diagnosed with hepatitis C from the north coast of New

South Wales, all but one reported actual or potential

blood exposures (injecting drug use, 85%; pre-1990

blood transfusion, 6%; blood exposures, 8%). None of

the cases reported sexual contact as their only

possible exposure (Sladden T, et al. MJA 166:290-293,

1997). Of 54 partners who tested positive for

hepatitis C and were questioned about risk factors,

all had potential blood exposure. Why the disparity

between studies in the United States and Australia, in

settings where, presumably, sexual behavior and

practices are quite similar?

Under reporting of injecting drug use is the obvious

explanation. Although injecting drugs undoubtedly is

stigmatized in Australia, in the United States there

is almost certainly greater stigmatization of illicit

drug use. Hardened sentencing for drug-related crimes

in recent years, and a general mistrust of those in

authority, may have also contributed to greater under

reporting of illegal activities. In contrast, the

north coast of New South Wales is probably an area

where stigmatization of drug use is relatively low,

and trust of researchers and those in authority may be

relatively high.

Prevalence in people at sexual risk

Certain population groups are recognized as being at

higher risk of sexually transmissible infections, and

would be expected to have higher rates of hepatitis C

if it was indeed sexually transmissible. Female sex

workers and homosexual men are probably the groups

most often considered in such studies, which have

generally not found increases in the levels of

hepatitis C that would be consistent with an agent

that is readily sexually transmissible.

In a study among gay men in Sydney (Bodsworth N, et

al. Genitourin Med 72:118-22 1996), although the

prevalence of hepatitis C (7%) was considerably higher

than estimates of the general adult male population

prevalence (2%) (ANCARD 1998), there was no

association between hepatitis C and either number of

sexual partners or sexual practices. The higher rates

of injecting drug use, and not sexual behavior, among

Sydney gay men are almost certainly the explanation

for this higher hepatitis C prevalence.

Cross-sectional partner studies

Several studies over the past decade have found that

the spouses or regular sexual partners of people

diagnosed with hepatitis C have higher levels of

hepatitis C than found in the general population. The

prevalence in partners has also been found to be

related to the duration of the sexual relationship.

Such studies, based on testing at one time point, may

suggest transmission associated with stable

partnerships, but whether it is sexual contact, other

forms of contact involving blood, or a common

antecedent history such as unsterilized medical

injections in both partners is difficult to establish.

Longitudinal partner studies

The most convincing evidence for or against sexual

transmission should come from longitudinal partner

studies, in which one member of the couple is known to

have hepatitis C at the start, the other is known or

can be assumed not to be infected, and forms of blood

contact not involving sex can be convincingly

excluded. So far, very few such studies have been

reported. Two studies of the sexual partners of

several hundred women infected through contaminated

anti-D immunoglobulin injections given following

childbirth in 1977-1978, in Germany and Ireland and

with average duration of relationships of 10-15 years

found no cases of probable sexual transmission (Meisel

H et al. Lancet 345:1209-11, 1995; Power J et al.

Lancet 344:1166-7, 1994).

What does an examination of these studies deduce with

respect to sexual transmission of hepatitis C? If the

question is " can hepatitis C be transmitted through

sexual contact? " then the answer almost certainly is

yes. If the question is " what is the level of risk of

hepatitis C transmission through sexual contact? " ,

then the answer is extremely low to negligible. Are

there circumstances in which sexual transmission may

be more likely? The answer to this question is based

on plausibility rather than direct evidence, but,

circumstances in which blood contact is more likely,

such as sexual contact during menstruation, involving

traumatic sexual practices and in the presence of

genital ulceration, may introduce a significant risk

of sexual transmission of hepatitis C.

And finally, but most importantly, what advice should

be given to people with hepatitis C and their sexual

partners? My advice is that for people in stable

relationships, condoms are not necessary. Although I

believe menstruation (whether the female or male

partner has hepatitis C) to be a low risk setting for

sexual transmission, either use of condoms or

abstinence from vaginal sex is probably a reasonable

policy. With regard to sexual contact with casual

partners, my advice would be that condom use is

sensible, more for protection from other truly

sexually transmissible infections.

Dr Dore, Lecturer in Epidemiology, Infectious

Diseases Physician, National Centre in HIV

Epidemiology and Clinical Research, University of New

South Wales. Abridged with thanks from the fully

referenced original in the Australian Hepatitis

Chronicle, Issue 4 March 2000: 2-5.

__________________________________________________

[Guest guest]

Sexual Transmission of Hepatitis C:

What is the Evidence? Dr. Dore

A recent article in The New England Journal of

Medicine first authored by Dr. Miriam Alter, the chief

hepatitis epidemiologist (disease transmission

researcher) from the Centers for Disease Control and

Prevention in Atlanta, GA, USA; claimed an independent

association (a linking factor, in its own right)

between hepatitis C infection and number of lifetime

sexual partners (Alter M et al. NEJM 341:556-62,

1999). It also claimed that 20-25% of all hepatitis C

infections in the United States were acquired through

sexual contact.

The study, a random household survey, involved

interviews, physical examination, and collection of

blood specimens to assess the health and nutritional

status of Americans - hepatitis C was only one of

numerous diseases evaluated. Among adults, hepatitis C

prevalence was 1.8%, with independent associations

including education level, poverty index, marijuana

use, cocaine use, number of sexual partners, and age

at first sexual intercourse. The study collected

extensive data, but failed to ask the crucial question

of " have you ever injected illicit drugs? " .

The authors were happy to acknowledge that having the

odd joint or bong was not a biologically plausible

explanation for transmission of hepatitis C, [when

saying that] " marijuana use serves as a surrogate for

other methods of transmission (such as injection-drug

use and high-risk sexual practices). " However, there

is a much more obvious form of " surrogacy " represented

by their results - it is likely that most, if not all,

of the factors associated with higher levels of

hepatitis C prevalence (poor education level, poverty,

cocaine use, increased number of sexual partners and

early age of first sexual intercourse) were also

strongly associated with injecting drug use.

In a letter responding to their article we stated that

the apparent association between hepatitis C and

number of sexual partners was an example of

epidemiological confounding [something that skews or

distorts a research study] (Dore G et al. NEJM

341:2093-4, 1999). In particular, it is likely that

people reporting a higher number of sexual partners

were, as a group, more likely to have a history of

injecting, than those who had few partners. We argued

that even in other studies where the question " have

you ever injected illicit drugs? " has been asked,

people are often not willing to answer correctly.

In an environment such as the United States, where

drug use in general, and injecting, in particular, are

highly stigmatized, it would not be surprising to see

substantial under-reporting of injecting drug use. We

also outlined the evidence against significant levels

of hepatitis C transmission through sexual contact.

So, what is the current state of evidence around

sexual transmission of hepatitis C? An examination of

this evidence is essential in order to inform a person

with hepatitis C and his or her partners about the

risk of sexual transmission, whatever that risk. On

purely biological grounds, it is plausible that

hepatitis C could be transmitted sexually. Although

semen and vaginal secretions themselves probably

contain little, if any, hepatitis C virus (Caldwell S,

et al. Liver Trans Surg 2:124-9, 1996), sexual contact

may well involve some degree of blood contact, for

example, if sex takes place during a woman's

menstruation, or involves some degree of trauma.

It is another matter altogether to demonstrate that

sexual transmission of hepatitis C actually occurs, or

if it does, that it occurs with a sufficiently high

probability to be of concern to people with hepatitis

C and their partners.

Several types of studies have been used to investigate

the sexual transmission of hepatitis C: Cases of

people diagnosed with hepatitis C, self-reporting how

they felt they contracted the condition. Although a

high proportion of cases are associated with a history

involving the potential for blood contact,

predominantly through sharing of injecting equipment,

cases without such a history may be attributed to

sexual transmission.

In the United States, 20-25% of people with acute

hepatitis C are considered to have acquired their

infection through sexual contact (Alter M and Moyer L.

J AIDS 18(suppl 1):S6-S10, 1998). Many of these people

give a history of sexual contact with a person with

hepatitis C, but deny other risk factors such as

sharing injecting equipment.

In contrast, among a series of 467 people newly

diagnosed with hepatitis C from the north coast of New

South Wales, all but one reported actual or potential

blood exposures (injecting drug use, 85%; pre-1990

blood transfusion, 6%; blood exposures, 8%). None of

the cases reported sexual contact as their only

possible exposure (Sladden T, et al. MJA 166:290-293,

1997). Of 54 partners who tested positive for

hepatitis C and were questioned about risk factors,

all had potential blood exposure. Why the disparity

between studies in the United States and Australia, in

settings where, presumably, sexual behavior and

practices are quite similar?

Under reporting of injecting drug use is the obvious

explanation. Although injecting drugs undoubtedly is

stigmatized in Australia, in the United States there

is almost certainly greater stigmatization of illicit

drug use. Hardened sentencing for drug-related crimes

in recent years, and a general mistrust of those in

authority, may have also contributed to greater under

reporting of illegal activities. In contrast, the

north coast of New South Wales is probably an area

where stigmatization of drug use is relatively low,

and trust of researchers and those in authority may be

relatively high.

Prevalence in people at sexual risk

Certain population groups are recognized as being at

higher risk of sexually transmissible infections, and

would be expected to have higher rates of hepatitis C

if it was indeed sexually transmissible. Female sex

workers and homosexual men are probably the groups

most often considered in such studies, which have

generally not found increases in the levels of

hepatitis C that would be consistent with an agent

that is readily sexually transmissible.

In a study among gay men in Sydney (Bodsworth N, et

al. Genitourin Med 72:118-22 1996), although the

prevalence of hepatitis C (7%) was considerably higher

than estimates of the general adult male population

prevalence (2%) (ANCARD 1998), there was no

association between hepatitis C and either number of

sexual partners or sexual practices. The higher rates

of injecting drug use, and not sexual behavior, among

Sydney gay men are almost certainly the explanation

for this higher hepatitis C prevalence.

Cross-sectional partner studies

Several studies over the past decade have found that

the spouses or regular sexual partners of people

diagnosed with hepatitis C have higher levels of

hepatitis C than found in the general population. The

prevalence in partners has also been found to be

related to the duration of the sexual relationship.

Such studies, based on testing at one time point, may

suggest transmission associated with stable

partnerships, but whether it is sexual contact, other

forms of contact involving blood, or a common

antecedent history such as unsterilized medical

injections in both partners is difficult to establish.

Longitudinal partner studies

The most convincing evidence for or against sexual

transmission should come from longitudinal partner

studies, in which one member of the couple is known to

have hepatitis C at the start, the other is known or

can be assumed not to be infected, and forms of blood

contact not involving sex can be convincingly

excluded. So far, very few such studies have been

reported. Two studies of the sexual partners of

several hundred women infected through contaminated

anti-D immunoglobulin injections given following

childbirth in 1977-1978, in Germany and Ireland and

with average duration of relationships of 10-15 years

found no cases of probable sexual transmission (Meisel

H et al. Lancet 345:1209-11, 1995; Power J et al.

Lancet 344:1166-7, 1994).

What does an examination of these studies deduce with

respect to sexual transmission of hepatitis C? If the

question is " can hepatitis C be transmitted through

sexual contact? " then the answer almost certainly is

yes. If the question is " what is the level of risk of

hepatitis C transmission through sexual contact? " ,

then the answer is extremely low to negligible. Are

there circumstances in which sexual transmission may

be more likely? The answer to this question is based

on plausibility rather than direct evidence, but,

circumstances in which blood contact is more likely,

such as sexual contact during menstruation, involving

traumatic sexual practices and in the presence of

genital ulceration, may introduce a significant risk

of sexual transmission of hepatitis C.

And finally, but most importantly, what advice should

be given to people with hepatitis C and their sexual

partners? My advice is that for people in stable

relationships, condoms are not necessary. Although I

believe menstruation (whether the female or male

partner has hepatitis C) to be a low risk setting for

sexual transmission, either use of condoms or

abstinence from vaginal sex is probably a reasonable

policy. With regard to sexual contact with casual

partners, my advice would be that condom use is

sensible, more for protection from other truly

sexually transmissible infections.

Dr Dore, Lecturer in Epidemiology, Infectious

Diseases Physician, National Centre in HIV

Epidemiology and Clinical Research, University of New

South Wales. Abridged with thanks from the fully

referenced original in the Australian Hepatitis

Chronicle, Issue 4 March 2000: 2-5.

__________________________________________________

[Guest guest]

Sexual Transmission of Hepatitis C:

What is the Evidence? Dr. Dore

A recent article in The New England Journal of

Medicine first authored by Dr. Miriam Alter, the chief

hepatitis epidemiologist (disease transmission

researcher) from the Centers for Disease Control and

Prevention in Atlanta, GA, USA; claimed an independent

association (a linking factor, in its own right)

between hepatitis C infection and number of lifetime

sexual partners (Alter M et al. NEJM 341:556-62,

1999). It also claimed that 20-25% of all hepatitis C

infections in the United States were acquired through

sexual contact.

The study, a random household survey, involved

interviews, physical examination, and collection of

blood specimens to assess the health and nutritional

status of Americans - hepatitis C was only one of

numerous diseases evaluated. Among adults, hepatitis C

prevalence was 1.8%, with independent associations

including education level, poverty index, marijuana

use, cocaine use, number of sexual partners, and age

at first sexual intercourse. The study collected

extensive data, but failed to ask the crucial question

of " have you ever injected illicit drugs? " .

The authors were happy to acknowledge that having the

odd joint or bong was not a biologically plausible

explanation for transmission of hepatitis C, [when

saying that] " marijuana use serves as a surrogate for

other methods of transmission (such as injection-drug

use and high-risk sexual practices). " However, there

is a much more obvious form of " surrogacy " represented

by their results - it is likely that most, if not all,

of the factors associated with higher levels of

hepatitis C prevalence (poor education level, poverty,

cocaine use, increased number of sexual partners and

early age of first sexual intercourse) were also

strongly associated with injecting drug use.

In a letter responding to their article we stated that

the apparent association between hepatitis C and

number of sexual partners was an example of

epidemiological confounding [something that skews or

distorts a research study] (Dore G et al. NEJM

341:2093-4, 1999). In particular, it is likely that

people reporting a higher number of sexual partners

were, as a group, more likely to have a history of

injecting, than those who had few partners. We argued

that even in other studies where the question " have

you ever injected illicit drugs? " has been asked,

people are often not willing to answer correctly.

In an environment such as the United States, where

drug use in general, and injecting, in particular, are

highly stigmatized, it would not be surprising to see

substantial under-reporting of injecting drug use. We

also outlined the evidence against significant levels

of hepatitis C transmission through sexual contact.

So, what is the current state of evidence around

sexual transmission of hepatitis C? An examination of

this evidence is essential in order to inform a person

with hepatitis C and his or her partners about the

risk of sexual transmission, whatever that risk. On

purely biological grounds, it is plausible that

hepatitis C could be transmitted sexually. Although

semen and vaginal secretions themselves probably

contain little, if any, hepatitis C virus (Caldwell S,

et al. Liver Trans Surg 2:124-9, 1996), sexual contact

may well involve some degree of blood contact, for

example, if sex takes place during a woman's

menstruation, or involves some degree of trauma.

It is another matter altogether to demonstrate that

sexual transmission of hepatitis C actually occurs, or

if it does, that it occurs with a sufficiently high

probability to be of concern to people with hepatitis

C and their partners.

Several types of studies have been used to investigate

the sexual transmission of hepatitis C: Cases of

people diagnosed with hepatitis C, self-reporting how

they felt they contracted the condition. Although a

high proportion of cases are associated with a history

involving the potential for blood contact,

predominantly through sharing of injecting equipment,

cases without such a history may be attributed to

sexual transmission.

In the United States, 20-25% of people with acute

hepatitis C are considered to have acquired their

infection through sexual contact (Alter M and Moyer L.

J AIDS 18(suppl 1):S6-S10, 1998). Many of these people

give a history of sexual contact with a person with

hepatitis C, but deny other risk factors such as

sharing injecting equipment.

In contrast, among a series of 467 people newly

diagnosed with hepatitis C from the north coast of New

South Wales, all but one reported actual or potential

blood exposures (injecting drug use, 85%; pre-1990

blood transfusion, 6%; blood exposures, 8%). None of

the cases reported sexual contact as their only

possible exposure (Sladden T, et al. MJA 166:290-293,

1997). Of 54 partners who tested positive for

hepatitis C and were questioned about risk factors,

all had potential blood exposure. Why the disparity

between studies in the United States and Australia, in

settings where, presumably, sexual behavior and

practices are quite similar?

Under reporting of injecting drug use is the obvious

explanation. Although injecting drugs undoubtedly is

stigmatized in Australia, in the United States there

is almost certainly greater stigmatization of illicit

drug use. Hardened sentencing for drug-related crimes

in recent years, and a general mistrust of those in

authority, may have also contributed to greater under

reporting of illegal activities. In contrast, the

north coast of New South Wales is probably an area

where stigmatization of drug use is relatively low,

and trust of researchers and those in authority may be

relatively high.

Prevalence in people at sexual risk

Certain population groups are recognized as being at

higher risk of sexually transmissible infections, and

would be expected to have higher rates of hepatitis C

if it was indeed sexually transmissible. Female sex

workers and homosexual men are probably the groups

most often considered in such studies, which have

generally not found increases in the levels of

hepatitis C that would be consistent with an agent

that is readily sexually transmissible.

In a study among gay men in Sydney (Bodsworth N, et

al. Genitourin Med 72:118-22 1996), although the

prevalence of hepatitis C (7%) was considerably higher

than estimates of the general adult male population

prevalence (2%) (ANCARD 1998), there was no

association between hepatitis C and either number of

sexual partners or sexual practices. The higher rates

of injecting drug use, and not sexual behavior, among

Sydney gay men are almost certainly the explanation

for this higher hepatitis C prevalence.

Cross-sectional partner studies

Several studies over the past decade have found that

the spouses or regular sexual partners of people

diagnosed with hepatitis C have higher levels of

hepatitis C than found in the general population. The

prevalence in partners has also been found to be

related to the duration of the sexual relationship.

Such studies, based on testing at one time point, may

suggest transmission associated with stable

partnerships, but whether it is sexual contact, other

forms of contact involving blood, or a common

antecedent history such as unsterilized medical

injections in both partners is difficult to establish.

Longitudinal partner studies

The most convincing evidence for or against sexual

transmission should come from longitudinal partner

studies, in which one member of the couple is known to

have hepatitis C at the start, the other is known or

can be assumed not to be infected, and forms of blood

contact not involving sex can be convincingly

excluded. So far, very few such studies have been

reported. Two studies of the sexual partners of

several hundred women infected through contaminated

anti-D immunoglobulin injections given following

childbirth in 1977-1978, in Germany and Ireland and

with average duration of relationships of 10-15 years

found no cases of probable sexual transmission (Meisel

H et al. Lancet 345:1209-11, 1995; Power J et al.

Lancet 344:1166-7, 1994).

What does an examination of these studies deduce with

respect to sexual transmission of hepatitis C? If the

question is " can hepatitis C be transmitted through

sexual contact? " then the answer almost certainly is

yes. If the question is " what is the level of risk of

hepatitis C transmission through sexual contact? " ,

then the answer is extremely low to negligible. Are

there circumstances in which sexual transmission may

be more likely? The answer to this question is based

on plausibility rather than direct evidence, but,

circumstances in which blood contact is more likely,

such as sexual contact during menstruation, involving

traumatic sexual practices and in the presence of

genital ulceration, may introduce a significant risk

of sexual transmission of hepatitis C.

And finally, but most importantly, what advice should

be given to people with hepatitis C and their sexual

partners? My advice is that for people in stable

relationships, condoms are not necessary. Although I

believe menstruation (whether the female or male

partner has hepatitis C) to be a low risk setting for

sexual transmission, either use of condoms or

abstinence from vaginal sex is probably a reasonable

policy. With regard to sexual contact with casual

partners, my advice would be that condom use is

sensible, more for protection from other truly

sexually transmissible infections.

Dr Dore, Lecturer in Epidemiology, Infectious

Diseases Physician, National Centre in HIV

Epidemiology and Clinical Research, University of New

South Wales. Abridged with thanks from the fully

referenced original in the Australian Hepatitis

Chronicle, Issue 4 March 2000: 2-5.

__________________________________________________

[Guest guest]

Sexual Transmission of Hepatitis C:

What is the Evidence? Dr. Dore

A recent article in The New England Journal of

Medicine first authored by Dr. Miriam Alter, the chief

hepatitis epidemiologist (disease transmission

researcher) from the Centers for Disease Control and

Prevention in Atlanta, GA, USA; claimed an independent

association (a linking factor, in its own right)

between hepatitis C infection and number of lifetime

sexual partners (Alter M et al. NEJM 341:556-62,

1999). It also claimed that 20-25% of all hepatitis C

infections in the United States were acquired through

sexual contact.

The study, a random household survey, involved

interviews, physical examination, and collection of

blood specimens to assess the health and nutritional

status of Americans - hepatitis C was only one of

numerous diseases evaluated. Among adults, hepatitis C

prevalence was 1.8%, with independent associations

including education level, poverty index, marijuana

use, cocaine use, number of sexual partners, and age

at first sexual intercourse. The study collected

extensive data, but failed to ask the crucial question

of " have you ever injected illicit drugs? " .

The authors were happy to acknowledge that having the

odd joint or bong was not a biologically plausible

explanation for transmission of hepatitis C, [when

saying that] " marijuana use serves as a surrogate for

other methods of transmission (such as injection-drug

use and high-risk sexual practices). " However, there

is a much more obvious form of " surrogacy " represented

by their results - it is likely that most, if not all,

of the factors associated with higher levels of

hepatitis C prevalence (poor education level, poverty,

cocaine use, increased number of sexual partners and

early age of first sexual intercourse) were also

strongly associated with injecting drug use.

In a letter responding to their article we stated that

the apparent association between hepatitis C and

number of sexual partners was an example of

epidemiological confounding [something that skews or

distorts a research study] (Dore G et al. NEJM

341:2093-4, 1999). In particular, it is likely that

people reporting a higher number of sexual partners

were, as a group, more likely to have a history of

injecting, than those who had few partners. We argued

that even in other studies where the question " have

you ever injected illicit drugs? " has been asked,

people are often not willing to answer correctly.

In an environment such as the United States, where

drug use in general, and injecting, in particular, are

highly stigmatized, it would not be surprising to see

substantial under-reporting of injecting drug use. We

also outlined the evidence against significant levels

of hepatitis C transmission through sexual contact.

So, what is the current state of evidence around

sexual transmission of hepatitis C? An examination of

this evidence is essential in order to inform a person

with hepatitis C and his or her partners about the

risk of sexual transmission, whatever that risk. On

purely biological grounds, it is plausible that

hepatitis C could be transmitted sexually. Although

semen and vaginal secretions themselves probably

contain little, if any, hepatitis C virus (Caldwell S,

et al. Liver Trans Surg 2:124-9, 1996), sexual contact

may well involve some degree of blood contact, for

example, if sex takes place during a woman's

menstruation, or involves some degree of trauma.

It is another matter altogether to demonstrate that

sexual transmission of hepatitis C actually occurs, or

if it does, that it occurs with a sufficiently high

probability to be of concern to people with hepatitis

C and their partners.

Several types of studies have been used to investigate

the sexual transmission of hepatitis C: Cases of

people diagnosed with hepatitis C, self-reporting how

they felt they contracted the condition. Although a

high proportion of cases are associated with a history

involving the potential for blood contact,

predominantly through sharing of injecting equipment,

cases without such a history may be attributed to

sexual transmission.

In the United States, 20-25% of people with acute

hepatitis C are considered to have acquired their

infection through sexual contact (Alter M and Moyer L.

J AIDS 18(suppl 1):S6-S10, 1998). Many of these people

give a history of sexual contact with a person with

hepatitis C, but deny other risk factors such as

sharing injecting equipment.

In contrast, among a series of 467 people newly

diagnosed with hepatitis C from the north coast of New

South Wales, all but one reported actual or potential

blood exposures (injecting drug use, 85%; pre-1990

blood transfusion, 6%; blood exposures, 8%). None of

the cases reported sexual contact as their only

possible exposure (Sladden T, et al. MJA 166:290-293,

1997). Of 54 partners who tested positive for

hepatitis C and were questioned about risk factors,

all had potential blood exposure. Why the disparity

between studies in the United States and Australia, in

settings where, presumably, sexual behavior and

practices are quite similar?

Under reporting of injecting drug use is the obvious

explanation. Although injecting drugs undoubtedly is

stigmatized in Australia, in the United States there

is almost certainly greater stigmatization of illicit

drug use. Hardened sentencing for drug-related crimes

in recent years, and a general mistrust of those in

authority, may have also contributed to greater under

reporting of illegal activities. In contrast, the

north coast of New South Wales is probably an area

where stigmatization of drug use is relatively low,

and trust of researchers and those in authority may be

relatively high.

Prevalence in people at sexual risk

Certain population groups are recognized as being at

higher risk of sexually transmissible infections, and

would be expected to have higher rates of hepatitis C

if it was indeed sexually transmissible. Female sex

workers and homosexual men are probably the groups

most often considered in such studies, which have

generally not found increases in the levels of

hepatitis C that would be consistent with an agent

that is readily sexually transmissible.

In a study among gay men in Sydney (Bodsworth N, et

al. Genitourin Med 72:118-22 1996), although the

prevalence of hepatitis C (7%) was considerably higher

than estimates of the general adult male population

prevalence (2%) (ANCARD 1998), there was no

association between hepatitis C and either number of

sexual partners or sexual practices. The higher rates

of injecting drug use, and not sexual behavior, among

Sydney gay men are almost certainly the explanation

for this higher hepatitis C prevalence.

Cross-sectional partner studies

Several studies over the past decade have found that

the spouses or regular sexual partners of people

diagnosed with hepatitis C have higher levels of

hepatitis C than found in the general population. The

prevalence in partners has also been found to be

related to the duration of the sexual relationship.

Such studies, based on testing at one time point, may

suggest transmission associated with stable

partnerships, but whether it is sexual contact, other

forms of contact involving blood, or a common

antecedent history such as unsterilized medical

injections in both partners is difficult to establish.

Longitudinal partner studies

The most convincing evidence for or against sexual

transmission should come from longitudinal partner

studies, in which one member of the couple is known to

have hepatitis C at the start, the other is known or

can be assumed not to be infected, and forms of blood

contact not involving sex can be convincingly

excluded. So far, very few such studies have been

reported. Two studies of the sexual partners of

several hundred women infected through contaminated

anti-D immunoglobulin injections given following

childbirth in 1977-1978, in Germany and Ireland and

with average duration of relationships of 10-15 years

found no cases of probable sexual transmission (Meisel

H et al. Lancet 345:1209-11, 1995; Power J et al.

Lancet 344:1166-7, 1994).

What does an examination of these studies deduce with

respect to sexual transmission of hepatitis C? If the

question is " can hepatitis C be transmitted through

sexual contact? " then the answer almost certainly is

yes. If the question is " what is the level of risk of

hepatitis C transmission through sexual contact? " ,

then the answer is extremely low to negligible. Are

there circumstances in which sexual transmission may

be more likely? The answer to this question is based

on plausibility rather than direct evidence, but,

circumstances in which blood contact is more likely,

such as sexual contact during menstruation, involving

traumatic sexual practices and in the presence of

genital ulceration, may introduce a significant risk

of sexual transmission of hepatitis C.

And finally, but most importantly, what advice should

be given to people with hepatitis C and their sexual

partners? My advice is that for people in stable

relationships, condoms are not necessary. Although I

believe menstruation (whether the female or male

partner has hepatitis C) to be a low risk setting for

sexual transmission, either use of condoms or

abstinence from vaginal sex is probably a reasonable

policy. With regard to sexual contact with casual

partners, my advice would be that condom use is

sensible, more for protection from other truly

sexually transmissible infections.

Dr Dore, Lecturer in Epidemiology, Infectious

Diseases Physician, National Centre in HIV

Epidemiology and Clinical Research, University of New

South Wales. Abridged with thanks from the fully

referenced original in the Australian Hepatitis

Chronicle, Issue 4 March 2000: 2-5.

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