CATIE News – Montreal researchers study HIV transmission
In an attempt to reduce the spread of HIV, safer-sex techniques were developed by community groups in the mid-to-late 1980s. The diffusion of knowledge about safer sex around the world should, in theory, have helped stop the spread of HIV. However, HIV continues to be transmitted at a relatively high rate in many parts of the globe, particularly in low- and middle-income regions, where there are tens of millions of people with HIV/AIDS. By contrast, in the high-income regions of North America, Western Europe and Australia, HIV is spreading at lower rates and fewer people are becoming infected.
The Public Health Agency of Canada estimates that there are about 58,000 HIV positive people living in Canada. It also estimates that there are at least 2,500 new HIV infections in this country every year. If this trend remains unchecked, that would mean that in 10 years there would be 25,000 additional people living with HIV in Canada.
Studying and engaging with populations at high risk for HIV infection is a first step toward reaching the goal of slowing the spread of this epidemic. The underlying factors that drive the continuing transmission of HIV in Canada in 2007 are not completely clear and are likely to be different in key populations affected by HIV, as follows:
* men who have sex with men (MSM)
* injection drug users
* Aboriginal people
* women
* immigrants from regions where HIV is common
* prisoners
* young people
To try to get a better understanding of HIV transmission, a research team in Montreal focused on the sexual behaviours of MSM in a project called the Omega Study Cohort. The team enrolled more than 1,800 HIV negative men and monitored them for up to seven years. Regular interviews and blood tests were part of this monitoring. They found that participating in unprotected receptive anal sex was the behaviour most associated with becoming HIV positive. Further details about other behaviours and transmission risks appear later in this article.
Study details
Between October 1996 and July 2003, researchers enrolled 1,846 HIV negative men who identified themselves as MSM. Their average profile was as follows:
* age – 30 years
* 75% were single
* 20% were unemployed
* 67% had continued their education beyond high school
* 50% had an annual income less than $20,000
* a history of sexually transmitted infections was common
Results—focus on behaviours
During the first six months of the study, about 40% of participants had more than two regular sex partners and one-third reported more than five sex partners.
About 40% of participants engaged in unprotected anal sex during the first six months of the study. This practice was most common among men who had sex with other HIV negative men.
HIV transmission
A total of 32 men became HIV positive (seroconverted) during the course of the study.
Based on information collected during interviews, the study team found that different practices were associated with a different risk for becoming HIV positive. Below are some of these practices as well as the risks of seroconversion associated with them.
Number of partners
Having unsafe sex with multiple sexual partners increases the risk that a person will be exposed to sexually transmitted infections, including HIV. So, determining the number of sex partners is sometimes useful in calculating risks for acquiring HIV infection. The study team found the following:
* Having between six and 49 sexual partners in the six months prior to seroconversion doubled the risk of becoming HIV positive.
* Having 50 or more sex partners in the six months prior to seroconversion was associated with a five-fold risk of seroconversion.
Focus on anal sex
In the Montreal study, the main risk factor for HIV transmission was unprotected anal sex between men—one who was HIV negative and the other who was either HIV positive or whose HIV status was not known. Below are the risks associated with practicing anal receptive and anal insertive sex:
* The men at greatest risk for HIV infection were those who practiced receptive anal intercourse. Their risk for seroconversion was 12 times greater than that of men who did not practice anal sex at all or men who did not have anal sex with an HIV positive person.
* Men who engaged in both unprotected insertive and receptive anal sex were 8 times more likely to get HIV than men who did not practice anal sex with an HIV positive partner.
* Men who only practiced unprotected insertive anal sex had a five-fold risk of becoming HIV positive.
Hidden behaviour?
An interesting finding from the Montreal study: Some HIV negative men who claimed to always practice protected anal sex with partners who were HIV positive or whose serostatus was unknown eventually became HIV positive. The study team suggested several possibilities to explain this seemingly contradictory information:
* Condoms can break. Even among people who regularly use condoms, the risk of what the Montreal team called “condom failure” ranges between 5% and 10%.
* Condoms may not work at blocking HIV infection if they are used only to prevent exposure to ejaculation after first having brief, unprotected intercourse.
* Because of the stigma of engaging in unprotected intercourse, some study participants may not have correctly disclosed their sexual behaviours.
Oral sex
Based on a review of data from other studies, the Montreal team noted that HIV can be transmitted through oral sex but the risk of this is very low. In the Omega Study, engaging in unprotected oral receptive sex with an HIV positive partner doubled the risk of becoming HIV positive. However, the study team cautioned that some of the men who claimed to have been infected as a result of oral sex could have been infected because of unprotected anal sex that they neglected to disclose. Another point to consider is that because a relatively small number of seroconversions occurred in the Omega Study, the reliability of conclusions drawn about oral sex and HIV transmission is very limited.
Key points
In this study, researchers confirmed that “unprotected receptive anal sex was the most important risk factor” for transmitting HIV infection.
In general, researchers also noted that condoms are of “significant value in reducing HIV transmission.” However, the use of condoms for sex between serodiscordant partners (one is HIV negative and the other HIV positive) does not, according to their study results, provide complete protection against HIV infection.
The practice of having sex with people of the same HIV serostatus is called serosorting. The Montreal study team suggested that serosorting appears to be an “acceptable compromise between obtaining sexual fulfillment and the adoption of effective HIV prevention practices.”
Although the number of men who seroconverted in the Omega Study is relatively low, the study team stated that “this rate translates into several hundred new HIV infections each year.” This is outcome is disquieting.
Perhaps a useful outcome of the Omega Study might be to conduct further research that can strengthen HIV prevention programs, enable greater use of condoms and reduce “condom failure,” at least among MSM. Such efforts would be appreciated not just in Canada but in other high-income countries where HIV continues to spread.
The funding for the Omega Study Cohort was provided by the following agencies:
* Health Canada
* CIHR—Canadian Institutes of Health Research
* FRSQ—Fonds de la recherché en santé du Québec
—Sean R. Hosein
REFERENCES:
1. Public Health Agency of Canada. HIV/AIDS Epi Updates, August 2006, Surveillance and Risk Assessment Division, Centre for Infectious Disease Prevention and Control, Public Health Agency of Canada, 2006.
2. Lavoie E, Alary M, Remis R, et al. Determinants of HIV seroconversion among men who have sex with men living in a low HIV incidence population in the era of highly active antiretroviral therapies. Sexually Transmitted Diseases 2007; in press.
3. Buchbinder SP, Vittinghoff E, Heagerty PJ, et al. Sexual risk, nitrite inhalant use, and lack of circumcision associated with HIV seroconversion in men who have sex with men in the United States. Journal of Acquired Immune Deficiency Syndromes 2005 May 1;39(1):82-9.
4. Monno L, Carbonara S, Ciracì E, et al. Twenty years later: the recent trends of HIV-infection—evidence from an Italian region. Infection 2007; in press.
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CATIE News - Montreal researchers study HIV transmission
From: maiser@mercury.catie.ca on behalf of CATIE Info (info@catie.ca)
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Sent: November 12, 2007 4:41:06 PM
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CATIE News – Montreal researchers study HIV transmission
In an attempt to reduce the spread of HIV, safer-sex techniques were developed by community groups in the mid-to-late 1980s. The diffusion of knowledge about safer sex around the world should, in theory, have helped stop the spread of HIV. However, HIV continues to be transmitted at a relatively high rate in many parts of the globe, particularly in low- and middle-income regions, where there are tens of millions of people with HIV/AIDS. By contrast, in the high-income regions of North America, Western Europe and Australia, HIV is spreading at lower rates and fewer people are becoming infected.
The Public Health Agency of Canada estimates that there are about 58,000 HIV positive people living in Canada. It also estimates that there are at least 2,500 new HIV infections in this country every year. If this trend remains unchecked, that would mean that in 10 years there would be 25,000 additional people living with HIV in Canada.
Studying and engaging with populations at high risk for HIV infection is a first step toward reaching the goal of slowing the spread of this epidemic. The underlying factors that drive the continuing transmission of HIV in Canada in 2007 are not completely clear and are likely to be different in key populations affected by HIV, as follows:
* men who have sex with men (MSM)
* injection drug users
* Aboriginal people
* women
* immigrants from regions where HIV is common
* prisoners
* young people
To try to get a better understanding of HIV transmission, a research team in Montreal focused on the sexual behaviours of MSM in a project called the Omega Study Cohort. The team enrolled more than 1,800 HIV negative men and monitored them for up to seven years. Regular interviews and blood tests were part of this monitoring. They found that participating in unprotected receptive anal sex was the behaviour most associated with becoming HIV positive. Further details about other behaviours and transmission risks appear later in this article.
Study details
Between October 1996 and July 2003, researchers enrolled 1,846 HIV negative men who identified themselves as MSM. Their average profile was as follows:
* age – 30 years
* 75% were single
* 20% were unemployed
* 67% had continued their education beyond high school
* 50% had an annual income less than $20,000
* a history of sexually transmitted infections was common
Results—focus on behaviours
During the first six months of the study, about 40% of participants had more than two regular sex partners and one-third reported more than five sex partners.
About 40% of participants engaged in unprotected anal sex during the first six months of the study. This practice was most common among men who had sex with other HIV negative men.
HIV transmission
A total of 32 men became HIV positive (seroconverted) during the course of the study.
Based on information collected during interviews, the study team found that different practices were associated with a different risk for becoming HIV positive. Below are some of these practices as well as the risks of seroconversion associated with them.
Number of partners
Having unsafe sex with multiple sexual partners increases the risk that a person will be exposed to sexually transmitted infections, including HIV. So, determining the number of sex partners is sometimes useful in calculating risks for acquiring HIV infection. The study team found the following:
* Having between six and 49 sexual partners in the six months prior to seroconversion doubled the risk of becoming HIV positive.
* Having 50 or more sex partners in the six months prior to seroconversion was associated with a five-fold risk of seroconversion.
Focus on anal sex
In the Montreal study, the main risk factor for HIV transmission was unprotected anal sex between men—one who was HIV negative and the other who was either HIV positive or whose HIV status was not known. Below are the risks associated with practicing anal receptive and anal insertive sex:
* The men at greatest risk for HIV infection were those who practiced receptive anal intercourse. Their risk for seroconversion was 12 times greater than that of men who did not practice anal sex at all or men who did not have anal sex with an HIV positive person.
* Men who engaged in both unprotected insertive and receptive anal sex were 8 times more likely to get HIV than men who did not practice anal sex with an HIV positive partner.
* Men who only practiced unprotected insertive anal sex had a five-fold risk of becoming HIV positive.
Hidden behaviour?
An interesting finding from the Montreal study: Some HIV negative men who claimed to always practice protected anal sex with partners who were HIV positive or whose serostatus was unknown eventually became HIV positive. The study team suggested several possibilities to explain this seemingly contradictory information:
* Condoms can break. Even among people who regularly use condoms, the risk of what the Montreal team called “condom failure” ranges between 5% and 10%.
* Condoms may not work at blocking HIV infection if they are used only to prevent exposure to ejaculation after first having brief, unprotected intercourse.
* Because of the stigma of engaging in unprotected intercourse, some study participants may not have correctly disclosed their sexual behaviours.
Oral sex
Based on a review of data from other studies, the Montreal team noted that HIV can be transmitted through oral sex but the risk of this is very low. In the Omega Study, engaging in unprotected oral receptive sex with an HIV positive partner doubled the risk of becoming HIV positive. However, the study team cautioned that some of the men who claimed to have been infected as a result of oral sex could have been infected because of unprotected anal sex that they neglected to disclose. Another point to consider is that because a relatively small number of seroconversions occurred in the Omega Study, the reliability of conclusions drawn about oral sex and HIV transmission is very limited.
Key points
In this study, researchers confirmed that “unprotected receptive anal sex was the most important risk factor” for transmitting HIV infection.
In general, researchers also noted that condoms are of “significant value in reducing HIV transmission.” However, the use of condoms for sex between serodiscordant partners (one is HIV negative and the other HIV positive) does not, according to their study results, provide complete protection against HIV infection.
The practice of having sex with people of the same HIV serostatus is called serosorting. The Montreal study team suggested that serosorting appears to be an “acceptable compromise between obtaining sexual fulfillment and the adoption of effective HIV prevention practices.”
Although the number of men who seroconverted in the Omega Study is relatively low, the study team stated that “this rate translates into several hundred new HIV infections each year.” This is outcome is disquieting.
Perhaps a useful outcome of the Omega Study might be to conduct further research that can strengthen HIV prevention programs, enable greater use of condoms and reduce “condom failure,” at least among MSM. Such efforts would be appreciated not just in Canada but in other high-income countries where HIV continues to spread.
The funding for the Omega Study Cohort was provided by the following agencies:
* Health Canada
* CIHR—Canadian Institutes of Health Research
* FRSQ—Fonds de la recherché en santé du Québec
—Sean R. Hosein
REFERENCES:
1. Public Health Agency of Canada. HIV/AIDS Epi Updates, August 2006, Surveillance and Risk Assessment Division, Centre for Infectious Disease Prevention and Control, Public Health Agency of Canada, 2006.
2. Lavoie E, Alary M, Remis R, et al. Determinants of HIV seroconversion among men who have sex with men living in a low HIV incidence population in the era of highly active antiretroviral therapies. Sexually Transmitted Diseases 2007; in press.
3. Buchbinder SP, Vittinghoff E, Heagerty PJ, et al. Sexual risk, nitrite inhalant use, and lack of circumcision associated with HIV seroconversion in men who have sex with men in the United States. Journal of Acquired Immune Deficiency Syndromes 2005 May 1;39(1):82-9.
4. Monno L, Carbonara S, Ciracì E, et al. Twenty years later: the recent trends of HIV-infection—evidence from an Italian region. Infection 2007; in press.
To see a directory of archived messages, visit CATIE's Web site at http://www.catie.ca/catienews.nsf
CATIE-News is written by Sean Hosein, with the collaboration of other members of the Canadian AIDS Treatment Information Exchange, in Toronto. Your comments are welcome.
Permission to Reproduce:
This document is copyrighted by the Canadian AIDS Treatment Information Exchange (CATIE). All CATIE materials may be reprinted and/or distributed without prior permission. However, reprints may not be edited and must include the following text:
From Canadian AIDS Treatment Information Exchange (CATIE). For more information visit CATIE's Information Network at http://www.catie.ca
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