HIV/AIDS Epi Update - May 2004

HIV Infections among MSM in Canada

Introduction

In Canada, the HIV/AIDS epidemic has had a tremendous impact on men who have sex with men (MSM). Even though the toll of the epidemic no longer affects MSM to the same extent that it did in the early to mid-1980s, this group still accounts for the largest number of reported HIV and AIDS diagnoses. Recent data on HIV incidence and risk behaviours suggest that MSM continue to be at risk for HIV infection and other sexually transmitted infections (STIs). This report updates the current information on the status of HIV and AIDS among MSM in Canada.

AIDS Surveillance Data

• As of June 30, 2003, the Centre for Infectious Disease Prevention and Control (CIDPC) reported a cumulative total of 18,934 AIDS cases. Of the 17,136 adult male AIDS cases, 77.1% were attributed to MSM and an additional 5.0% were attributed to the MSM who also reported injecting drugs (MSM/IDU).¹
• There has been a steady decrease in the proportion of adult male AIDS cases attributed to MSM that were reported to CIDPC from 1986 to 1999, from about 80% before 1996 to 54.4% in 1999. In 2000, this proportion increased to 57.4% and since then has remained fairly steady. The proportion was 53.2% in 2002.¹
• The proportion of adult AIDS cases attributed to MSM/IDU has remained relatively steady, varying between 2.7% and 6% during the last five years.¹

HIV Surveillance Data

While AIDS data provide information on HIV infection that occurred about 10 years in the past, HIV data provide a picture of more recent infections.

• Positive HIV test reports sent from each province and territory are collated and synthesized at the national level by CIDPC. These reports show that before 1998, 75.5% of positive HIV test reports among adult males were attributed to MSM. This proportion then decreased to around 48% during 1998-1999. It increased to 53.7% in 2000 and has been in the range of 48% to 52% during 2001-02.1 A similar trend is observed in the absolute number of positive HIV test reports attributed to MSM among adult males. The increase in the number and proportion of MSM among adult male positive HIV test reports noted in 2000 was the first increase seen since the 1980s.

MSM Continue to Account for the Greatest Number of Prevalent and Incident HIV Infections

The 2002 estimates of prevalence (number living with HIV) and incidence (number newly infected in a year) show that MSM continue to be the most affected group. At the end of 2002, an estimated 56,000 (46,000-66,000) people in Canada were living with HIV infection (including AIDS) and, of these, 58% or 32,500 infections occurred among MSM. The largest absolute increase in prevalent infections in 2002 was in the MSM exposure category, which had 2,900 more prevalent infections than in 1999 (10% relative increase). The combined exposure category of MSM and IDU (MSM-IDU) made up 4% of total prevalent infections in 2002.²

In 2002, MSM accounted for 40% of the estimated total of 2,800 to 5,200 new infections in Canada or approximately 1,000 to 2,000 new HIV infections. This represents a slight increase from the 38% estimated in 1999 (Figure 1).²

High Rates of New HIV Infections in Some Parts of Canada

• In the late 1990s, data from Ontario showed an increase in the rate of new HIV infections among MSM who were repeat testers for HIV, from 0.79 infections per 100 person years in 1996 to 1.39 per 100 person years in 1999. Incidence was significantly higher in Toronto and Ottawa compared with the rest of Ontario.3 In 2000, incidence appeared to have stabilized in Ontario.³ With the use of a new laboratory technique to identify recent infections among those with newly
  diagnosed HIV (STARHS assay) during 1999-2002, HIV incidence decreased among MSM in Toronto, from 4.3 per 100 person years (PY) in 1999 to 2.8 per 100 person years in 2001 and has remained fairly steady to 2002. In contrast, HIV incidence among MSM in Ottawa appeared to increase, from less than 0.1 per 100 PY in 1999 to 3.5 per 100 PY in the first half of 2001 and decreased to around 1.8 per 100 PY in 2002.⁴
• In Quebec, the Omega Cohort provides information on the incidence and psychosocial determinants of HIV infection among MSM living in Montreal. From October 1997 to August 2001, overall HIV incidence remained relatively stable, varying from 0.44 to 0.71 per 100 PY without any clear increasing or decreasing trend. However, trends in HIV incidence varied by age. The relative rates in 2001 were 2.7 among younger MSM and 1.3 among older MSM.5 From October 1996 to October 2002, the overall incidence was 0.59 per 100 PY. It increased non-significantly from 0.56 to 0.88 per 100 PY between 1997 and 2002.⁶
• In British Columbia, results from the Vanguard study, a prospective cohort of young gay and bisexual men in Vancouver, show that the annual rate of new HIV infections among those men who had never injected drugs increased from a range of 0.2-1.0 per 100 PY during 1996 to 1999 to 2.0 per 100 PY in 2000 and to 2.5 per 100 PY in the first nine months of 2001.⁷
• With respect to HIV prevalence, data (self-reported or test data) from surveys done directly among MSM showed a very high rate before 1990: 23% to 32% in Vancouver,8,9 27% to 57% in Toronto,8,10 20% to 25% in Montreal8,¹¹ and between 10% and 20% in other regions of Canada.⁷ By 1998/2000, it appeared that there was some decline in the HIV prevalence rate among MSM surveyed by similar methods: 16% in Vancouver12,13 and 10%-16% in Montreal.^14,15 A 2002 survey in British Columbia reported an overall prevalence of 12.9% with a higher proportion of HIV-positive men being residents of Vancouver.16 However, a high prevalence rate is still seen among MSM who are also IDU, for example, 14% to 22% among MSM/IDU attending needle exchange programs in Quebec (1995-2000).^17,18
• The Omega Cohort results showed that HIV prevalence increased with age from a rate of 0.0% in MSM under 20 years to 3.1% in those aged 40-44 years, and then decreased to 0.4% among those 45 years of age or over. However, this trend was not statistically significant.⁵

Figure 1. Distribution (%) of new HIV infections among MSM, by time period

Continuing Risk Behaviour among MSM

Recent data on risk behaviours suggest that MSM continue to be at considerable risk of HIV infection and other STIs through engaging in unprotected receptive or insertive anal intercourse (UAI) with casual or regular partners, or practising unsafe sex (oral or anal) with a known HIV-positive partner:

• It is estimated that around 15% of  Montreal's MSM  are currently  HIV-infected. Results from the Montreal Omega Cohort Study indicate that 12% of MSM practise UAI with casual partners. This could result in a significant increase in the risk of new HIV infections.¹⁹ From 1997 to 2002, risky anal sex (RAS) increased slightly from 16% to 19%, and UAI increased slightly from 34% to 39%. The increases in risky behaviour, though slight, need to be closely monitored and better understood in order to ascertain their possible impact on HIV incidence.⁶
• In another survey in Montreal, the prevalence of reported UAI was 12% among MSM recruited in bars or saunas but was up to 21% to 24% among MSM who were HIV-positive.¹⁴ A study on sexual risk behaviours of HIV-positive MSM in Montreal found that 15% had had unprotected insertive anal sex with an HIV-negative partner or a partner whose serostatus was unknown^.15
• With respect to relapse to risky behaviours, available data indicate that 10% of the Montreal cohort and 26% to 30% of the Vancouver cohort who reported safe sex at baseline disclosed relapse to unprotected anal sex at follow-up six to 12 months later.^20,21
• A 2002 survey of MSM in BC found that the majority of participants generally reported practising safe sex (73.4%). However, those with multiple partners reported a 25% increase in UAI, from 18.8% in 2000 to 23.5% in 2002. It also showed that at least 27% of participants had had unprotected sex with a partner of unknown serostatus in the previous year.¹⁶
• Between May 1995 and September 2001, participants aged 15 to 35 years in a cohort study of MSM in the Greater Vancouver region reported increasing unprotected insertive (relative risk: 3.5) and receptive (relative risk: 5.1) anal sex with an HIV-positive partner; this increase were associated with high-risk sex. For men in Montreal, having a casual partner (OR: 3.0) and having at least two regular partners in the previous year (OR: 3.0) were independently associated with high-risk sexual behaviour.²⁴
• The results of a cohort study of MSM aged 15 to 35 enrolled in the Vanguard Project in Vancouver showed that the proportion of MSM reporting insertive UAI with casual partners increased significantly, from 17% in 1997-98 to 22% in 2001-02, and the proportion of MSM who reported receptive UAI increased from 11% to 16% during the same period.²⁵ There was an increase in both receptive and insertive UAI with a regular partner, although it was not statistically significant. There was, however, no significant change in HIV seroconversion rate during this period (1997-2002). This study also reported that most of the MSM who engaged in UAI reportedly did so with sero-concordant partners, although sero-concordant receptive UAI was reported by 12%.²⁵ In the same cohort study in Vancouver, a significant increase was observed in the proportion of MSM reporting recent use of crystal meth, ecstasy, and marijuana; the use of poppers, marijuana, hallucinogens, crystal meth, and ecstasy was found to be associated with receptive UAI with casual partners.²⁶
• STI data may be used as a marker for unsafe sexual behaviour. A review of the gonorrhea surveillance data in Canada reveals that reported cases of gonorrhoea among men increased by 53% between 1997 and 2001, the most dramatic increase (68%) being seen among those aged 30 to 39 years.27 Despite the limitations of the data in assessing the sexual orientation of the reported cases, it is estimated that less than 4% of male cases from 1994 to 2001 are MSM-associated.²⁸ In an analysis of a syphilis outbreak among MSM in Calgary, Alberta, in 2000-2001, it was reported that 35.7% of the MSM cases were co-infected with HIV.28 The reported high rate of HIV in UAI was associated with seroconversion.
• Data from the Vancouver cohort and the Montreal cohort were combined and analyzed, comparing  the sexual behaviours of HIVpositive and HIVnegative gay and bisexual men aged 16 to 30 years. Results show that 56% of HIV-positive men and 40% of HIV-negative men reported having engaged in receptive UAI during the previous six months or year.23 More recently, high-risk behaviour among MSM in both cities was associated with nitrite inhalant use and sex in public and commercial sex venues. Independent determinants of risk-taking for men in both cities were the use of poppers (Vancouver: odds ratio [OR] 2.1, Montreal: OR 2.9) and having sex in a bathhouse (Vancouver: OR 1.9, Montreal OR 1.8). In Vancouver, having sex in a bar (OR: 1.8) and having at least 20 casual partners in the previous year (OR: 1.7)  co-infection, the syphilis outbreak itself and the increase in gonorrhea cases further support the suggestion of an increase in unprotected sexual encounters among MSM.

Comment

A number of biases must be taken into account when interpreting the results noted here. HIV diagnostic data are limited to persons who present themselves for testing, and so trends in these numbers may be influenced by testing patterns or improved ability to remove duplicate tests. In addition, identifying information that accompanies HIV testing data is sometimes incomplete or inaccurate, and this may limit the usefulness of HIV incidence estimates. Results of cohort studies are limited by selection biases, loss to follow-up and problems with generalizability.

Despite these limitations, available data suggest that there was an increase nationally in new HIV infections among MSM in the late 1990s, and although this increase may not have continued, overall incidence does not appear to have decreased since then. There is also a continued presence of high-risk behaviours among MSM across the country. This high-risk behaviour among MSM is also noted elsewhere. For example, increases have been seen for HIV-associated risk behaviours and/or STDs among MSM in the USA,^29-31 Amsterdam³² and Sydney, Australia.³³

Several hypotheses might explain these increases in HIV-associated risk behaviours, including feelings of complacency or optimism related to the success of antiretroviral therapy,²⁷ false reassurance upon learning an HIV-negative result, a lack of direct experience of the AIDS epidemic in the younger generation of gay men, a desire to escape the rigorous norms and standards required for a lifetime of safe sex,^34-36 alcohol/drug use^24,36-38 and the impact of Internet chat rooms as a risky environment.39

The increase in new infections among MSM and the number of MSM living with HIV underscore the need for innovative prevention programs to reduce the spread of HIV and STIs among the gay community. These programs should not only focus on those who are not yet infected but also those who are HIV positive. National risk behaviour measured over time and in different settings that reflect urban as well as rural areas would be useful to better characterize the epidemic among MSM and to support effective prevention and care programs.

References

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