HIV/AIDS Epi Update - May 2004

HIV and AIDS among Women in Canada

Introduction

At A Glance

In Canada, a total of 1,555 AIDS cases and 7,256 HIV cases have been reported in adult women up to June 30, 2003.

Women represent an increasing proportion of those with positive HIV test reports in Canada and in 2002 accounted for 25% of all positive HIV test reports.

Heterosexual contact and injecting drug use are the two major risk factors for HIV infection in women.

The HIV/AIDS epidemic in Canada has changed from the early epidemic, which affected primarily men who have sex with men (MSM), to the current epidemic, which increasingly affects other groups such as injecting drug users (IDU) and heterosexuals. As a result, the number and percentage of women living with HIV/AIDS is increasing. The HIV/AIDS epidemic among women is of particular concern because of the potential for transmission to their infants. This report updates the status of HIV and AIDS among adult and adolescent women (15 years and older) in Canada up to June 30, 2003.

AIDS Surveillance Data

In Canada, of the 18,713 cumulative AIDS cases in adults reported up to June 30, 2003, to the Centre for Infectious Disease Prevention and Control (CIDPC), 1,555 (8.3%) were women. The proportion of all reported adult AIDS cases (for which gender and age are known) occurring in women has increased over time, from 6.1% before 1994 to 15.8% in 1999; in 2002, the proportion was 16.5%.¹

Of all cumulative reported AIDS cases in women up to June 30, 2003, 67.9% were attributed to heterosexual contact,* 23.3% to injecting drug use and 8.5% to recipients of blood or blood products. The proportion of adult female AIDS cases attributed to IDU increased from 20.1% before 1998 to 46.2% in 1998 and has since dropped to 29.3% in 2002.¹

HIV Surveillance Data

AIDS data can contribute to an understanding of trends in HIV infections but only on infections acquired approximately 10 years in the past. In contrast, positive HIV test reports provide a picture of more recent infections. Data from provincial and territorial HIV testing programs indicate that a total of 7,256 positive HIV test reports with known age and gender have been reported in adult women up to June 30, 2003.¹

Women account for a growing proportion of positive HIV tests reports with known age and gender among adults in Canada. The proportion of females each year has risen, from 12% in the years between 1985 and 1997 to nearly 25% of adult positive HIV test reports between January 1999 and December 31, 2001. In 2002, this proportion increased slightly to 25.4%. The proportion of women among positive HIV test reports varies considerably by their age and is highest among adolescents and young adults. In 2001, women accounted for 44.4% of positive HIV test reports among those aged 15 to 29 years, an increase from 42% in 2000. In 2002, this proportion decreased slightly to 38.6% (Figure 1).¹

Figure 1. Proportion of positive HIV test reports among women by age group and year of test (1985-2002)

Among women, the primary exposure categories associated with newly diagnosed HIV infection are heterosexual contact and IDU (Table 1). The proportion of positive HIV test reports in women attributed to heterosexual contact has increased over time, from 46.2% for the period 1985-1997 to 62.5% in 2001. In 2002, this proportion decreased slightly to 58.3%. The proportion attributed to IDU varied between 33% and 48% during this period, with the suggestion of a slight decrease over time (Table 1).

Heterosexual contact still remains the main risk factor for HIV infection in women, although injecting drug use is also a significant risk factor and in some studies this risk is greater among female than male IDU.²

HIV Prevalence and Incidence Estimates Show More Women Are Living with HIV/AIDS

The national HIV prevalence (total number living with HIV) estimates indicate that the number of women in Canada living with HIV, including those with AIDS, continues to grow. By the end of 2002, an estimated 7,700 (6,500-9,000) women were living with HIV, accounting for about 14% of the national total. This represents an increase of 13% from the 6,800 estimated at the end of 1999.³

Data from positive HIV test reports do not provide the complete picture of the annual number of new HIV infections, since only a proportion of those newly infected are tested in the same year. Furthermore, not all HIV tests reported in a given year are from cases infected in that year. The estimated number of new infections (incidence) among women continues at approximately the same rate as three years ago. In 2002, women represented 23% of all new HIV infections or an estimated 600 to 1,200 out of the total of 2,800 to 5,200 new infections in Canada. With respect to exposure category distribution among newly infected women, a slightly higher proportion was attributed to the heterosexual category in 2002 compared with 1999 (53% versus 46% respectively). The remainder of new infections among women was attributed to IDU (Figure 2).³

Figure 2. Estimated exposure category distribution (%) of new HIV infections among women by time period.

HIV among Pregnant Women and Women of Childbearing Age

HIV testing during pregnancy is an option available to women across Canada. However, physician guidelines and/or recommendations encouraging informed decisions regarding HIV testing during pregnancy vary by province and territory. These are discussed in detail in the Epi Update entitled "Perinatal Transmission of HIV," May 2004.

HIV prevalence studies among pregnant women can provide an important source of information on the prevalence rate of HIV in the general heterosexual population. Prenatal seroprevalence studies in Canada report an estimated national rate of HIV infection among pregnant women of 3-4/10,000 population.

Anonymous, unlinked seroprevalence studies across the country show that large metropolitan areas report higher rates of HIV infection among pregnant women (4.7 for Vancouver versus 3.4 for the rest of B.C. in 1994⁴; 15.3 for Montreal versus 5.2 for the province of Quebec in 1990⁵). Even provinces without large metropolitan areas have indicated significant rates (for example, 4.1/10,000 in New Brunswick for 1994-96⁶). Data from Manitoba suggest an increasing trend of HIV infection among women of childbearing age, from 0.7/10,000 in 1991 to 3.2/10,000 in 1994-95.⁷ An ongoing study among pregnant Aboriginal women in B.C. reported an HIV prevalence rate of 31.3 per 10,000 pregnancies in 2000-2002 (JD Martin, Programs Medical Officer, Pacific Region, First Nations and Inuit Health Branch, Health Canada, and A Jin, consultant for the BC First Nations Chiefs' Health Committee: personal communication).

The Alberta universal prenatal HIV screening program (in which all pregnant women are tested unless they opt out) reported an HIV infection rate of 3.3/10,000 pregnancies in 2000.⁸ An ongoing HIV seroprevalence study of pregnant women in Ontario reported a rate of 3.7/10,000.⁹ This rate is based on pregnant women who volunteered for testing (approximately 70%) whereas the rates in the other provinces (except Alberta) are based on complete samples from unlinked anonymous studies.

Risky behaviours among women, such as unsafe sex and injecting drug use, continue to put women at an increased risk of HIV. An ongoing study involving IDU in different areas across Canada found that, in 2003, about 40% of female IDU reported engaging in commercial sex work. It also showed that about 92% always used condoms with their male client partners, but almost a third never used condoms with their casual partners and condom use was infrequent with their regular partners.¹⁰

Comment

Women in Canada, especially IDU and women with high-risk sexual partners, are increasingly becoming infected with HIV. Even though the rate of new HIV infections among women is similar to three years ago, this number is still unacceptably high. The prevalence estimates indicate that more women are living with HIV in 2002 compared with 1999, and this has implications for prevention and care programs. Efforts to reduce transmission of HIV among women will need to focus not only on promoting safer sexual behaviours and reducing substance abuse but also on the intersection between the two and the underlying factors that put women at an increased risk of HIV infection.

All women, and especially women of childbearing age, should have access to HIV testing, counselling and care. More enhanced data on the trends, risk factors and geographic differences of HIV among Canadian women are needed to help target prevention and care programs.

References

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   HIV and AIDS in Canada. Surveillance report to June 30, 2003. Surveillance and Risk Assessment Division, Centre for Infectious Disease Prevention and Control, Health Canada, 2003.
2. Spittal PM, Craib KJP, Wood E et al.
   Risk factors for elevated HIV incidence rates among female injection drug users in Vancouver. Can Med Assoc J 2002; 166(7):894-99.
3. Geduld J, Gatali M, Remis R, Archibald CP.
   Estimates of HIV prevalence and incidence in Canada, 2002. CCDR 2003; 29:197-206.
4. Pi D, Ballem PJ, Schechter MT.
   The B.C. Prenatal Study: 1989-94. Final report to Health Canada, January 1995.
5. Hankins C, Hum L, Tran T et al.
   HIV seroprevalence in women giving birth to live infants in Northern Quebec (1989-93). Can J Infect Dis 1995; 6(Suppl):B:39 (Abstract 314).
6. Getty G, Leighton P, Mureika R et al.
   NB antenatal seroprevalence study. Can J Infect Dis 1997;8:24A(Abstract 205).
7. Blanchard J, Hammond G, Fast M et al.
   HIV serovalence among antenatal women in Manitoba: August, 1994 through August, 1995. Final report to Health Canada, 1996.
8. Jayaraman GC, Preiksaitis JK, Larke B.
   Mandatory reporting of HIV infection and opt-out prenatal screening for HIV infection: effect on testing rates. Can Med Assoc J 2003;168(6).
9. Remis SR, Swantee C, Major Cl et al.
   Increasing HIV testing of pregnant women in Ontario: results from the HIV seroprevalence study to September 2002. Can J Infect Dis 2003;14(Suppl A):79 (Abstract 322).
10. Health Canada.
    I-Track: enhanced surveillance of risk behaviours among injecting drug users in Canada. Pilot survey report, February 2004.
    Surveillance and Risk Assessment Division, Centre for Infectious Disease Prevention and Control, Health Canada, 2004.

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