Understanding Sexually Transmitted Infections (STI):The

Canadian Context

Alexander McKay, Ph.D.Research Coordinator

The Sex Information & Education Council of Canada

(SIECCAN)

Understanding Sexually Transmitted Infections (STI): The Canadian Context

• Topics• Understanding STI: The basics• Chlamydia: The most important STI?• HIV in Canada• Effectiveness of condoms for STI

prevention• Sexual behaviour of Canadian young

people and obstacles to condom use

Sexually Transmitted Infections

Basic but commonly misunderstood information

The 5 Most Common STIs in Canada Are:

• 1. Human papillomavirus (HPV)

• 2. Herpes Simplex Virus (HSV)

• 3 Chlamydia

• 4. Gonorrhea

How Common are STI in Canada?

• HPV: At least 50% of sexually active males and females will have an HPV infection at some point in their lives. Up to 80% of women will have been infected by HPV by age 50.

• HSV-2: About 25% of women and 13% of men have an HSV-2 infection.

• Chlamydia: About 4% to 6% of women aged 15-24 have an active Chlamydia infection.

Most Cases of STI are Asymptomatic (no visible signs or symptoms)

• HPV – 80%+

• HSV-2 – 60%

• Chlamydia – men 50%, women 70%+

Bacterial Versus Viral STI

• Bacterial• Chlamydia• Gonorrhea• Syphilis• Chancroid

• Viral• HIV• HPV• HSV• Hepatitis B• Cytomegalovirus

Reportable Versus Non-Reportable STIReportable = cases reported to Provincial Ministries of

Health/Public Health Agency of Canada

• Reportable STI• Chlamydia• Gonorrhea• Syphilis• HIV

• Non-Reportable• HPV• HSV

Three Ways the Occurrence of STIs is Described: Rates, Incidence, & Prevalence

• STI Rates: The number of reported cases per 100,000 of the population.

• STI Incidence: The frequency with which an STI appears in the population.

• STI Prevalence: The proportion of individuals in a population having a STI at a given time.

STI Statistics in Perspective

• Ongoing data from public health agencies involves the reportable STIs and gives us a rate based on the number of reported cases.

• Most media reports on trends in STI in Canada concern reported rates and often assume that an increase in reported rates must mean that actual prevalence is also increasing.

• Is this true? (Chlamydia as a case study)

Chlamydia:

Canada’s Most Important STI?

Chlamydia: Key Facts

• In 2004 there were 31,109 positive Chlamydia tests for females aged 15-24 reported to the Public Health Agency of Canada.

• The actual number of cases is much larger than the number of reported cases because many, if not most cases, are never diagnosed.

• Based on the limited available data, we can speculate that about 4% to 6% of Canadian women aged 15-24 are currently infected with Chlamydia.

Chlamydia: Key Facts

• Females are disproportionately infected and affected

• Up to 50% of male and 70% of female cases are asymptomatic

• Asymptomatic carriers are the main reservoir of transmission

• Consistent condom use significantly reduces Chlamydia transmission

Chlamydia: Key Facts

• In 10% - 40% of cases in females, Chlamydia results in Pelvic Inflammatory Disease (PID)

• In 20% of cases, PID results in infertility

• In 18% of cases, PID results in Chronic Pelvic Pain

• PID is a leading cause of Ectopic pregnancy

Reported Genital Chlamydia Rates Per 100,000, Canada, 1991-2004

0200400600800

100012001400160018002000

Female 15-19Male 15-19Female 10-14Male 10-14

Trends in Canadian Teen Pregnancy and Chlamydia Rates, 1991-2003

0200400600800

100012001400160018002000

P Rate (per 10,000) C Rate (per 100,000)

Chlamydia — Rates: Total and by sex: United States, 1986–2005

Note: As of January 2000, all 50 states and the District of Columbia had regulations requiring the reporting of chlamydia cases.

Rate (per 100,000 population)

MenWomenTotal

0

100

200

300

400

500

1986 88 90 92 94 96 98 2000 02 04

Chlamydia — Median state-specific positivity among 15- to 24-year-old womentested in family planning clinics, 1997–2005

Median state-specific positivity rate

0

2

4

6

8

10

1997 98 99 2000 01 02 03 04 05

Note: As of 1997, all 10 Health and Human Services (HHS) regions, representing all 50 states, the District of Columbia, and outlying areas, reported chlamydia positivity data.

Factors Influencing Reported Chlamydia Rates

• 1. Reported STI rates are affected by the number of tests done. If the number of tests increases the number of positive cases will also increase. (Urine as opposed to swab)

• 2. Increasingly sensitive tests (NAAT) increase the number of positive test results.

Chlamydia: What Do We Know?

• 1. Although reported rates of Chlamydia have been increasing steadily since 1997, it is very likely that the actual prevalence of Chlamydia has remained comparatively stable.

• 2. With an estimated prevalence of 4%-6% among 15-24 year-old women, Chlamydia is a major, but preventable, threat to the reproductive health of Canadian young people.

• 3. Prevalence of Chlamydia is much higher in socio-economically disadvantaged youth and communities.

HIV/AIDS in Canada (HIV/AIDS Epi Update; Public Health Agency of Canada)

• As of the end of 2005, there were 58,000 people living with HIV in Canada.

• Of these 58,000 HIV+ people, 15,800 (27%) were unaware of their infection.

• An estimated 2,300 to 4,500 new infections occurred in 2005 compared to 2,100 to 4,000 in 2002.

HIV/AIDS in Canada (HIVAIDS Epi Update: Public Health Agency of Canada)

• Increasing proportions of HIV infections are among women (27.8% in 2006) and this proportion is growing.

• Aboriginal people, especially women, are over-represented in the HIV epidemic in Canada.

HIV/AIDS in Canada (HIV/AIDS Epi Update: Public Health Agency of Canada)

Estimated Exposure Category Distributions (%) of New HIV Infections

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

MSN IDU Het/NE Het/E

1999

2002

2005

Preventing STI Through Enhanced Condom Use

• How effective are condoms in preventing STI?

• Is condom use increasing among Canadian young people?

• What are the behavioural obstacles to consistent condom use among young people?

How Effective are Condoms in Reducing the Risk of STI Transmission?

• Studies suggest that consistent condom use may reduce the risk of STI transmission by:

• 80% for HIV

• 60% for Chlamydia

• 90% for Gonorrhea

• 70% for HPV• Increasing condom use = lower risk for HSV-2

Condom Use and Public Health

• Promoting consistent condom use is the single most important and powerful tool in reducing the burden of STI infection on the Canadian population

• Intervention evaluation studies have clearly demonstrated that well designed educational programs can increase consistent condom use

• Sexual Behaviour of Canadian Young People and Behavioural Obstacles to Condom Use

Canadian Youth, Sexual Health and HIV/AIDS Study

Percentage of Canadian Grade 9 and 11 Students Who Have Had Intercourse At Least Once, 1989, 2002

05

101520253035404550

Grade9/Female

Grade11/Female

Grade9/Male

Grade11/Male

19892002

Average Age of First Intercourse: 2003 Canadian Community Health Survey

16.5 Years

0 5 10 15 20

Males 16.5

Females 16.5Females

Males

Canadian Youth, Sexual Health and HIV/AIDS StudyNumber of Sexual Partners Among Grade 11 Students

Who Have Ever Had Intercourse, 1989, 2002 (%)

0

10

20

30

40

50

60

Male 1989 Male 2002 Female 1989 Female 2002

123 to 56+

B.C. Adolescent Health Survey 2003 (McCreary Centre Society) Condom Use at Last

Intercourse, 1998 & 2003

52%

54%

56%

58%

60%

62%

64%

66%

68%

70%

1998 2003

condom at lastintercourse

Canadian Youth, Sexual Health and HIV/AIDS Study, 2002 Protective Measures at Last Intercourse, Grade 9 (%)

0

10

20

30

40

50

60

70

80

None Pill Other Condom

MaleFemale

Canadian Youth, Sexual Health and HIV/AIDS Study, 2002 Protective Measures at Last Intercourse, Grade 11 (%)

0

10

20

30

40

50

60

70

80

None Pill Other Condom

MaleFemale

Canadian Youth, Sexual Health and HIV/AIDS Study, 2002Condom/Pill Use at Last Intercourse, Grade 9&11 (%)

0

10

20

30

40

50

60

70

80

G9/M G11/M G9/F G11/F

PillCondom

B.C. Adolescent Health Survey 2003 (McCreary Centre Society) Condom Use

at Last Intercourse, Ages 14 & 18

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Condomuse at last

intercourse

Age 14 - 81%

Age 18 - 61%

Canadian Youth, Sexual Health and HIV/AIDS StudyTop Four Reasons Females Give for Not Using Condoms

at last Intercourse, Grade 9 & 11 (%)

0

5

10

15

20

25

30

35

40

Notexpecting

sex

Othermethod

used

Don't likecondoms

Havefaithful

partner

Grade 9Grade 11

Serial Monogamy = Multiple, Sequential, Monogamous (presumed) Relationships

• Behavioural Pattern• 1) New sexual relationship begins (condoms used)• 2) New relationship becomes established/presumed to

be monogamous. STI symptom free partners discontinue condom use in favour of OC’s for contraception, other method, or nothing.

• 3) Relationship ends.• 4) New sexual relationship begins. Condoms used and

then discontinued. (Pattern repeats).• Net Effect on STI Risk

• Unprotected sex with multiple partners.

Reducing Chlamydia by Increasing/Maintaining Condom Use in Ongoing Relationships: An IMB Approach to

Intervention

• Information: Key chlamydia facts with emphasis on prevalence, asymptomatic nature, health consequences. Reality of serial monogamy among 15-24 age group.

• Motivation: Why/how does this info apply to me? E.g., “Am I an unprotected serial monogamist?” “What are the benefits to me if I act on this info?” “What could happen if I don’t?”

• Behavioural Skills: “OK, I need to act, but how?” e.g., condom negotiation. “I’m happy with my decision to start taking the pill but my doctor said we should continue using condoms. That way we are fully protected and do not have to worry about it and can just enjoy ourselves.” If he says “I know I’m clean, I haven’t had sex with anybody else in months” you can say “as far as I know I don’t have an STI either, but either one of us could have an infection without knowing it so I want to use condoms.”

• For More Information on an Information-Motivation-Behavioural Skills (IMB) Approach to Sexual Health Education See:

• The Canadian Guidelines for Sexual Health Education (Public Health Agency of Canada)