Lecture 29 - Epidemiology of STIs

Question 1

What are the local clinical syndromes due to STIs?

Answer 1

• Genital lesions (ulcers, warts)
• Urethritis, vaginitis, cervicitis
• Proctitis (rectal infection)
• Pharyngitis (throat infection)
• Pelvic inflammatory disease (PID)

Question 2

What are the systemic clinical syndromes due to STIs?

Answer 2

HIV–AIDS
• Primary HIV infection
• Immunodeficiency & complications (“opportunistic” infections & malignancies)

Syphilis
• Primary (genital ulcer “chancre”)
• 2o (skin), 3o (brain, spinal cord, blood vessels) • Congenital syphilis infection

Question 3

What are the ways we can diagnose STIs?

Answer 3

• swabs
• microscopy
• culture
• antigen detection assay
• PCR

Question 4

What is an ideal treatment for an STI?

Answer 4

• on the spot
• single dose
• no side effects
• cheap
• effective prevents
• efficient partner treatment

Question 5

What is the reality of treatment that we have to face?

Answer 5

• asymptomatic infection
• multiple infections
• long course treatment needed
• antibiotic resistance
• latency, reactivation
• partners unknown
• no prevention

Question 6

How do we measure the spread of infection?

Answer 6

Reprouctive rate - Ro

Average number of secondary cases produced by one primary case

Question 7

What happens when Ro > 1?

Answer 7

Epidemic

• spread of the disease to many people

Question 8

What happens when Ro = 1?

Answer 8

Endemic

Question 9

What happens when Ro < 1?

Answer 9

Disease eventually disappears

Question 10

What are the determinants of Ro?

Answer 10

Ro = B x c x d

B: transmissability

c: n° of contacts
d: duration of infectivity

Largely dependent on rate of different sexual partners

Question 11

Why do we want to reduce transmission of disease?

Answer 11

Less people potentially infected

Question 12

How do we reduce transmissability?

Answer 12

• condoms

* reduction of other STIs

Question 13

How do we reduce duration of infectivity?

Answer 13

• treatment

Question 14

How can we reduce the n° of contacts?

Answer 14

• core group interventions

* community-wide behavioural change

Question 15

What are the different groups in society?

Answer 15

• general population
• bridging population
• core transmitters

Question 16

How do we manage STIs in Australia?

Answer 16

•  Public awareness 
•  Health services:
- GPs
- Rural
- Sexual health cilics
•  Partner tracing and treatment 
•  Screening 
•  Vaccination (i.e. HPV)
•  Surveillance
•  Promotion of safe sex

Question 17

Why is screening important for management of STIs?

Answer 17

People need to know that they are infected so that they don’t spread it to others

Question 18

Describe promotion of safe sex

Answer 18

• education in schools

* facilitation

Question 19

Describe surveillance of STIs

Answer 19

• Diagnosis:
- State health departments etc.
• Antimicrobial resistance

Question 20

Describe the difficulties faced in the Indigenous populations

Answer 20

• Higher rates of STIs

• chlamydia
• gonorrhoea
• syphilis
• Donovanosis (Klebsiella)

• Treatment obstacles

• limited care access
• difficult partner tracing

Question 21

Compare Gonorrhoea in Indigenous populations and in Melbourne

Answer 21

Rural populations: gonorrhoea is penicillin sensitive

Melbourne: resistance: beta-lactamase producers

Question 22

Describe the trends in chlamydia infection

Answer 22

10% increase per year in Victoria

Question 23

Which age groups are most at risk of Chlamyia infection?

Answer 23

Males: 20-29
Females: 15-19

Question 24

Describe the Chlamydia iceberg

Answer 24

Tip of the iceberg:
• 2500 cases that we see

Underwater:
• tests
• thousands of cases that are being missed

Question 25

What are the control strategies of Chlamydia?

Answer 25

• Surveillance
• Targeted screening of high risk groups
• Education
• Increased community awareness
• Partner notification processes

Question 26

Describe Partner notification processes

Answer 26

• ‘Let them know’
• Trackers
- don’t necessarily know who the person is
• Direct discussion with partner

Question 27

Describe the trends in Gonococcal infections

Answer 27

late 1980s: noted rise in ‘men who have sex with men’

• after HIV treatment, there was a complacency, and a subsequent increase in rates

Question 28

Which groups are most affected by Gonorrhoea?

Answer 28

Males 20-24 yo

Question 29

Describe the trends in Syphilis

Answer 29

2000-2007: increase in incidence

2007-2011: declining due to campaigns

Question 30

Describe the trends in HIV

Answer 30

Late 80’s: rapidly increase
80’s -2000: decreased
2000’s stabilised

Question 31

Which communities are affected by HIV?

Answer 31

Africa: heterosexual population
Australia: men who have sex with men

Question 32

What are the HIV control strategies in Australia??

Answer 32

• testing
• surveillance
• treatment
• Health promotion
- across many different groups