Epidemiology of STIs

Question 1

What are the symptoms of primary HIV infections?

Answer 1

Sore throat

Fever

Rash

Pharyngitis

Question 2

What is the rate of HIV in the men who have sex with men community in Melbourne?

Answer 2

1 in 10

Question 2

What is disassortative mixing?

Answer 2

The mixing between high risk groups and low risk groups (core with non-core)

eg Married men who have sex with men

Question 2

In which group of people does circumcision reduce transmission of HIV?

Answer 2

In those performing insertative anal sex

Question 3

Is pharyngeal gonorrhoea usually symptomatic or asymptomatic?

Answer 3

Asymptomatic

Question 3

What determines ß (the probability of transmission per partnership)?

Answer 3

Condon use

Types of sex and duration

Cofactors eg coinfections, bleeding HIV

Question 4

What is the definition of basic reproductive rate?

Answer 4

The number of seconday cases of an infection that arise from a primary case at t=0

Question 5

What is PreP?

Answer 5

Pre-exposure prophylaxis for HIV

Question 6

What is concurrency of partners?

Answer 6

When one or more partners in a relationship have other sexual partners while continuing sexual activity with the original partner

Question 7

What occurs at the steady state of an epidemic?

Answer 7

New cases=cured cases

Question 8

What are some strategies for reducing the probability of transmission of HIV?

Answer 8

Reduce cofactors

Reduce viral load

Increase condom use

Change type of sex

Question 10

What an epidemic to occur, what must the basic reproductive rate be?

Answer 10

>1

Question 11

Which is worst for transmission; assortative (high risk with high risk) or disassortative (low risk with high risk)

Answer 11

Assortative

Question 12

When PreP indicated?

Answer 12

When a long term partner is HIV+

Question 13

What is the average duration of infection of people infected with gonorrhoea in urban areas?

Answer 13

A few days

Question 14

By what margin does post exposure prophylaxis reduce the transmission of HIV?

Answer 14

70-80%

Question 15

Which are easier to control, bacterial or viral STIs?

Answer 15

Bacterial

Question 17

Why is the rate of syphilis diagnosis increasing in the recent past?

Answer 17

Less condom usage

More unsafe sex

More partners

Question 18

What is the difference between basic and effective reproductive rate?

Answer 18

In the effective reproductive rate R0 is multiplied by the proportion susceptible

Question 19

How does circumcision reduce the transmission of HIV?

Answer 19

The skin on the glands becomes tougher in the absence of a foreskin > more immune to HIV

Question 21

What is the equation for basic reproductive rate?

Answer 21

R0=BcD

Beta = Transmission probability per sexual partnership

c = Rate of partner change

D = Duration of infection

Question 22

What is the core group in STI transmission?

Answer 22

A small group of people that have many partners and are the core transmitter of the infection

Question 23

What must all interventions to reduce STIs do?

Answer 23

Target the core group to reduce the standard deviation