Connect each STI control measure with the route it interrupts
Match the measure to the route: sexual barriers, screened blood, sterile non-shared equipment, testing and appropriate care. Conditions matter, and no single slogan proves all routes are absent.
Section B15.5 · Sexually transmitted infections
Exam scope and assessment notes
Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.
Before you begin
- Recall pathogens, transmission routes, immune defence, viruses, blood and the difference between prevention and treatment.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which explanation correctly links control to route?
What you will learn
- Explain controls using mechanisms rather than slogans
- Retain the conditions and scope of each measure
Original teaching model. Cards show stated mechanisms and conditions.
| Feature | Meaning |
|---|---|
| Sexual route | Correct consistent condoms; avoid exposure |
| Blood route | Screened supply; sterile non-shared equipment |
| Status and care | Testing; appropriate treatment and partner care |
| Evidence limit | Actual conditions, not appearance or labels |
Explain controls using mechanisms rather than slogans
A useful spread-control explanation names the pathogen, possible route and the part of that route a measure interrupts. Avoiding sexual contact removes that sexual exposure, but it does not by itself remove shared-injection or perinatal routes. Correct and consistent condom use reduces many sexual-transmission risks by providing a barrier; screening donated blood and using sterile non-shared injection equipment address different routes.
A mutually monogamous relationship with a partner who does not have the relevant infection can avoid introducing that infection through outside sexual contacts, provided those conditions actually hold. A relationship label or a healthy appearance does not establish infection status or prove that no other exposure occurred. Testing, appropriate care and accurate information help people understand status and control spread without using stereotypes.
Retain the conditions and scope of each measure
Testing can identify infection and connect people with appropriate treatment and partner care. Treatment effects depend on the pathogen: suitable treatment can cure some bacterial infections, whereas effective HIV treatment controls the virus. For HIV, maintaining an undetectable viral load on effective antiretroviral treatment prevents sexual transmission. This specific evidence should not be replaced by a vague claim that any medicine instantly prevents every STI.
The route-control cards compare measures side by side rather than show a causal sequence between them. Several measures may work together, and each has defined conditions. An exam answer should explain how a chosen control affects a relevant route, acknowledge what it does not establish and avoid inferring any real person’s status from an invented classroom record.
Sources for this lesson
Pause and explain
What makes a mutually monogamous uninfected-partner statement conditional?
Worked example
Why does sterile non-shared injection equipment address a different route from condoms?
Show the worked solution
- Identify retained contaminated blood and injection entry.
- Contrast a sexual-contact barrier.
Answer Sterile non-shared equipment interrupts blood transfer through injection equipment; condoms provide a barrier during relevant sexual contact.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Explain how three controls address sexual contact, donated blood and injection equipment.
Give me a hint
Match each measure with its source and entry pathway.
Compare my reasoning
- Use correct consistent condoms for sexual contact.
- Use screened blood and sterile non-shared equipment for blood-related routes.
Condoms reduce sexual exposure through a barrier; blood screening helps prevent contaminated donation; sterile non-shared equipment interrupts transfer of retained blood.
Look for these in your work
- Name three controls
- Explain their different routes
A fictional campaign says avoiding sexual contact removes every HIV route. Evaluate the claim.
Give me a hint
Other supported routes remain distinct.
Compare my reasoning
- Identify the sexual route removed.
- Identify shared blood equipment or perinatal routes not addressed.
Avoiding sexual contact removes that exposure, but does not by itself remove blood-equipment or perinatal routes; the every-route claim is unsupported.
Look for these in your work
- Credit the specific effect
- Retain other routes
A fictional couple is described as monogamous and healthy-looking. Does the record establish both people are uninfected?
Give me a hint
Separate relationship and appearance evidence from infection evidence.
Compare my reasoning
- Reject appearance as status proof.
- Keep actual status and outside exposures as conditions.
No. The description does not establish infection status or all exposure conditions; a monogamous label and appearance are not sufficient evidence.
Look for these in your work
- Reject status inference
- State the missing conditions
Common mistakes
- One route-specific measure does not remove all HIV routes.
- Appearance and relationship labels do not establish infection status.
What can you explain now?
What makes a mutually monogamous uninfected-partner statement conditional?
Compare with the explanation
Actual infection status and absence of other exposures matter
The label alone does not establish these conditions.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain explain controls using mechanisms rather than slogans and retain the conditions and scope of each measure. Use the stated route, conditions and evidence before opening the solutions.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.