Identify HIV as a viral pathogen that can cause an STI
HIV is human immunodeficiency virus: a viral pathogen that can cause an STI. The host, virus, infection and AIDS disease stage are distinct categories.
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
What kind of pathogen is HIV?
What you will learn
- Distinguish the virus from the infection and host
- Connect a named pathogen with its effects on defence
Original teaching model. Cards show stated mechanisms and conditions.
| Feature | Meaning |
|---|---|
| HIV | Human immunodeficiency virus |
| Type | Viral pathogen |
| Host | Person living with the infection |
| AIDS | Advanced HIV disease stage |
Distinguish the virus from the infection and host
HIV stands for human immunodeficiency virus. It is a virus and a pathogen: a disease-causing agent. HIV can cause an infection transmitted through sexual contact, so it is the required pathogen example in this STI section. It is not a bacterium, an antibiotic or a type of white blood cell. A person living with HIV is the host, not the pathogen.
The infection can affect the immune system, making defence less effective if it progresses without effective treatment. The virus uses living host cells to reproduce; it is not created merely because a person has symptoms or a particular appearance. Naming a pathogen and naming the body system it affects provide different parts of a biological explanation.
Connect a named pathogen with its effects on defence
HIV infection and AIDS are not interchangeable names. HIV names the virus; HIV infection names its presence and activity in the body; AIDS describes an advanced stage of disease involving severe immune damage. The next lessons explain why progression is possible but not automatic for every person, especially with effective care.
The original labelled model represents categories, not a microscope photograph or a measured viral particle count. A schematic virus label cannot diagnose infection, reveal a person’s viral load or establish a transmission route by itself. The written practice checks whether the pathogen, host, infection and possible disease stage have been kept distinct.
Sources for this lesson
Pause and explain
Which category names the host?
Worked example
Classify HIV, a person living with HIV and AIDS.
Show the worked solution
- Name the virus as pathogen and person as host.
- Name AIDS as an advanced disease stage.
Answer HIV is the viral pathogen; the person is the host; AIDS is an advanced stage of HIV disease, not another virus.
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.
Expand HIV and state its pathogen type.
Give me a hint
Use all three words and the virus category.
Compare my reasoning
- Expand human immunodeficiency virus.
- Identify it as a viral pathogen.
HIV means human immunodeficiency virus; it is a viral pathogen that can cause an STI.
Look for these in your work
- Expand correctly
- Give virus and pathogen
Explain why “HIV is a bacterium produced by a visibly sick person” is inaccurate.
Give me a hint
Repair type and appearance-based inference.
Compare my reasoning
- Identify a virus reproducing in host cells.
- Separate symptoms from proof of infection.
HIV is a virus, not a bacterium; it reproduces using living host cells. Appearance alone does not establish HIV infection.
Look for these in your work
- Correct pathogen type
- Reject diagnosis from appearance
A drawing labels the person as pathogen and HIV as a white blood cell. Repair both labels.
Give me a hint
Separate host from infectious agent.
Compare my reasoning
- Identify person as host.
- Identify HIV as virus rather than a defence cell.
The person is the host; HIV is the viral pathogen, not a white blood cell.
Look for these in your work
- Repair both labels
- Keep host and pathogen distinct
Common mistakes
- A person is not the pathogen.
- HIV is a virus, not a bacterium.
What can you explain now?
Which category names the host?
Compare with the explanation
The person living with HIV
The host is distinct from the virus.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain distinguish the virus from the infection and host and connect a named pathogen with its effects on defence. 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.