Who this is for: Cambridge IGCSE Biology (0610) students who want STI knowledge — HIV/AIDS, gonorrhoea, transmission and prevention — to become reliable marks instead of vague health advice with no syllabus detail.
What query it owns: how to understand and revise sexually transmitted infections in Cambridge IGCSE Biology.
Why this is safe: this page owns the STI revision-guide angle, while Tutopiya’s Sexually Transmitted Infections subtopic page owns the learning resource and the free STI quiz owns the practice.

Sexually transmitted infections (STIs) are diseases spread mainly through sexual contact. Cambridge IGCSE Biology (0610) focuses on HIV/AIDS and gonorrhoea — their causes, effects on the body, and methods of prevention. This guide covers the syllabus definitions, the comparison tables examiners expect, and the question types that appear every year.

Key takeaways

• HIV (Human Immunodeficiency Virus) attacks lymphocytes, weakening the immune system; AIDS is the late stage when the immune system is severely damaged.
• Gonorrhoea is caused by a bacterium; symptoms include pain on urination and discharge; treatable with antibiotics.
• HIV is a virus — antibiotics do not work against it; antiretroviral drugs slow progression.
• Prevention: condoms, limiting sexual partners, early testing and treatment.
• HIV can be transmitted through blood, sexual fluids and from mother to fetus across the placenta.

What are sexually transmitted infections in Cambridge IGCSE Biology?

STIs are infections passed from one person to another primarily through sexual contact. HIV destroys white blood cells (lymphocytes), leaving the body unable to fight infections and some cancers — this advanced stage is AIDS. Gonorrhoea is a bacterial STI that infects the reproductive tract; if untreated it can cause infertility. Both can be reduced by barrier methods (condoms) and responsible sexual behaviour.

You can read the full explanation and notes on Tutopiya’s Sexually Transmitted Infections subtopic page before you attempt questions.

The core ideas you must master

Idea	What it means	How the exam uses it
HIV	Virus attacking lymphocytes	”Describe the effect of HIV on the body.”
AIDS	Severe immune deficiency stage	”Distinguish HIV and AIDS.”
Gonorrhoea	Bacterial STI	”State the cause of gonorrhoea.”
Antibiotics	Kill bacteria	”Suggest treatment for gonorrhoea.”
Condoms	Barrier prevention	”Describe methods to prevent STIs.”

HIV/AIDS vs gonorrhoea

Feature	HIV/AIDS	Gonorrhoea
Pathogen type	Virus	Bacterium
Main effect	Destroys lymphocytes; weakens immune system	Infects reproductive tract; discharge, pain urinating
Treatment	Antiretroviral drugs (no cure)	Antibiotics
Prevention	Condoms, limit partners, no sharing needles	Condoms, limit partners, early treatment
Can cross placenta	Yes	Can affect newborn during birth

STI prevention methods

Method	How it works	STI relevance
Condoms	Physical barrier	Reduces transmission of HIV and gonorrhoea
Limiting partners	Reduces exposure risk	Lowers chance of contact with infected person
Early testing/treatment	Identifies and treats infection	Prevents spread of gonorrhoea
Avoid sharing needles	Prevents blood transmission	Reduces HIV spread

STIs in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical STI stem
Describe	What happens / method	”Describe the effect of HIV on the immune system.”
State	Short factual answer	”State the pathogen that causes gonorrhoea.”
Explain	Cause and effect	”Explain why antibiotics do not treat HIV.”
Suggest	Apply prevention	”Suggest two ways to reduce the spread of STIs.”
Distinguish	Clear difference	”Distinguish HIV and AIDS.”

Worked exam-style stems (how to answer the wording)

1. “Describe the effect of HIV on the body.” HIV destroys lymphocytes (white blood cells), weakening the immune system so the body cannot fight infections and cancers effectively. Mark-scheme reward: lymphocytes + immune system weakened.
2. “Explain why antibiotics are effective against gonorrhoea but not HIV.” Gonorrhoea is caused by bacteria, which antibiotics kill; HIV is a virus, and antibiotics only work against bacteria. Reward: pathogen type linked to treatment.
3. “Suggest two methods to reduce the spread of sexually transmitted infections.” Use condoms during sexual intercourse; limit the number of sexual partners; seek early testing and treatment. Reward: syllabus prevention methods.

When you can recognise the wording instantly, work the full set on Tutopiya’s Sexually Transmitted Infections quiz and link to Immunity for lymphocyte context.

How STIs connect to the rest of the syllabus

STIs link to Sexual Reproduction in Humans (placenta transmission), Immunity (lymphocytes) and Medicinal Drugs (antibiotics). The Cambridge IGCSE Biology resource hub links every Reproduction subtopic.

Common mistakes students make

• Using antibiotics to treat HIV (HIV is a virus).
• Saying HIV and AIDS are the same thing (HIV is the virus; AIDS is the late disease stage).
• Describing HIV as attacking red blood cells (it attacks lymphocytes).
• Omitting condoms as a specific prevention method in suggest questions.
• Confusing gonorrhoea ( bacterial ) with HIV ( viral ).

When you need more support

If STI questions keep costing marks — especially HIV effect describe stems — work through the Sexually Transmitted Infections quiz, then get focused help from a Cambridge IGCSE Biology tutor.

Frequently asked questions

Are STIs hard in Cambridge IGCSE Biology? Only two STIs are required — HIV/AIDS and gonorrhoea — but marks are lost confusing pathogen types and treatments.

What is the difference between HIV and AIDS? HIV is the virus that infects the body; AIDS is the condition when the immune system is severely damaged by HIV.

Can HIV be cured with antibiotics? No — HIV is a virus. Antibiotics only kill bacteria, so they work against gonorrhoea but not HIV.

How do I revise STIs effectively? Learn the HIV/AIDS vs gonorrhoea compare table, practise prevention suggest questions, then take the STI quiz.

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