Sexually Transmitted InfectionsCambridge IGCSE Biology: Revision notes

Section 1

What Is a Sexually Transmitted Infection?

A sexually transmitted infection (STI) is an infection that is transmitted through sexual contact. STIs are one reason why understanding reproduction and sexual health — including the hormonal changes of puberty controlled by testosterone and oestrogen — is an important part of biology.

Key termssexually transmitted infection (STI)

Section 2

What Is HIV and How Is It Linked to AIDS?

Human immunodeficiency virus (HIV) is a pathogen (a virus) that causes an STI. HIV infection may progress to AIDS (acquired immune deficiency syndrome), a condition in which the immune system is severely weakened and can no longer fight off infections effectively.

Key termsHIVAIDS

Common mistake

HIV and AIDS are not the same thing — HIV is the virus (the pathogen); AIDS is the disease/condition that can develop after HIV infection.

Section 3

How Is HIV Transmitted, and How Can Its Spread Be Controlled?

HIV is transmitted through body fluids, including:

Unprotected sexual contact
Contact with infected blood (e.g. sharing needles)
From mother to child during pregnancy, birth, or breastfeeding

The spread of STIs such as HIV can be controlled by:

Using condoms during sexual intercourse
Reducing the number of sexual partners
Screening and testing (including of blood used for transfusions)
Using clean, single-use needles
Health education about risks and prevention

Key termstransmission

Exam tip

When asked to 'explain how the spread of STIs is controlled', give specific named methods (condoms, screening, education) rather than a vague answer like 'be careful'.

Must Know

An STI is an infection transmitted through sexual contact
HIV is a virus that causes an STI and can progress to AIDS
AIDS severely weakens the immune system, making the body vulnerable to other infections
HIV is transmitted via body fluids: sexual contact, infected blood, mother-to-child
Spread of STIs is controlled by condom use, reducing partners, screening/testing, clean needles, and education

That's the notes covered.

Carry on to the next subtopic.