16.6 Sexually transmitted infections
- Syllabus
- 0610–2026–2027
- Topic
- 16.6
- Level
- —
Learning objectives
16.6.1Sexually transmitted infection (STI)• Describe a sexually transmitted infection (STI) as an infection that is transmitted through sexual contact16.6.2Human immunodeficiency virus (HIV) is• State that human immunodeficiency virus (HIV) is a pathogen that causes an STI16.6.3HIV infection may lead to AIDS• State that HIV infection may lead to AIDS16.6.4Methods of transmission of HIV• Describe the methods of transmission of HIV16.6.5Spread of STIs is controlled• Explain how the spread of STIs is controlled
Define a sexually transmitted infection
A sexually transmitted infection (STI) is an infection transmitted through sexual contact.
The infectious agent may pass in sexual fluids or through close contact with infected tissues during sexual activity.
An STI describes a route of transmission, not one specific pathogen type: different STIs can be caused by viruses, bacteria or other pathogens.
Identify HIV as an STI pathogen
Human immunodeficiency virus (HIV) is a virus and a pathogen that causes a sexually transmitted infection.
HIV is the pathogen; AIDS is a condition that may develop after untreated HIV infection. HIV is not a bacterium and is not killed by antibiotics.
Explain how HIV may lead to AIDS
Untreated HIV infects and destroys lymphocytes. As lymphocyte numbers fall, fewer effective immune responses and antibodies can be produced, so the person becomes vulnerable to opportunistic infections and some cancers. This advanced loss of immune function is AIDS.
HIV infection → lymphocyte destruction → weakened immune response → opportunistic disease → AIDS.
HIV infection and AIDS are not identical: a person can have HIV without having developed AIDS, especially when treatment controls the virus.
Describe HIV transmission
| Transmission route | Example |
|---|---|
| sexual fluids | unprotected sexual contact with an infected person |
| infected blood | sharing contaminated needles or receiving unscreened infected blood |
| mother to child | across the placenta, during birth or through breast milk |
HIV is not spread by ordinary social contact, coughing, sneezing or saliva alone. Transmission requires infected body fluids to enter another person's body.
Control the spread of STIs
| Control measure | How it reduces spread |
|---|---|
| abstain from sexual contact or reduce exposure | removes or reduces opportunities for transmission |
| use condoms or femidoms correctly | creates a barrier to infected sexual fluids |
| testing, screening and partner notification | identifies infections and allows contacts to be tested and treated |
| education | explains transmission, prevention and when to seek testing |
| screened blood and sterile, unshared needles | prevents blood-to-blood transmission |
| appropriate treatment | reduces infection or infectiousness; antiretroviral treatment controls HIV |
Contraceptive pills prevent pregnancy but do not form a barrier against STIs. Antibiotics may treat susceptible bacterial STIs, but they do not treat HIV or other viral infections.