CIE iGCSE Biology-16.6 Sexually transmitted infections- Study Notes- New Syllabus
CIE iGCSE Biology-16.6 Sexually transmitted infections- Study Notes – New syllabus
CIE iGCSE Biology-16.6 Sexually transmitted infections- Study Notes -CIE iGCSE Biology – per latest Syllabus.
Key Concepts:
Core
- Describe a sexually transmitted infection (STI) as an infection that is transmitted through sexual contact
- State that human immunodeficiency virus (HIV) is a pathogen that causes an STI
- State that HIV infection may lead to AIDS
- Describe the methods of transmission of HIV
- Explain how the spread of STIs is controlled
What is a Sexually Transmitted Infection (STI)?
✅ Key Definition:
A sexually transmitted infection (STI) is an infection that is passed from one person to another through sexual contact.
🔄 Modes of Transmission:
- Unprotected vaginal, oral, or anal sex
- Direct contact with infected bodily fluids (e.g., semen, vaginal fluids, blood)
- In some cases: from mother to baby during childbirth or breastfeeding
🧷 STI Quick Facts:
STI = infection spread by sexual contact
May be caused by bacteria or viruses
Can affect reproductive health if untreated
🧫 Examples of STIs:
| STI Name | Type of Pathogen | Examples of Effects |
|---|---|---|
| HIV/AIDS | Virus | Weakens the immune system |
| Chlamydia | Bacterium | Can cause infertility if untreated |
| Gonorrhoea | Bacterium | Painful urination, discharge |
| Genital Herpes | Virus | Painful blisters and sores |
| Syphilis | Bacterium | Sores, long-term organ damage |
HIV as a Sexually Transmitted Infection (STI)
✅ Key Statement:
Human Immunodeficiency Virus (HIV) is a pathogen (a virus) that causes a sexually transmitted infection (STI).
📘 What is HIV?
- HIV is a virus that attacks and weakens the immune system, especially white blood cells called T-helper cells.
- It is classified as a sexually transmitted infection because it is commonly spread through unprotected sexual contact.
HIV = virus + STI
Weakens immune system → leads to AIDS
Spread via sex, blood, needles, birth
🔄 Modes of Transmission:
- Unprotected sexual intercourse (vaginal, oral, or anal)
- Sharing needles or syringes
- From mother to baby during pregnancy, childbirth, or breastfeeding
- Through infected blood transfusions
💥 Consequences of HIV:
- If untreated, HIV leads to AIDS (Acquired Immune Deficiency Syndrome), where the immune system becomes too weak to fight off infections and diseases.
- There is no cure, but antiviral drugs can manage the infection and delay progression.
HIV and AIDS
✅ Key Statement:
HIV infection may lead to AIDS.
📘 Explanation:
- HIV (Human Immunodeficiency Virus) is a pathogen that infects and damages the immune system, especially white blood cells (T-helper cells).
- Over time, if HIV is untreated, the immune system becomes severely weakened.
- This condition is called AIDS (Acquired Immune Deficiency Syndrome).
💡 AIDS:
HIV = virus
Untreated HIV → AIDS (immune system fails)
AIDS = final stage of HIV infection
- AIDS is not a virus itself, but a syndrome – a collection of symptoms and infections that occur when the immune system is no longer able to protect the body.
- People with AIDS are highly vulnerable to other infections and diseases, even minor ones that a healthy person could fight off easily.
Methods of Transmission of HIV
✅ Key Statement:
HIV is transmitted through direct contact with certain body fluids from an infected person, most commonly during unprotected sexual activity, but also through other routes.
🔄 Main Modes of Transmission:
| Method | Explanation |
|---|---|
| Unprotected Sexual Intercourse | HIV is present in semen and vaginal fluids. It can enter the body through tiny tears in mucous membranes. |
| Sharing Needles or Syringes | Used needles may carry infected blood, especially among people who inject drugs. |
| Transfusion of Infected Blood | Though rare today (due to blood screening), HIV can be transmitted via infected donor blood. |
| Mother to Baby (Vertical Transmission) | HIV can pass from mother to child during pregnancy, birth, or breastfeeding. |
| Organ Transplantation | If a transplanted organ carries HIV (rare in modern screened transplants), it can infect the recipient. |
❌ HIV is NOT spread by:
- Touching, hugging, or shaking hands
- Sharing food, water, or utensils
- Coughing or sneezing
- Using the same toilet or shower
HIV spreads via:
– Unprotected sex
– Shared needles
– Infected blood
– Mother to baby
NOT spread by touch, air, or casual contact
How the Spread of Sexually Transmitted Infections (STIs) Is Controlled
1. Use of Condoms
- Barrier protection (male or female condoms) prevents the exchange of bodily fluids during sexual contact.
- Effective against most STIs including HIV, gonorrhoea, and chlamydia.
2. Screening and Testing
- Regular STI testing helps detect infections early, especially in sexually active individuals.
- Early diagnosis allows prompt treatment and reduces further transmission.
3. Treatment of Infected Individuals
- Use of antibiotics (for bacterial STIs) or antiviral drugs (for viral STIs like HIV) reduces the risk of spreading infection.
- Treating both partners prevents reinfection.
4. Education and Awareness
- Public health campaigns and school programs promote safe sex practices, reduce stigma, and encourage early testing.
- Knowledge of symptoms and prevention reduces risky behaviour.
5. Contact Tracing
- Identifying and informing recent sexual partners of infected individuals helps stop the spread and ensures those partners also get tested and treated.
6. Avoiding Risky Behaviours
- Limiting the number of sexual partners
- Avoiding sex with people who have visible symptoms
- Not sharing needles or syringes
7. Prevention of Mother-to-Child Transmission
- Pregnant women with STIs like HIV can receive antiretroviral treatment to reduce the chance of passing it to the baby.