STIs – Sexually Transmitted Diseases (Edexcel GCSE Biology): Revision Notes
STIs – Sexually Transmitted Diseases
Viruses
Viruses are not considered living organisms because they do not carry out all of the seven life processes, which include:
- Movement
- Respiration
- Sensitivity
- Nutrition
- Excretion
- Reproduction
- Growth
Instead of calling them species, we refer to different "strains" of viruses. These strains consist of a relatively short piece of genetic material (DNA or RNA) surrounded by a protein coat.
Unlike bacterial infections, viral infections cannot be treated with antibiotics because antibiotics are designed to target bacteria, not viruses.
- Infections that spread through sexual contact & intercourse
HIV/AIDS
What is HIV?
- HIV stands for Human Immunodeficiency Virus. It is a virus that weakens the immune system by attacking white blood cells.
How is HIV Contracted?
HIV is transmitted through the exchange of body fluids. This can occur during:
- Unprotected sexual contact.
- Sharing unsterilised needles (e.g., drug use).
- Blood-to-blood contact, such as through cuts or injuries.
- It can also be transmitted from mother to baby during childbirth or breastfeeding.
Symptoms of HIV:
Shortly after infection, people often experience flu-like symptoms, including:
- Fever.
- Sore throat.
- Fatigue.
These symptoms pass quickly, and many people may not know they are infected for years because they don't show other symptoms during this period.
Progression to AIDS:
- AIDS stands for Acquired Immune Deficiency Syndrome.
- Over time (months or years), if HIV is left untreated, the virus destroys more and more white blood cells, weakening the immune system further.
- At this stage, the immune system is so weakened that the body is unable to fight off infections and diseases, leading to AIDS.
Treatment:
There is no cure for HIV/AIDS, but people can be treated with antiviral drugs. These drugs:
- Slow down the replication of the virus.
- Significantly delay the onset of AIDS.
- Help maintain the immune system for a longer period.
| Symptoms | How its spread | How its avoided |
|---|---|---|
| Immune system deteriorates and eventually fails (more vulnerable to pathogens) | Bodily fluids
• Blood
• Semen
• Vaginal fluid | • Condom
• Avoid sharing needles (drug users)
• Medication reduces risk through sex & mother to baby
• Screening
• Treatment |
Chlamydia
What is Chlamydia?
Chlamydia is a bacterial infection caused by the bacterium Chlamydia trachomatis. It is one of the most common sexually transmitted infections (STIs).
How is Chlamydia Contracted?
Chlamydia is mainly spread through:
- Unprotected sexual contact (vaginal, anal, or oral sex) with an infected person.
- It can also be passed from an infected mother to her baby during childbirth.
Symptoms of Chlamydia:
Chlamydia often shows no symptoms, which is why it is sometimes called a "silent" infection.
- Is a kind of bacterium that behaves similarly to a virus and can only reproduce in a host cell
However, when symptoms do appear, they may include:
- Pain or a burning sensation during urination.
- Unusual discharge from the penis or vagina.
- Pain in the lower abdomen (for women).
- Pain during intercourse (for women).
Complications:
If untreated, chlamydia can lead to serious complications, such as:
- Pelvic Inflammatory Disease (PID) in women, which can cause infertility.
- Epididymitis in men, which can cause swelling and pain in the testicles.
Treatment:
Chlamydia can be easily treated with antibiotics.
- It is important to get treated early to prevent long-term health problems.
- Sexual partners should also be treated to prevent re-infection.