Biology · Ch 3 — Reproductive Health
Sexually Transmitted Infections (STIs)
Sexually Transmitted Infections (STIs)
Understanding Sexually Transmitted Infections
Sexually transmitted infections (STIs) are diseases that spread primarily through sexual contact. The textbook uses the older term "Sexually Transmitted Diseases" (STDs), but the modern, more accurate term is STIs — because a person can be infected without showing any disease symptoms. This distinction matters for exams: an infection is the presence of a pathogen; a disease is the visible illness that may or may not follow.
The key point is that STIs are not a single disease — they are a group of infections caused by different types of pathogens (bacteria, viruses, fungi, protozoa, or even parasites like mites). Their only common thread is the mode of transmission: sexual contact (vaginal, anal, or oral). Some can also spread through non-sexual routes like blood transfusion, sharing needles, or from mother to child during pregnancy or childbirth.
Common STIs and Their Causes
The textbook lists several important STIs. You need to know the causative agent for each — this is a frequent exam question.
| Disease | Causative Agent | Type of Pathogen |
|---|---|---|
| Gonorrhoea | Neisseria gonorrhoeae | Bacterium |
| Syphilis | Treponema pallidum | Bacterium |
| Chlamydiasis | Chlamydia trachomatis | Bacterium |
| Trichomoniasis | Trichomonas vaginalis | Protozoan |
| Genital herpes | Herpes simplex virus (HSV) | Virus |
| Hepatitis-B | Hepatitis B virus (HBV) | Virus |
| HIV/AIDS | Human Immunodeficiency Virus (HIV) | Virus |
| Genital warts | Human Papillomavirus (HPV) | Virus |
Among these, Hepatitis-B and HIV are particularly dangerous because they can also spread through blood and from mother to child — not just sexually. This is why blood screening and safe injection practices are critical.
Symptoms and Progression
STIs do not always announce themselves immediately. Many are asymptomatic in the early stages — especially in women. This is a major reason why infections spread unknowingly.
When symptoms do appear, they commonly include:
- Itching, burning sensation during urination or discharge from the genital tract
- Sores, blisters, or warts on the genitals or surrounding skin
- In advanced stages of syphilis: rashes, fever, and eventually damage to the heart, brain, and nerves
A common exam trap: students think all STIs cause visible symptoms. The textbook explicitly states that many are asymptomatic — especially in females. So a person can be infected and infectious without knowing it.
Why STIs Are a Major Public Health Concern
In India, STIs are reported to be especially common among people aged 15–24 — the age group most students reading this fall into — which is exactly why awareness and early detection matter so much at this stage of life.
The consequences go beyond the infection itself:
- Pelvic Inflammatory Disease (PID) in women, which can cause infertility
- Ectopic pregnancy (pregnancy outside the uterus) due to damaged fallopian tubes
- Stillbirth or neonatal death if an infected mother passes the infection to her baby
- Increased risk of HIV transmission — having an STI makes it easier to acquire or transmit HIV
The textbook emphasises that STIs are a major preventable cause of infertility — especially in women. This is a direct link to the chapter's theme of reproductive health.
Prevention — The Only Real Cure
There is no vaccine for most STIs (except Hepatitis-B and HPV). Treatment exists for bacterial and protozoan STIs (antibiotics/antiparasitics), but viral STIs like herpes and HIV can only be managed, not cured. Therefore, prevention is the cornerstone.
The textbook lists these preventive measures:
- Avoid sex with unknown or multiple partners — the single most effective step.
- Use condoms consistently and correctly — they provide a physical barrier against most STIs.
- Maintain personal hygiene — especially genital hygiene.
- Seek early medical help if any symptom appears — do not self-medicate or ignore it.
- Get tested if you suspect exposure — many STIs are curable if caught early.
For exams, remember the phrase: "Avoid, protect, detect, treat." Avoid risky behaviour, protect with condoms, detect early through testing, and treat promptly.