Question
Classify sexually transmitted diseases (STDs) based on the causative organism — bacterial, viral, and protozoan. Give symptoms and prevention methods for each.
(NEET + CBSE Class 12)
Solution — Step by Step
| Disease | Pathogen | Key symptoms |
|---|---|---|
| Gonorrhoea | Neisseria gonorrhoeae | Painful urination, pus discharge |
| Syphilis | Treponema pallidum | Painless ulcer (chancre), rash, can affect brain if untreated |
| Chlamydia | Chlamydia trachomatis | Often asymptomatic, urethral discharge, pelvic inflammation |
All bacterial STDs are treatable with antibiotics if detected early.
| Disease | Pathogen | Key symptoms |
|---|---|---|
| HIV/AIDS | Human Immunodeficiency Virus | Destroys helper T-cells, weakened immunity, opportunistic infections |
| Genital herpes | Herpes simplex virus (HSV-2) | Painful blisters on genitals, recurring |
| Genital warts | Human papillomavirus (HPV) | Warts on genitals, some strains cause cervical cancer |
| Hepatitis B | Hepatitis B virus | Liver inflammation, jaundice |
Viral STDs have no complete cure — treatment manages symptoms. Prevention is key.
| Disease | Pathogen | Key symptoms |
|---|---|---|
| Trichomoniasis | Trichomonas vaginalis (protozoan) | Foul-smelling discharge, itching |
Prevention methods for all STDs:
- Use of condoms (most effective barrier method)
- Avoiding multiple partners
- Early detection and treatment
- Blood screening (for HIV, Hepatitis B)
STD Classification Tree by Pathogen Type
flowchart TD
A["STDs — classified by pathogen"] --> B["Bacterial — treatable with antibiotics"]
A --> C["Viral — no complete cure"]
A --> D["Protozoan — treatable"]
B --> B1["Gonorrhoea"]
B --> B2["Syphilis"]
B --> B3["Chlamydia"]
C --> C1["HIV/AIDS"]
C --> C2["Genital herpes"]
C --> C3["Genital warts — HPV"]
C --> C4["Hepatitis B"]
D --> D1["Trichomoniasis"]Why This Works
Classifying STDs by pathogen type immediately tells us about treatment options. Bacterial infections respond to antibiotics. Viral infections cannot be cured but can be managed with antiviral drugs. This classification is the most exam-relevant way to organise STD knowledge.
Early detection is critical because many STDs (especially chlamydia and early HIV) are asymptomatic — the person spreads the infection without knowing they have it.
Common Mistake
Students often list AIDS as a “disease” caused by HIV. Technically, HIV causes infection, and AIDS (Acquired Immunodeficiency Syndrome) is the late stage of HIV infection when the immune system is severely compromised (CD4 T-cell count falls below 200/microlitre). Not everyone with HIV has AIDS. NEET differentiates between HIV infection and AIDS.