Key Points: Sexually Transmitted Diseases
Classification Framework STDs are classified by pathogen type — this determines curability:
- Bacterial STDs → curable with antibiotics
- Viral STDs → not curable (manageable with antivirals)
- Protozoan STDs → curable with antiprotozoal drugs
Bacterial STDs (NTC = curable)
| STD | Pathogen | Type | Key Feature |
|---|---|---|---|
| Gonorrhoea | Neisseria gonorrhoeae | Gram-negative diplococcus | Purulent discharge, painful urination |
| Syphilis | Treponema pallidum | Spirochete | Painless chancre → rash → organ damage |
| Chlamydiasis | Chlamydia trachomatis | Obligate intracellular | Often asymptomatic; causes PID |
Key: Syphilis in primary stage = painless chancre (NOT painful). This "painless" qualifier differentiates it from herpes (painful blisters).
Viral STDs (HHH = NOT curable)
| STD | Pathogen | Unique Feature |
|---|---|---|
| Genital herpes | HSV-2 (herpesvirus) | Painful recurrent blisters |
| Hepatitis B | HBV (DNA virus, Hepadnaviridae) | Liver damage; VACCINE available |
| HIV/AIDS | HIV (retrovirus, ssRNA) | Destroys CD4+ T cells; managed with ART |
Key distinctions:
- HBV = DNA virus; HIV = retrovirus (RNA → DNA via reverse transcriptase). Do not confuse.
- Only Hepatitis B has a preventive vaccine among viral STDs.
- HIV targets CD4+ T helper cells → progressive immune deficiency = AIDS.
Protozoan STD (T = curable)
- Trichomoniasis: Trichomonas vaginalis (flagellated protozoan). Causes frothy yellow-green vaginal discharge, itching, burning. Often asymptomatic in males. Treated with metronidazole.
Prevention Strategies
- Use condoms consistently (covers all STDs)
- Limit number of sexual partners
- Regular screening (especially for asymptomatic chlamydiasis)
- Hepatitis B vaccination (3-dose schedule; part of India's Universal Immunization Programme)
Top NEET Facts on STDs
- Mnemonic NTC (bacteria, curable) + HHH (viruses, not curable) + T (protozoan, curable)
- Chlamydia = obligate intracellular bacterium (cannot survive outside host cells)
- Syphilis = spirochete = painless chancre (primary stage)
- Gonorrhoea = gram-negative diplococcus = purulent discharge
- Hepatitis B = only vaccine-preventable viral STD
- HIV = retrovirus, not curable, managed with ART
- Trichomoniasis = only protozoan STD = curable