Sexually Transmitted Infections
பாலியல் ரீதியாக பரவும் நோய்த்தொற்றுகள்
Biology does not forgive ignorance. STIs are not just social issues; they are biological failures of the reproductive system that bypass natural barriers. If you think these are rare, you are failing the exam before you even enter the hall.
The idea
Sexually Transmitted Infections (STIs) or Venereal Diseases (VD) are transmitted through sexual intercourse. Pathogens include bacteria like Neisseria gonorrhoeae and Treponema pallidum, and viruses like Herpes simplex and HIV. These infections primarily affect the reproductive tract but can lead to systemic complications. Early detection is mandatory to prevent long-term morbidity.
Why it matters
These are pathogens that have evolved to exploit the mucosal surfaces of the reproductive tract for transmission during sexual contact.
NEET lens
NEET focuses on the causative agents and the classification of STIs. Memorize the list: Gonorrhoea, Syphilis, Genital Herpes, Chlamydiasis, and HIV. Do not confuse bacterial STIs with viral ones, as NTA frequently tests this distinction. Expect at least one question matching the pathogen to the disease.
Clinical significance
Untreated STIs lead to Pelvic Inflammatory Disease (PID), ectopic pregnancies, and infertility. In severe cases, they cause cervical cancer or immune system collapse, as seen in AIDS. The human reproductive ecosystem is fragile; once the mucosal barrier is breached, the risk of secondary infections increases exponentially.
Introduction
Sexually transmitted infections (STIs) are infections transmitted primarily through sexual contact, caused by bacteria, viruses, parasites, or fungi, affecting the reproductive tract and sometimes other systems, preventable by condoms and vaccines (for HPV and hepatitis B).
Core concept
Major STIs: Bacterial (curable with antibiotics): Gonorrhoea: Neisseria gonorrhoeae → urethral/vaginal discharge, pelvic inflammatory disease (PID), infertility. Syphilis: Treponema pallidum → stages (primary chancre → secondary rash → latent → tertiary: cardiovascular/neurological damage). Congenital syphilis if untreated in pregnancy. Chlamydia: Chlamydia trachomatis → often asymptomatic → PID → ectopic pregnancy → infertility. Viral (manageable, not cured): HIV/AIDS: HIV → CD4 T cell destruction → AIDS (immune deficiency). Genital Herpes: HSV-2 → painful blisters, recurrent. HPV: human papillomavirus → genital warts + cervical cancer (high-risk strains 16, 18). Vaccine available (Gardasil, Cervarix). Hepatitis B: sexual + blood-borne → liver cirrhosis/cancer. Vaccine available. Parasitic: Trichomoniasis: Trichomonas vaginalis → vaginal discharge, itching.
Go deeper
HIV mechanism: HIV (retrovirus) → infects CD4+ T helper cells (via CD4 receptor + CCR5/CXCR4 co-receptor) → reverse transcribes RNA → DNA → integrates into host genome → replication → more HIV → CD4 cell death → CD4 count falls → AIDS when CD4 < 200/μL. AIDS: opportunistic infections (PCP pneumonia, toxoplasmosis, CMV retinitis, Kaposi sarcoma). ART (antiretroviral therapy) controls HIV, prevents AIDS.
From Class 10
Some infections spread through sexual contact. These are called sexually transmitted infections (STIs) or sexually transmitted diseases (STDs).