NCERT grounding
NCERT Class 12, Chapter 3 (Reproductive Health), Section 3.4 opens with a single definition: infections or diseases transmitted through sexual intercourse are collectively called sexually transmitted infections (STIs), also called venereal diseases (VD) or reproductive tract infections (RTI). The textbook then names exactly eight common STIs — gonorrhoea, syphilis, genital herpes, chlamydiasis, genital warts, trichomoniasis, hepatitis-B and HIV (which leads to AIDS). HIV/AIDS is mentioned here but the detailed mechanism is held back for Chapter 8 (Human Health and Disease); we follow the same split.
“Except for hepatitis-B, genital herpes and HIV infections, other diseases are completely curable if detected early and treated properly.”
NCERT Class 12 · Biology · §3.4
This one sentence is the single most-quoted line of the subtopic in NEET PYQs (asked verbatim in 2023 Q.168 and inverted in 2019 Q.65). Memorise the three exceptions as a set — hepatitis-B, genital herpes, HIV — because every other curability question is built from that contrast.
The eight common STIs
NCERT does not give a tabular list, but the prose names eight infections in a fixed order. Treat that order as a checklist: questions like NEET 2020 Q.28 (“Select the option including all sexually transmitted diseases”) and NEET 2017 Q.85 (matching disease to causative agent) are nothing more than recognition tests against this list.
Three quick patterns emerge. First, every incurable STI is viral (HSV-II, HBV, HIV); every curable STI is bacterial or protozoal. Second, NCERT explicitly defers HIV detail to the chapter on acquired immunity — students should treat HIV/AIDS as a separate chapter topic and only carry forward the curability tag here. Third, although NCERT lists eight, NEET 2017 Q.85 only matched four agents (Neisseria, Treponema, HPV, HIV) — these four are the highest-yield names.
Causative agents at a glance
NEET 2017 Q.85 turned the four most distinctive name pairs into a four-row matching question. Remember the pairs as a compact phonetic block: Gonorrhoea–Neisseria, Syphilis–Treponema, Genital warts–HPV, AIDS–HIV. Once these four are anchored, the protozoan (Trichomonas) and the herpes-II / hepatitis-B viruses fill in by elimination.
Figure 1. Eight common STIs partitioned by curability and paired with their NCERT-named causative agent. Bacterial and protozoal infections (left) are completely curable on early treatment; viral infections (right) form the three-name exception set.
Transmission routes beyond coitus
The defining route is sexual intercourse — that is what places these diseases under one umbrella in the first place. But NCERT explicitly singles out two of the eight, hepatitis-B and HIV, as also transmissible by three additional routes: sharing of injection needles or surgical instruments with infected persons, transfusion of contaminated blood, and from an infected mother to the foetus. NEET 2021 Q.166 tested exactly this — and crucially also tested what does not count: kissing and inheritance are not modes of STI transmission.
Confirmed routes (NCERT)
- Sexual intercourse — applies to all 8 STIs
- Sharing infected injection needles (HBV, HIV)
- Sharing surgical instruments (HBV, HIV)
- Transfusion of contaminated blood (HBV, HIV)
- Infected mother → foetus (vertical, HBV, HIV)
NOT modes of transmission
- Kissing
- Hereditary inheritance (genes)
- Shared utensils / casual social contact
- Mosquito bites (a malaria/filaria distractor)
The trap NEET keeps re-running is to bundle one true route with one false route — “sterile needles” instead of infected needles, or kissing alongside transfusion — and ask which combination is correct. Read the options carefully: a sterile needle is precisely the safeguard, not a route.
Symptoms and complications
NCERT splits the clinical picture into two stages. The early symptoms are deliberately listed as minor and easy to dismiss — itching, fluid discharge, slight pain, and swellings in the genital region. The textbook adds that infected females are often asymptomatic, so they may stay undiagnosed for long stretches. Combined with social stigma, this is what delays treatment.
Delay is what turns a curable bacterial infection into a long-term reproductive injury. NCERT enumerates five named complications of untreated STIs, and these are exactly the matching-stem options NEET uses:
Complications of neglected STIs — memorise as a five-item list. NEET item-banks recycle these five in “select-all-that-apply” formats.
Pelvic Inflammatory Disease (PID)
Ascending infection inflames the uterus, fallopian tubes and ovaries; can scar tubes and end fertility.
Abortions
Spontaneous loss of pregnancy from infected reproductive tract or systemic infection (syphilis, hepatitis-B).
Still births
Foetal death late in gestation, classically linked to untreated maternal syphilis and other vertical infections.
Ectopic pregnancies
Tubal scarring traps the zygote outside the uterus, usually in the fallopian tube — surgical emergency.
Infertility
Chronic tubal blockage or testicular damage. STIs are a leading preventable cause of infertility worldwide.
Cancer of reproductive tract
HPV → cervical cancer; HBV → hepatocellular carcinoma. NCERT phrasing: “or even cancer of the reproductive tract.”
NCERT closes the paragraph with one categorical statement: “STIs are a major threat to a healthy society.” That is the line that justifies the entire RCH programme’s STI screening arm, and it is the line NEET 2023 Q.168 implicitly references when it asks which STI is curable.
Prevention — the NCERT triad
NCERT does not write generic public-health prose. It lists exactly three numbered principles for STI prevention — these are the only three the examination treats as canonical. Treat the wording as fixed; NEET has paraphrased them but never expanded them.
NCERT §3.4 — three prevention principles
-
(i)
Avoid risk-partner sex
Avoid sex with unknown partners or with multiple partners — reduces probability of contacting an infected partner.
-
(ii)
Use condoms
Always try to use condoms during coitus. Mechanical barrier interrupts transmission for all 8 STIs.
-
(iii)
Early detection & complete treatment
In case of doubt, consult a qualified doctor for early diagnosis and complete treatment — curable STIs revert only if treated fully.
Two implicit corollaries follow. First, condoms appear in this chapter twice — once as a barrier contraceptive (Section 3.3) and again here as the only NCERT-named STI barrier. The dual role is exactly why NEET keeps recycling condom-related stems. Second, “complete treatment” is load-bearing: incomplete antibiotic courses for gonorrhoea, syphilis or chlamydia drive resistance and recurrence — so curability is conditional on compliance.
Worked examples
Q. A student lists the following as STIs: gonorrhoea, syphilis, malaria, AIDS, filaria, genital herpes. Which two should be struck off?
A. Strike off malaria and filaria. Malaria is vector-borne (mosquito → Plasmodium) and filaria is also mosquito-transmitted (Wuchereria). NCERT §3.4 lists eight STIs and neither appears. This is the exact distractor pattern in NEET 2020 Q.28, where option (2) “AIDS, Malaria, Filaria” is wrong because of the same two intruders.
Q. Match: (A) Gonorrhoea, (B) Syphilis, (C) Genital warts, (D) AIDS with (i) HIV, (ii) Neisseria, (iii) Treponema, (iv) HPV.
A. A–(ii), B–(iii), C–(iv), D–(i). Memorise as the “N-T-H-H” pneumonic: Neisseria–Treponema–HPV–HIV in the order Gonorrhoea–Syphilis–Warts–AIDS. This is verbatim NEET 2017 Q.85, answer (2).
Q. Among the eight common STIs, which are NOT completely curable even if detected early?
A. Three only — hepatitis-B, genital herpes and HIV (AIDS). All three are viral. The five curable ones — gonorrhoea, syphilis, chlamydiasis, trichomoniasis, genital warts — respond to early, complete antimicrobial therapy. (Note: genital warts are caused by HPV, a virus, but NCERT classifies them as curable along with the rest — the three exceptions are specifically the ones NCERT names.)
Q. Of the following, which can spread venereal diseases? (a) Using sterile needles (b) Transfusion of blood from an infected person (c) Infected mother to foetus (d) Kissing (e) Inheritance
A. Only (b) and (c). Sterile needles are safe — note the wording. Kissing and inheritance are explicitly excluded by NCERT. This is NEET 2021 Q.166 answer (4).
Common confusion & NEET traps
Figure 2. The clinical arc of an untreated STI: minor early symptoms (top left), frequent asymptomatic presentation in females (below), and the six NCERT-listed complications that follow neglect (top right). Early detection at the first node prevents the entire downstream chain.