Sexually transmitted infections (STIs)

What are sexually transmitted infections?

In plain words: STIs pass from person to person mainly through sexual contact. Many cause few symptoms at first, so people may not know they are infected; several bacterial and parasitic STIs are curable, while viral infections require different management, and NCERT gives a few simple principles for preventing them.

Common STIs

NCERT names these as some of the common STIs (page 47):

• gonorrhoea;
• syphilis;
• genital herpes;
• chlamydiasis;
• genital warts;
• trichomoniasis;
• hepatitis-B;
• HIV, which can progress to AIDS without effective treatment; it is discussed in Chapter 7 (page 47).

Reading note: the chapter’s opening list of contents calls this section “Sexually Transmitted Diseases” (page 41), and the Summary writes “Sexually Transmitted Diseases (STIs)” (page 49); the section itself is headed Sexually Transmitted Infections (STIs). An STI can exist without symptoms or disease. Also, RTI and STI are not exact synonyms: RTI describes the infection site, whereas STI describes transmission; some reproductive-tract infections are not sexually transmitted (UNFPA, Breaking the Cycle of Transmission).

Spread through needles, blood and from mother to foetus

Some of these infections, like hepatitis-B and HIV, can also be transmitted (page 47):

• by sharing injection needles, surgical instruments, etc., with infected persons;
• by transfusion of blood;
• from an infected mother to the foetus.

Beyond the NCERT text: HIV can also pass from mother to child during childbirth and through breast milk (HIVinfo, NIH, Preventing Perinatal Transmission of HIV).

Cure, symptoms and why detection is late

Except for hepatitis-B, genital herpes and HIV infections, other diseases are completely curable if detected early and treated properly.

NCERT Biology (Class 12), Section 3.4, page 47

• When present, possible symptoms include itching, fluid discharge, slight pain, swellings, etc., in the genital region (page 47).
• People of any sex can be asymptomatic. NCERT emphasises this in females (page 47), but absence of symptoms never proves absence of infection.
• The absence or mildness of symptoms early on, and the social stigma attached to STIs, deter infected people from timely detection and proper treatment (page 47).

NCERT slip (page 47): the quoted list leaves genital warts among the infections that are “completely curable”. Beyond the NCERT text: genital warts are caused by the human papillomavirus (HPV), and MedlinePlus (US National Library of Medicine, public domain) says: “There is no treatment for HPV, but your health care provider can treat genital warts.” Most HPV infections (9 out of 10) go away by themselves within 2 years (CDC, About HPV). Acute hepatitis B usually gets better on its own, while chronic hepatitis B may need antiviral medicines (MedlinePlus, Hepatitis B); genital herpes and HIV can be treated but not cured. The table sums this up. For NCERT-based questions, the incurable STIs are the three NCERT names: hepatitis-B, genital herpes and HIV.

Complications: PID, ectopic pregnancy and infertility

Depending on the pathogen, untreated STIs can lead to complications later (page 47):

• pelvic inflammatory diseases (PID);
• abortions (here, spontaneous loss of the pregnancy, a miscarriage) and still births;
• ectopic pregnancies;
• infertility;
• even cancer of the reproductive tract.

For example, gonorrhoea/chlamydia can cause PID and infertility, while persistent high-risk HPV can cause cervical cancer; wart-causing HPV types are usually different. STIs are a major public-health concern, so prevention, early detection and cure are given prime consideration in reproductive health-care programmes (page 47).

Prevention of STIs

Although everyone is vulnerable, the incidence of STIs is reported to be very high in the 15–24 years age group (page 47). NCERT says there is no reason to panic, because prevention is possible, and gives three simple principles (page 47):

1. avoid sex with unknown partners/multiple partners;
2. always try to use condoms during coitus;
3. in case of doubt, go to a qualified doctor for early detection and get complete treatment if diagnosed with infection.

Beyond the NCERT text: correct use of latex condoms “greatly reduces, but does not eliminate, the risk of catching or spreading HPV”, and an HPV vaccine may help prevent genital warts (MedlinePlus, Genital Warts); the best way to prevent hepatitis B is the hepatitis B vaccine (MedlinePlus, Hepatitis B).

NCERT’s section on barrier contraceptives notes that condoms also protect the user from STIs and AIDS (NCERT Section 3.2, page 44).

Solved examples

Common mistakes to avoid

Quick revision summary

• STIs are transmitted through sexual contact; VD is older terminology, and RTI is an overlapping, distinct category. Examples: gonorrhoea, syphilis, genital herpes, chlamydiasis, genital warts, trichomoniasis, hepatitis-B and HIV (AIDS).
• Hepatitis-B and HIV also spread through shared needles and instruments, blood transfusion and from mother to foetus.
• Several bacterial/parasitic STIs are curable; HIV, HSV, chronic hepatitis B and HPV need separate treatment/clearance distinctions. Infection may be asymptomatic in any sex.
• Complications: PID, abortions, still births, ectopic pregnancy, infertility, cancer of the reproductive tract.
• Incidence is very high at 15–24 years; NCERT’s prevention: avoid unknown/multiple partners, use condoms, see a qualified doctor in case of doubt; HPV/HBV vaccination and testing help too.

Questions students ask

What is the difference between an STI and an STD?

Beyond the NCERT text, an STI is the infection itself and an STD the disease it can turn into: MedlinePlus notes that an STI may cause no symptoms and that “if not treated, an STI can develop into a sexually transmitted disease (STD)”. NCERT does not draw this line and uses both names for one group: it heads its section Sexually Transmitted Infections (STIs) but writes sexually transmitted diseases (STD) on page 42. MeSH, too, files both names under a single heading.

Which STIs are caused by bacteria, which by viruses and which by a protozoan?

Beyond the NCERT text, three of NCERT’s common STIs are bacterial: gonorrhoea (Neisseria gonorrhoeae), syphilis (Treponema pallidum) and chlamydiasis (Chlamydia trachomatis); trichomoniasis is caused by the flagellate protozoan Trichomonas vaginalis; and genital herpes, genital warts, hepatitis-B and HIV are viral (MeSH; MedlinePlus). The cause decides the cure: antibiotics work against the bacterial and parasitic ones, but in MedlinePlus’s words “There is no cure for STIs caused by viruses”, though antivirals help. NCERT’s three not completely curable STIs (page 47) are all viral but omit genital warts, whose virus, HPV, “stays in your body even after treatment” (MedlinePlus).

How can an untreated STI lead to infertility?

Beyond the NCERT text, an untreated STI can lead to infertility through pelvic inflammatory disease (PID), one of the complications NCERT lists (page 47): MeSH describes PID as inflammation of the upper female genital tract, usually from infection climbing up from the cervix, and MedlinePlus names gonorrhoea and chlamydia as its commonest causes. PID scars these organs, the fallopian tubes among them, and the scarring can cause infertility (MedlinePlus); by our reasoning, a scarred, blocked tube can stop the ovum and sperms from meeting in its ampulla.

Is there a vaccine against any STI?

Yes, vaccines exist against hepatitis-B, one of NCERT’s common STIs (page 47): NCERT Chapter 7 gives the hepatitis B vaccine produced from yeast as its example of a vaccine made by recombinant DNA technology (vaccination, page 136). In this approach, antigenic polypeptides of the pathogen are produced in bacteria or yeast, which allows large-scale production and so greater availability for immunisation (NCERT Chapter 7, page 136). Beyond the NCERT text, vaccines also exist against some types of the human papillomavirus (HPV) that cause genital warts (MedlinePlus, Genital Warts).

Practice questions

Try each question first, then open the answer to check your working.

1. Q1. What are the other two names NCERT gives for STIs?

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   NCERT lists VD and RTI (page 47). VD is older terminology; scientifically, RTI and STI overlap but are not identical.

2. Q2. Name two STIs that can also be passed from an infected mother to the foetus.

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   Hepatitis-B and HIV (NCERT page 47).

3. Q3. In which age group does NCERT report a very high incidence of STIs?

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   15–24 years (NCERT page 47).