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Q10:
What are the various routes by which transmission of human immuno-deficiency virus takes place?
Solution :
1. Biological Basis of HIV Transmission
Human Immunodeficiency Virus (HIV) is a lentivirus (a subgroup of retroviruses) that specifically targets the host's immune system, primarily the $CD4^+$ T-lymphocytes. Transmission of the virus is strictly contingent upon the transfer of bodily fluids containing free viral particles or infected immune cells. The virus cannot survive or replicate outside a living host; therefore, transmission requires direct contact with infected fluids via specific biological routes.
2. Primary Routes of HIV Transmission
The transmission of HIV is categorized into four distinct mechanical and biological pathways:
- Sexual Contact: The most prevalent route globally. Transmission occurs through unprotected sexual intercourse (vaginal, anal, or oral) with an infected partner. The presence of mucosal tears or co-existing Sexually Transmitted Infections (STIs) significantly increases the risk of viral entry into the bloodstream.
- Parenteral Exposure (Blood-to-Blood Contact): This involves the direct introduction of infected blood into the circulatory system. This is common among individuals who share contaminated needles, syringes, or other drug-injecting equipment. It also historically included the transfusion of unscreened blood or blood products, though stringent modern screening protocols have mitigated this risk.
- Vertical Transmission (Mother-to-Child): HIV can be transmitted from an infected mother to her child during three specific stages:
- Intrauterine: Through the placenta during pregnancy.
- Intrapartum: During labor and delivery due to exposure to maternal blood and secretions.
- Postpartum: Through breastfeeding, as the virus is present in human breast milk.
- Contaminated Instruments: The use of non-sterile instruments for surgical procedures, dental work, tattooing, or body piercing that have been in contact with infected blood can act as a vector for transmission.
3. Visual Representation of Transmission Dynamics
4. Epidemiological Clarification: What is NOT a Route
It is clinically imperative to note that HIV is not transmitted through casual contact. The following activities do not transmit the virus:
| Non-Transmission Vector | Biological Justification |
|---|---|
| Physical Contact | The virus cannot penetrate intact, healthy skin. |
| Insects (Mosquitoes) | HIV does not replicate within the insect vector; it is digested as food. |
| Sharing Utensils/Water | The virus is inactivated by environmental factors (pH, temperature, drying). |
Final Solution: The transmission of HIV occurs primarily through sexual contact with an infected individual, direct parenteral contact with infected blood (e.g., shared needles/syringes, contaminated blood products), vertical transmission from mother to child (during gestation, parturition, or breastfeeding), and exposure to contaminated surgical or piercing instruments.
More Questions from Class 12 Biology Human Health and Disease EXERCISES
- Q1: What are the various public health measures, which you would suggest as safeguard against infectious diseases?
- Q1: What are the various public health measures, which you would suggest as safeguard against infectious diseases?
- Q2: In which way has the study of biology helped us to control infectious diseases?
- Q2: In which way has the study of biology helped us to control infectious diseases?
- Q3(a): How does the transmission of each of the following diseases take place? (a) Amoebiasis
- Q3(a): How does the transmission of each of the following diseases take place? (a) Amoebiasis
- Q3(b): How does the transmission of each of the following diseases take place? (b) Malaria
- Q3(b): How does the transmission of each of the following diseases take place? (b) Malaria
- Q3(c): How does the transmission of each of the following diseases take place? (c) Ascariasis
- Q3(c): How does the transmission of each of the following diseases take place? (c) Ascariasis
- Q3(d): How does the transmission of each of the following diseases take place? (d) Pneumonia
- Q3(d): How does the transmission of each of the following diseases take place? (d) Pneumonia
- Q4: What measure would you take to prevent water-borne diseases?
- Q4: What measure would you take to prevent water-borne diseases?
- Q5: Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
- Q5: Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
- Q6: Name the primary and secondary lymphoid organs.
- Q6: Name the primary and secondary lymphoid organs.
- Q7(a): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (a) MALT
- Q7(a): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (a) MALT
- Q7(b): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (b) CMI
- Q7(b): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (b) CMI
- Q7(c): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (c) AIDS
- Q7(c): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (c) AIDS
- Q7(d): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (d) NACO
- Q7(d): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (d) NACO
- Q7(e): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (e) HIV
- Q7(e): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (e) HIV
- Q8(a): Differentiate the following and give examples of each: (a) Innate and acquired immunity
- Q8(a): Differentiate the following and give examples of each: (a) Innate and acquired immunity
- Q8(b): Differentiate the following and give examples of each: (b) Active and passive immunity
- Q8(b): Differentiate the following and give examples of each: (b) Active and passive immunity
- Q9: Draw a well-labelled diagram of an antibody molecule.
- Q9: Draw a well-labelled diagram of an antibody molecule.
- Q10: What are the various routes by which transmission of human immuno-deficiency virus takes place?
- Q11: What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?
- Q11: What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?
- Q12: How is a cancerous cell different from a normal cell?
- Q12: How is a cancerous cell different from a normal cell?
- Q13: Explain what is meant by metastasis.
- Q13: Explain what is meant by metastasis.
- Q14: List the harmful effects caused by alcohol/drug abuse.
- Q14: List the harmful effects caused by alcohol/drug abuse.
- Q15: Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?
- Q15: Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?
- Q16: Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.
- Q16: Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.
- Q17: In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
- Q17: In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
CBSE Solutions for Class 12 Biology Human Health and Disease
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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