UPSC CSE Prelims
Human Health & Disease Previous Year Questions (PYQs)

Detailed Explanation:

Monoclonal antibodies (mAbs) are laboratory-made proteins designed to recognize and bind to a specific antigen.

• Statement I is Correct: They are man-made proteins produced in laboratories.

• Statement II is Correct: They bind to specific antigens and help the immune system identify or neutralize harmful pathogens.

• Statement III is Correct: Monoclonal antibodies are used in treating and preventing certain viral infections, including the Nipah virus.

• Therefore, all three statements are correct, making Option D the correct answer.

Statement-wise Analysis

Notes: Monoclonal Antibodies (mAbs)

What are Monoclonal Antibodies?

Monoclonal antibodies are identical laboratory-produced antibodies designed to target a specific antigen.

How do they work?

• Bind to a specific antigen.

• Block pathogens from infecting cells.

• Help the immune system destroy infected or abnormal cells.

Major Uses

• Cancer treatment

• Autoimmune diseases

• Viral infections (COVID-19, Ebola, Nipah)

• Diagnostic tests

Important Facts

• Developed using a single clone of immune cells, hence the term "monoclonal."

• They are highly specific compared to conventional drugs.

• Widely used in modern biotechnology and precision medicine.

Detailed Explanation:

Correct Answer: ✅ Option 1 (Nitric Oxide)

Nitric Oxide (NO) is a signaling molecule naturally produced in the human body from the amino acid L-arginine by the enzyme nitric oxide synthase (NOS). It relaxes the smooth muscles of blood vessels, causing vasodilation (widening of blood vessels), which increases blood flow and helps regulate blood pressure.

✅ Nitric Oxide – Correct: Causes vasodilation and improves blood circulation.

❌ Nitrous Oxide (N₂O) – Incorrect: Commonly known as "laughing gas"; used as an anesthetic and analgesic.

❌ Nitrogen Dioxide (NO₂) – Incorrect: A harmful air pollutant that can damage the respiratory system.

❌ Nitrogen Pentoxide (N₂O₅) – Incorrect: A reactive chemical compound with no role in human vasodilation.

Short Notes: Nitric Oxide (NO)

• Discovered as an important biological messenger; awarded the 1998 Nobel Prize in Physiology or Medicine.

• Produced from L-arginine by nitric oxide synthase (NOS).

• Causes vasodilation, increasing blood flow and lowering blood pressure.

• Plays a key role in cardiovascular health.

• Involved in neurotransmission and immune responses.

• Drugs like Nitroglycerin act by releasing nitric oxide.

• Deficiency of NO may contribute to hypertension and vascular diseases.

• Acts as a short-lived gaseous signaling molecule.

Detailed Explanation:

Answer: Option 1 — Controlling the viral diseases spread by mosquitoes

The Wolbachia method is a biological intervention that uses Wolbachia bacteria to control mosquito-borne viral diseases, particularly dengue, Zika, chikungunya, and yellow fever. When Wolbachia is introduced into Aedes aegypti mosquitoes (which don't naturally carry it), it reduces the mosquito's ability to transmit these viruses to humans. Additionally, Wolbachia spreads through mosquito populations via maternal transmission, making it a self-sustaining and environmentally friendly approach to disease control.

📝 Short Notes: Wolbachia Method for Vector Control

• What is Wolbachia: A naturally occurring bacterium found in approximately 60% of insect species, but not in Aedes aegypti or Aedes albopictus mosquitoes.
• Mechanism: When introduced into Aedes mosquitoes, Wolbachia interferes with virus replication, reducing vector competence for dengue, Zika, chikungunya, and yellow fever viruses.
• Self-sustaining: Wolbachia is maternally inherited; infected females pass the bacteria to their offspring, ensuring its persistence in mosquito populations.
• Cytoplasmic Incompatibility: Eggs produced by uninfected females mating with Wolbachia-infected males do not hatch, giving Wolbachia-carrying mosquitoes a reproductive advantage.
• Implementation: Successfully deployed by the World Mosquito Program in countries like Australia, Indonesia, Brazil, Colombia, and India (pilot projects in Pune and Delhi).
• Advantages: Safe for humans and environment, cost-effective in the long term, does not involve genetic modification, and targets multiple diseases simultaneously.

Detailed Explanation:

Answer: Option 4 — They protect the body from the diseases caused by pathogens.

B cells and T cells are both lymphocytes and key components of the adaptive immune system that specifically defend the body against pathogens like viruses, bacteria, fungi, and parasites. B cells produce antibodies that recognize and neutralize specific antigens on pathogens, while T cells either directly kill infected cells (cytotoxic T cells) or help coordinate the immune response (helper T cells).

❌ Option 1 – Incorrect: While immune cells can respond to allergens, the primary role of B and T cells is pathogen defense, not allergen protection.
❌ Option 2 – Incorrect: Pain and inflammation alleviation is not the primary function of B and T cells; they are involved in immune response.
❌ Option 3 – Incorrect: B and T cells are immunoactive, not immunosuppressants; they enhance rather than suppress immune function.
✅ Option 4 – Correct: This accurately describes the primary role of B and T cells in adaptive immunity against pathogenic diseases.

📝 Short Notes: B Cells and T Cells

Detailed Explanation:

Answer: Option 2 — 2 and 3 only

This question tests knowledge about different COVID-19 vaccine platforms used in India. Statement 1 is incorrect because Covishield is a viral vector vaccine (using chimpanzee adenovirus), not an mRNA vaccine. Statements 2 and 3 are correct as they accurately describe the platforms used for Sputnik V and COVAXIN respectively.

❌ Statement 1 – Incorrect: Covishield is a viral vector vaccine using chimpanzee adenovirus (ChAdOx1), not an mRNA platform vaccine.
✅ Statement 2 – Correct: Sputnik V uses a vector-based platform with two different human adenovirus vectors (rAd26 and rAd5) in a two-dose regimen.
✅ Statement 3 – Correct: COVAXIN, developed by Bharat Biotech, is an inactivated pathogen-based vaccine using the whole-virion inactivated Vero cell platform.

📝 Short Notes: COVID-19 Vaccine Platforms

Detailed Explanation:

Answer: Option 3 — Both 1 and 2

Recombinant vector vaccines utilize genetic engineering to insert pathogen genes into harmless carrier organisms (vectors), which then deliver these genes into human cells to produce antigens and trigger immunity. Both viruses (like Adenoviruses in Covishield) and bacteria (like attenuated Salmonella or BCG) can serve as vectors in these vaccines.

✅ Statement 1 – Correct: Genetic engineering is essential for developing recombinant vector vaccines, involving the insertion of pathogen antigen genes into a vector's genetic material.
✅ Statement 2 – Correct: Both bacteria (e.g., Salmonella, BCG) and viruses (e.g., Adenovirus, VSV) are used as vectors to deliver antigens.

📝 Short Notes: Recombinant Vector Vaccines

• Technology: Uses genetic engineering to insert genes encoding pathogen antigens into harmless viral or bacterial vectors
• Mechanism: Vectors deliver genetic material into host cells, which then produce antigens triggering immune response
• Viral Vectors: Adenoviruses (Covishield/Sputnik V), Vesicular Stomatitis Virus (Ebola vaccine - Ervebo), Modified Vaccinia Ankara (MVA)
• Bacterial Vectors: Attenuated Salmonella typhimurium, Mycobacterium bovis (BCG), Listeria monocytogenes strains
• Advantages: Strong cellular and humoral immunity, no live pathogen used, scalable production
• Examples: COVID-19 vaccines (AstraZeneca/Covishield, J&J, Sputnik V), Ebola vaccine (Ervebo), experimental TB and malaria vaccines

Detailed Explanation:

Answer: Option 4 — spread of viral diseases

ACE2 (Angiotensin-Converting Enzyme 2) is a protein receptor found on human cell surfaces that became widely discussed during the COVID-19 pandemic. The SARS-CoV-2 virus uses ACE2 as its primary entry point into human cells, binding to this receptor through its spike protein to infect cells in the lungs, heart, kidneys, and other organs.

📝 Short Notes: ACE2 Receptor

• Full Form: Angiotensin-Converting Enzyme 2
• Normal Function: ACE2 is an enzyme that plays a crucial role in regulating blood pressure and cardiovascular function by converting angiotensin II to angiotensin (1-7)
• Location: Found on cell surfaces in multiple organs including lungs (alveolar cells), heart, kidneys, intestines, and blood vessels
• Role in COVID-19: Acts as the cellular receptor that SARS-CoV-2 spike protein binds to for viral entry into cells
• Research Significance: Target for therapeutic interventions including soluble ACE2, monoclonal antibodies, and small molecule inhibitors to block viral entry
• Previous Connection: The original SARS-CoV virus (2003) also used ACE2 as its receptor, making it a known vulnerability in coronavirus infections

Detailed Explanation:

Answer: Option 2 — 2 Only

Statement 1 is incorrect because adenoviruses have double-stranded DNA genomes, not single-stranded DNA. Retroviruses have single-stranded RNA genomes (not double-stranded DNA), which they reverse-transcribe into DNA using reverse transcriptase. Statement 2 is correct as adenoviruses are a common cause of the common cold, and AIDS is indeed caused by HIV, a retrovirus.

❌ Statement 1 – Incorrect: Adenoviruses have double-stranded DNA genomes; retroviruses have single-stranded RNA genomes, not double-stranded DNA.
✅ Statement 2 – Correct: The common cold can be caused by adenoviruses, and AIDS is caused by HIV, which is a retrovirus.

📝 Short Notes: Viral Genome Types

• DNA Viruses: Generally replicate in the nucleus using host cell machinery (exceptions: poxviruses replicate in cytoplasm)
• RNA Viruses: Most replicate in the cytoplasm; carry their own RNA polymerase
• Retroviruses: Unique in possessing reverse transcriptase enzyme that synthesizes DNA from RNA template
• Common Cold Causes: Rhinoviruses (most common), coronaviruses, adenoviruses, and others
• HIV Classification: Lentivirus genus of the Retroviridae family; targets CD4+ T cells

Detailed Explanation:

Answer: Option 2 — 1 and 2 only

Pneumococcal Conjugate Vaccines (PCVs) are crucial in India's immunization program as they protect against multiple serious diseases caused by Streptococcus pneumoniae and help combat antibiotic resistance. Statement 3 is incorrect as no vaccine is completely free from side effects or allergic reactions.

✅ Statement 1 – Correct: PCVs are highly effective against pneumonia, meningitis (inflammation of brain and spinal cord membranes), and sepsis (blood infection) caused by Streptococcus pneumoniae bacteria.
✅ Statement 2 – Correct: PCVs reduce dependence on antibiotics by preventing pneumococcal infections, thereby addressing the growing problem of antibiotic-resistant bacterial strains.
❌ Statement 3 – Incorrect: Like all vaccines, PCVs can cause mild side effects (redness, swelling, soreness at injection site) and rare allergic reactions; no vaccine is completely side-effect-free.

📝 Short Notes: Pneumococcal Conjugate Vaccines (PCVs)

• Causative Organism: Streptococcus pneumoniae (pneumococcus) — a bacterium with over 90 serotypes.
• Diseases Prevented: Pneumonia, meningitis, sepsis, otitis media (ear infection), and bacteremia.
• Types of Vaccines: PCV10 (protects against 10 serotypes) and PCV13 (protects against 13 serotypes).
• India's Immunization Program: PCV introduced in Universal Immunization Programme (UIP) in 2017; given at 6, 10, and 14 weeks of age.
• Public Health Impact: Reduces child mortality, prevents pneumococcal diseases (leading cause of death in children under 5), and decreases antibiotic use.
• Antibiotic Resistance: PCVs help combat drug-resistant pneumococcal strains by preventing infections, reducing need for antibiotics.
• Common Side Effects: Mild reactions like fever, irritability, injection site reactions; serious allergic reactions are rare but possible.

Detailed Explanation:

Answer: Option 2 — Hepatitis B, unlike Hepatitis C, does not have a vaccine.

This statement is incorrect because a highly effective vaccine for Hepatitis B has been available since 1982, whereas no vaccine exists for Hepatitis C. The question asks for the statement that is NOT correct.

✅ Statement 1 – Correct: Hepatitis B virus is transmitted through similar routes as HIV (blood contact, sexual contact, mother-to-child transmission).
❌ Statement 2 – Incorrect: Hepatitis B has a vaccine; Hepatitis C does not have a vaccine.
✅ Statement 3 – Correct: Globally, Hepatitis B and C infections combined far exceed HIV infections (approximately 325 million vs 38 million).
✅ Statement 4 – Correct: Chronic Hepatitis B and C infections can remain asymptomatic for many years before causing liver damage.

📝 Short Notes: Hepatitis B & C

Detailed Explanation:

Answer: Option 2 — 2 and 3 only

Multi-drug resistance (MDR) in microbial pathogens arises primarily from improper antibiotic use and environmental exposure to antibiotics. Incorrect dosing and incomplete treatment courses allow resistant strains to survive and multiply, while widespread antibiotic use in livestock farming creates selection pressure for resistant bacteria that can spread to humans through the food chain.

❌ Statement 1 – Incorrect: Genetic predisposition affects individual susceptibility to infections but does not cause multi-drug resistance in pathogens; resistance develops in microbes, not humans.

✅ Statement 2 – Correct: Taking incorrect doses, skipping doses, or not completing antibiotic courses allows partially resistant bacteria to survive and develop full resistance through natural selection.

✅ Statement 3 – Correct: Routine use of antibiotics in livestock for growth promotion and disease prevention creates resistant bacteria that can transfer to humans via food, direct contact, or environmental contamination.

❌ Statement 4 – Incorrect: While chronic diseases may increase infection frequency, they do not directly cause antibiotic resistance in microbial pathogens; resistance is a microbial adaptation, not a patient characteristic.

📝 Short Notes: Antimicrobial Resistance (AMR)

• Definition: AMR occurs when microorganisms evolve mechanisms to survive exposure to antimicrobial drugs that would normally kill them or inhibit their growth.
• Main Causes in India: Irrational use of antibiotics (self-medication, incomplete courses), over-the-counter availability without prescription, use in agriculture and aquaculture, poor infection control in healthcare settings.
• Mechanisms of Resistance: Enzymatic degradation of drugs (e.g., beta-lactamases), alteration of drug targets, reduced drug permeability, efflux pumps that expel antibiotics.
• Agricultural Connection: Antibiotics used as growth promoters in livestock create resistant bacteria; these can transfer resistance genes to human pathogens through horizontal gene transfer.
• Public Health Impact: Makes common infections harder to treat, increases healthcare costs, prolongs hospital stays, increases mortality rates.
• Government Initiatives: National Action Plan on AMR (2017), Red Line Campaign for responsible antibiotic use, regulations on antibiotic sales, AMR surveillance networks.
• WHO Priority: Listed as one of top 10 global public health threats; requires coordinated action across human health, animal health, and environmental sectors (One Health approach).

Detailed Explanation:

Answer: Option 3 — Both 1 and 2

✅ Statement 1 – Correct: Zika virus is primarily transmitted by the Aedes aegypti mosquito in tropical regions. This is the same mosquito species that transmits dengue, chikungunya, and yellow fever. The mosquito becomes infected when it bites an infected person and can then transmit the virus to other people through subsequent bites.

✅ Statement 2 – Correct: Sexual transmission of Zika virus is well-documented and possible. The virus can be transmitted through vaginal, anal, and oral sex. It can persist in semen for several months, making sexual transmission a significant route of infection even in areas without active mosquito transmission. Pregnant women are particularly at risk as Zika can cause severe birth defects.

Therefore, both statements are correct.

Detailed Explanation:

The 2014–2016 Ebola outbreak was the most widespread epidemic of Ebola virus disease (EVD) in history, primarily affecting West African countries.

The outbreak began in Guinea in December 2013 and rapidly spread to neighboring Liberia and Sierra Leone, causing over 11,000 deaths and massive socio-economic disruption. These three countries accounted for the vast majority of cases and were frequently mentioned in global news coverage.

Detailed Explanation:

H1N1 virus is a subtype of Influenza A virus that causes Swine flu, which was declared a pandemic by WHO in June 2009.

The virus contains glycoproteins haemagglutinin (H) and neuraminidase (N), hence named H1N1, and was also responsible for the 1918 Spanish Flu outbreak.

Detailed Explanation:

❌ Statement 1 – Incorrect: Diphtheria has not been eradicated; India still administers the Pentavalent vaccine (introduced in 2011–12) which includes DPT (Diphtheria, Pertussis, Tetanus) component, indicating ongoing disease burden.

❌ Statement 2 – Incorrect: Chickenpox (Varicella) remains endemic in India; the Varicella vaccine is available but not part of the Universal Immunization Programme (UIP), and cases occur regularly across the country.

✅ Statement 3 – Correct: Smallpox was declared eradicated from India in 1975 (last case in 1975), and WHO certified global eradication in 1980; India played a key role in the worldwide eradication campaign.