Q80. Which pairing of a disease with its causative category is incorrect?
[UPSC CDS (I) 2026]
(A) Polio — viral
(B) Athlete’s foot — fungal
(C) Dengue — non-viral
(D) Whooping cough — bacterial
Answer: (C) Dengue — non-viral
Explanation: Dengue is caused by dengue virus, a flavivirus transmitted mainly by Aedes mosquitoes. Polio is also viral, athlete’s foot is a fungal infection, and whooping cough results from Bordetella pertussis bacteria. Thus the dengue classification is the erroneous pair.
Q79. Which laboratory method allows one-tube detection of dengue, chikungunya and Zika viruses?
[RRB Group D, 14 August 2026]
(A) Bacterial culture
(B) Multiplex real-time RT-PCR
(C) Blood glucose estimation
(D) Gram staining
Answer: (B) Multiplex real-time RT-PCR
Explanation: Multiplex real-time reverse-transcription PCR identifies genetic material from several RNA viruses in a single reaction. It offers rapid differential diagnosis where dengue, chikungunya and Zika share fever-like presentations. Gram staining and bacterial culture cannot directly identify these viral genomes.
Q78. How many assertions are correct:
Viruses cannot persist in sea water;
Cannot infect bacteria; and
Cannot alter host transcription?
[UPSC CSE Prelims 2025]
(A) Exactly one
(B) Exactly two
(C) All three
(D) None
Answer: (D) None
Explanation: All three assertions are false. Numerous viruses occur in marine environments; bacteriophages infect bacteria; and viruses can redirect gene expression in infected host cells. Viruses rely on living systems for replication, but they are ecologically widespread and biologically active.
Q77. Identify the incorrectly described vector–disease–pathogen combination.
[RPSC RAS Prelims 2025]
(A) Aedes – chikungunya – bacteria
(B) Culex – filariasis – parasitic worm
(C) Anopheles – malaria – protozoan
(D) Aedes – dengue – virus
Answer: (A) Aedes – chikungunya – bacteria
Explanation: Chikungunya is caused by an alphavirus rather than a bacterium, although Aedes mosquitoes are important vectors. Filariasis involves parasitic nematodes, malaria involves Plasmodium protozoa, and dengue is viral. The key is distinguishing a vector from the actual pathogen.
Q76. QDENGA, a tetravalent vaccine, is intended to prevent which mosquito-borne disease?
[RRB NTPC (UG), 4 September 2025]
(A) Dengue
(B) Malaria
(C) Chikungunya
(D) Japanese encephalitis
Answer: (A) Dengue
Explanation: QDENGA (TAK-003) targets dengue, which has four major virus serotypes. A tetravalent formulation aims to generate protection across these types. Malaria is protozoan, whereas chikungunya and Japanese encephalitis are caused by different viruses requiring different prevention strategies.
Q75. India observes National Vaccination Day on 16 March in connection with which vaccine campaign?
[RRB Group D, 16 December 2025]
(A) Influenza
(B) Polio
(C) Yellow fever
(D) Rabies
Answer: (B) Polio
Explanation: India marks 16 March as National Vaccination Day to commemorate the first oral polio vaccine administration under the 1995 campaign. The programme highlights childhood immunisation and efforts to interrupt poliovirus transmission before it can produce irreversible paralysis.
Q74. The National Polio Surveillance Network in India was developed with support from which organisation?
[RRB Group D, 19 December 2025]
(A) UNEP
(B) World Bank
(C) World Health Organization
(D) UNDP
Answer: (C) World Health Organization
Explanation: The World Health Organization collaborated with India on the National Polio Surveillance Network. Surveillance for acute flaccid paralysis and virological testing is essential because poliovirus can circulate silently even when relatively few infected people develop paralytic disease.
Q73. Which vaccine developed by Jonas Salk uses inactivated poliovirus?
[SSC CGL Tier-I, 9 September 2024]
(A) Salk vaccine
(B) Imvanex
(C) HDCV rabies vaccine
(D) TAB vaccine
Answer: (A) Salk vaccine
Explanation: Jonas Salk developed the inactivated poliovirus vaccine, administered by injection. It differs from the oral, live-attenuated vaccine associated with Albert Sabin. Both strategies have been central to controlling poliomyelitis, but their formulations and routes of administration differ.
Q72. Which virus most commonly causes the ordinary common cold?
[SSC MTS, 4 November 2024]
(A) Hepatitis A virus
(B) Influenza A virus
(C) Rhinovirus
(D) Rabies virus
Answer: (C) Rhinovirus
Explanation: Rhinoviruses account for many common colds, typically causing sneezing, nasal discharge and a sore throat. Other respiratory viruses can produce similar symptoms. Hepatitis A affects the liver, while rabies primarily attacks the nervous system after exposure to infected saliva.
Q71. COVID-19 is commonly discussed as a disease of which origin category?
[SSC MTS, 15 October 2024]
(A) Dietary deficiency
(B) Waterborne parasitosis
(C) Zoonotic origin
(D) Inherited metabolic disorder
Answer: (C) Zoonotic origin
Explanation: COVID-19 is caused by SARS-CoV-2, a coronavirus with a likely animal evolutionary origin. Zoonosis refers to disease transmission involving animal reservoirs and people. Once established in humans, COVID-19 spreads mainly between people through infectious respiratory particles.
Q70. Which vaccine entered an Indian Phase-III clinical trial announced by ICMR and Panacea Biotec in August 2024?
[RRB Technician Grade-I, 20 December 2024]
(A) Dengue vaccine
(B) Typhoid conjugate vaccine
(C) Malaria vaccine
(D) Hepatitis E vaccine
Answer: (A) Dengue vaccine
Explanation: The announcement concerned a tetravalent dengue vaccine trial. Dengue has four major viral serotypes, making balanced immune protection particularly important. Clinical trials assess vaccine safety and effectiveness; starting Phase III does not itself imply a vaccine is licensed for general use.
Q69. For what public-health purpose is the Wolbachia method applied?
[UPSC CSE Prelims 2023]
(A) Reducing mosquito transmission of viral illnesses
(B) Converting straw to packaging
(C) Manufacturing bioplastics
(D) Making biochar
Answer: (A) Reducing mosquito transmission of viral illnesses
Explanation: Wolbachia is a bacterium introduced or maintained in mosquito populations to reduce their ability to transmit dengue and some other arboviruses. The method addresses the vector rather than treating infected patients and is investigated as a sustainable disease-control approach.
Q68. Which pathogen–disease assignment is correct for peptic ulcer, dengue, elephantiasis and malaria?
[UPPSC PCS Prelims 2023]
(A) Bacteria, protozoan, worm, virus
(B) Virus, bacteria, worm, protozoan
(C) Bacteria, virus, worm, protozoan
(D) Worm, virus, bacteria, protozoan
Answer: (C) Bacteria, virus, worm, protozoan
Explanation: Peptic ulcers are often associated with Helicobacter pylori bacteria; dengue is viral; elephantiasis commonly results from filarial nematodes; and malaria comes from Plasmodium protozoa. The question tests pathogen groups rather than simply the names of diseases.
Q67. Which pair of hepatitis viruses is principally associated with transmission through infected blood?
[WBCS Mains (Science) 2023]
(A) Hepatitis A and E
(B) Hepatitis A and B
(C) Hepatitis B and C
(D) Hepatitis D and E only
Answer: (C) Hepatitis B and C
Explanation: Hepatitis B and C can spread through contaminated blood, including unsafe injections or shared needles. Hepatitis B can also spread sexually and during childbirth. Hepatitis A and E predominantly follow faecal–oral pathways, frequently linked to contaminated food or water.
Q66. Which illness among these is caused by a virus?
[SSC CHSL 2022 cycle, 21 March 2023]
(A) Chickenpox
(B) Tuberculosis
(C) Whooping cough
(D) Malaria
Answer: (A) Chickenpox
Explanation: Chickenpox is caused by varicella-zoster virus and commonly gives an itchy vesicular rash. Tuberculosis and whooping cough are bacterial infections, while malaria is protozoan. Correctly identifying the pathogen helps distinguish vaccine approaches and appropriate antimicrobial treatment.
Q65. Which mosquito genus transmits the virus responsible for chikungunya?
[SSC CHSL 2022 cycle, 10 March 2023]
(A) Culex
(B) Mansonia
(C) Aedes
(D) Anopheles
Answer: (C) Aedes
Explanation: Chikungunya virus is an alphavirus spread mainly by Aedes aegypti and Aedes albopictus mosquitoes. It often causes fever accompanied by pronounced joint pain. Aedes mosquitoes can also carry dengue and Zika viruses, whereas Anopheles is best known for malaria transmission.
Q64. Which statements about COVID-19 vaccines are correct:
Covishield is mRNA;
Sputnik V uses a viral vector;
Covaxin uses inactivated virus?
[UPSC CSE Prelims 2022]
(A) First and second
(B) Second and third
(C) First and third
(D) All three
Answer: (B) Second and third
Explanation: Covishield uses a non-replicating adenoviral vector, not an mRNA platform. Sputnik V also uses adenoviral vectors, whereas Covaxin is an inactivated whole-virus vaccine. Different platforms expose the immune system to viral antigens without causing ordinary COVID-19 disease.
Q63. What kind of pathogen produces dengue fever?
[RRB NTPC CBT-2, 14 June 2022]
(A) Virus
(B) Fungus
(C) Bacterium
(D) Nematode
Answer: (A) Virus
Explanation: Dengue results from infection with dengue virus, typically transmitted by infected female Aedes mosquitoes. Four major dengue serotypes are recognised. Prevention focuses substantially on avoiding bites and controlling breeding sites, since the mosquito carries the virus between human hosts.
Q62. Which mosquito group is the principal carrier of dengue virus?
[UPPSC PCS Prelims 2022]
(A) Anopheles
(B) Aedes
(C) Culex
(D) Mansonia
Answer: (B) Aedes
Explanation: Female Aedes mosquitoes, especially Aedes aegypti, spread dengue through bites. These mosquitoes often breed in domestic water containers and tend to bite during daytime. Dengue is distinct from malaria, which is carried predominantly by female Anopheles mosquitoes.
Q61. In the 2022 polio drive, oral vaccine drops were administered to children below which age?
[RRB Group D, 20 September 2022]
(A) Five years
(B) Ten years
(C) Three years
(D) Two years
Answer: (A) Five years
Explanation: Pulse Polio rounds traditionally target children younger than five years to protect against poliovirus infection. Vaccinating this age group helps reduce the risk of paralysis and interrupt transmission. The strategy supplements routine immunisation and continued surveillance.
Q60. Which assertion about viruses is generally incorrect?
[CGPSC 2021 Prelims, held 13 February 2022]
(A) A virus may possess DNA or RNA
(B) RNA viruses can mutate comparatively quickly
(C) Most DNA viruses necessarily contain single-stranded DNA
(D) Viruses lack independent cellular metabolism
Answer: (C) Most DNA viruses necessarily contain single-stranded DNA
Explanation: Many DNA viruses carry double-stranded DNA, so claiming they are usually single-stranded is misleading. Viral genomes may be DNA or RNA, single- or double-stranded. Mutation rates vary considerably; many RNA viruses evolve rapidly because of replication characteristics.
Q59. What was the volume of a single Covishield vaccine dose in the examined vaccination schedule?
[CGPSC 2021 Prelims, held 13 February 2022]
(A) 1.0 mL
(B) 2.0 mL
(C) 0.5 mL
(D) 1.5 mL
Answer: (C) 0.5 mL
Explanation: The standard Covishield dose used in the programme was 0.5 mL by intramuscular injection. Covishield employs an adenovirus-vector platform to express the SARS-CoV-2 spike antigen. Dose schedules and recommendations should follow the contemporary national programme or product label.
Q58. Which disease in the following group is bacterial rather than viral?
[UPSC NDA (I) 2022]
(A) AIDS
(B) Dengue
(C) COVID-19
(D) Typhoid
Answer: (D) Typhoid
Explanation: Typhoid is caused by Salmonella Typhi, a bacterium transmitted commonly through contaminated food or water. AIDS, dengue and COVID-19 are caused by HIV, dengue virus and SARS-CoV-2 respectively. The difference matters because antibiotics target bacteria, not viruses directly.
Q57. Which groups can normally grow on a cell-free artificial medium: bacteria, fungi and viruses?
[UPSC CSE Prelims 2021]
(A) Bacteria and fungi only
(B) Fungi and viruses only
(C) Bacteria and viruses only
(D) All three
Answer: (A) Bacteria and fungi only
Explanation: Many bacteria and fungi grow on suitable artificial culture media because they possess their own cellular metabolism. Viruses must infect susceptible living cells to replicate. Laboratory virology commonly uses cell cultures, embryonated eggs or other living systems rather than nutrient agar alone.
Q56. Assess the claims:
Adenoviruses have single-stranded DNA whereas retroviruses have double-stranded DNA;
Adenoviruses can cause colds whereas HIV is a retrovirus.
[UPSC CSE Prelims 2021]
(A) First only
(B) Second only
(C) Both
(D) Neither
Answer: (B) Second only
Explanation: The first statement reverses the usual genome types: adenoviruses possess double-stranded DNA, while HIV is an RNA retrovirus. The second is correct. Some adenoviruses cause respiratory illness, and retroviruses copy their RNA into DNA using reverse transcriptase.
Q55. ACE2 attracted attention in relation to which subject?
[UPSC CSE Prelims 2021]
(A) GM crop markers
(B) Satellite navigation
(C) Wildlife tracking
(D) Entry and spread of certain coronaviruses
Answer: (D) Entry and spread of certain coronaviruses
Explanation: Angiotensin-converting enzyme 2 is a receptor used by SARS-CoV-2 to enter many susceptible cells. The viral spike protein attaches to it as part of the entry process. ACE2 also performs normal physiological functions independently of infection.
Q54. What is the official name of the virus that causes COVID-19?
[WBCS Prelims 2021]
(A) SARS-CoV-2
(B) COVID-19 virus
(C) nCOVID-19
(D) Coronavirus disease 2019
Answer: (A) SARS-CoV-2
Explanation: SARS-CoV-2 is the name of the virus, while COVID-19 is the disease it causes. The distinction matters: virus naming follows taxonomic conventions, whereas diseases receive separate public-health names. SARS-CoV-2 is related to the coronavirus associated with SARS.
Q53. Which disease among cholera, AIDS, cold and dengue is not viral?
[RRB NTPC CBT-I, 14 March 2021]
(A) Cholera
(B) AIDS
(C) Common cold
(D) Dengue
Answer: (A) Cholera
Explanation: Cholera is caused by the bacterium Vibrio cholerae and commonly spreads through contaminated water. AIDS results from HIV, colds from several respiratory viruses and dengue from dengue virus. Pathogen classification is the central distinction in this question.
Q52. Japanese encephalitis virus most directly damages which organ?
[RPSC RAS Prelims 2021]
(A) Skin
(B) Red blood cells
(C) Brain
(D) Lungs
Answer: (C) Brain
Explanation: Japanese encephalitis is inflammation of the brain associated with Japanese encephalitis virus. It is transmitted mainly through Culex mosquitoes, with pigs and water birds important in the transmission cycle. Severe illness may involve seizures, altered consciousness and neurological injury.
Q51. Which virus causes the historically widespread disease smallpox?
[UPSC NDA (II) 2021]
(A) Adenovirus
(B) Variola virus
(C) Coxsackievirus
(D) Aichi virus
Answer: (B) Variola virus
Explanation: Smallpox was caused by variola virus, an orthopoxvirus. Worldwide vaccination campaigns stopped naturally occurring transmission, allowing WHO to declare eradication in 1980. It should not be confused with chickenpox, which is caused by varicella-zoster virus.
Q50. Which illness is not caused by a virus?
[SSC CHSL 2020 cycle, 11 August 2021]
(A) Leprosy
(B) Measles
(C) Smallpox
(D) Rabies
Answer: (A) Leprosy
Explanation: Leprosy is caused by Mycobacterium leprae, a bacterium affecting skin and peripheral nerves. Measles, smallpox and rabies arise from distinct viruses. Their prevention and treatment differ, highlighting why memorising the organism behind each disease remains important.
Q49. Which combination lists only diseases caused by coronaviruses?
[MPPSC Prelims 2020]
(A) SARS, MERS and COVID-19
(B) Malaria, dengue and influenza
(C) Typhoid, polio and rabies
(D) Hepatitis B, mumps and measles
Answer: (A) SARS, MERS and COVID-19
Explanation: SARS, MERS and COVID-19 are caused by different coronaviruses. Severe acute respiratory syndrome and Middle East respiratory syndrome involve related but distinct agents from SARS-CoV-2. The coronavirus family also includes pathogens causing some milder respiratory infections.
Q48. Why do usual antibacterial antibiotics not work directly against viruses?
[UPSC NDA (I) 2020]
(A) All viruses manufacture chlorophyll
(B) Viruses possess bacterial cell walls
(C) Viruses lack the bacterial metabolic targets of antibiotics
(D) Antibiotics always destroy antibodies
Answer: (C) Viruses lack the bacterial metabolic targets of antibiotics
Explanation: Antibiotics act on structures or pathways such as bacterial ribosomes, cell walls or enzymes. Viruses do not possess those bacterial targets and replicate using host cells. A bacterial complication of viral illness may still require antibiotic treatment when clinically indicated.
Q47. Which statement about hepatitis B and C is false?
[UPSC CSE Prelims 2019]
(A) Hepatitis B can spread through routes similar to HIV
(B) Hepatitis B has no vaccine whereas hepatitis C does
(C) Chronic infection may be asymptomatic for years
(D) Both viruses can cause long-term liver illness
Answer: (B) Hepatitis B has no vaccine whereas hepatitis C does
Explanation: An effective hepatitis B vaccine exists, while no hepatitis C vaccine is currently licensed. Both viruses can establish long-term infections and cause cirrhosis or liver cancer. Screening is important because symptoms may be absent during years of infection.
Q46. Which claim about viruses is wrong?
[UPSC NDA (II) 2019]
(A) They require living cells for replication
(B) They are obligate intracellular parasites
(C) They can photosynthesise to make food
(D) Outside a host they may be metabolically inactive
Answer: (C) They can photosynthesise to make food
Explanation: Viruses have no chloroplasts, independent energy metabolism or photosynthetic machinery. They reproduce only inside living host cells using host resources. Their extracellular particles can remain infectious without carrying out ordinary cellular processes such as growth or photosynthesis.
Q45. Rotavirus vaccination primarily prevents a severe form of which condition in children?
[SSC MTS, 7 August 2019]
(A) Diarrhoea
(B) Poliomyelitis
(C) Hepatitis B
(D) AIDS
Answer: (A) Diarrhoea
Explanation: Rotavirus is a major cause of gastroenteritis and severe dehydration in infants and young children. Rotavirus vaccines reduce severe diarrhoeal illness and hospitalisation. They do not prevent polio, viral hepatitis or HIV, which involve different pathogens.
Q44. Which plant condition is not generally caused by a virus?
[RPSC Senior Teacher Science 2019]
(A) Little-leaf disease of brinjal
(B) Yellow-vein mosaic of bhindi
(C) Banana bunchy top
(D) Papaya leaf curl
Answer: (A) Little-leaf disease of brinjal
Explanation: Little-leaf disease of brinjal is associated with phytoplasma, a wall-less bacterial pathogen. The other listed plant diseases are associated with viruses. This is an important distinction because plant infections may involve viruses, fungi, bacteria, phytoplasmas or viroids.
Q43. What best explains the relatively rapid genetic evolution of many RNA viruses?
[UPSC CDS (II) 2018]
(A) RNA genomes can be relatively error-prone during replication
(B) Viruses divide by binary fission
(C) Viruses photosynthesise
(D) Their genomes never undergo mutation
Answer: (A) RNA genomes can be relatively error-prone during replication
Explanation: Many RNA viruses replicate using polymerases with limited proofreading, allowing mutations to accumulate relatively quickly. Mutation rates differ among virus families; coronaviruses have some proofreading capability. Genetic variation may influence transmission, immunity, diagnostics and antiviral resistance.
Q42. Which genetic material is carried in HIV virions?
[UPSC NDA (I) 2018]
(A) Single-stranded circular DNA
(B) Double-stranded DNA
(C) Single-stranded RNA
(D) Double-stranded RNA
Answer: (C) Single-stranded RNA
Explanation: HIV is a retrovirus carrying two copies of single-stranded RNA. During infection it uses reverse transcriptase to generate a DNA copy that integrates into the host genome. This replication strategy distinguishes retroviruses from ordinary DNA viruses.
Q41. Who inaugurated the 2018 Pulse Polio campaign?
[RRB Group D, 19 September 2018]
(A) President Ram Nath Kovind
(B) Prime Minister Jawaharlal Nehru
(C) Vice-President B. D. Jatti
(D) President Rajendra Prasad
Answer: (A) President Ram Nath Kovind
Explanation: President Ram Nath Kovind launched the 2018 Pulse Polio campaign. The programme delivered oral polio vaccine to young children while maintaining vigilance against importation of poliovirus. Vaccination coverage remains important even after national elimination of endemic transmission.
Q40. Regarding Zika, which assertions are correct: Aedes mosquitoes can transmit it, and sexual transmission can occur?
[UPSC CSE Prelims 2017]
(A) First only
(B) Second only
(C) Both
(D) Neither
Answer: (C) Both
Explanation: Zika virus can be carried by Aedes mosquitoes, which also transmit dengue. It can additionally spread through sexual contact and from mother to fetus. Infection during pregnancy is significant because of its association with congenital abnormalities, including microcephaly.
Q39. What does the term bacteriophage denote?
[MPPSC Prelims 2017]
(A) A bacterium with a tail
(B) A new bacterial colony
(C) A bacterium that infects a virus
(D) A virus that infects bacteria
Answer: (D) A virus that infects bacteria
Explanation: Bacteriophages, or phages, are viruses that attach to and replicate inside bacteria. They demonstrate that bacteria themselves can be viral hosts. Phages occur widely in soil, water and the human microbiome, and they are studied for biotechnology and antibacterial applications.
Q38. What kind of microorganism produces both poliomyelitis and chickenpox?
[SSC CGL, 9 August 2017]
(A) Bacteria
(B) Protozoa
(C) Algae
(D) Viruses
Answer: (D) Viruses
Explanation: Poliomyelitis is caused by poliovirus, and chickenpox by varicella-zoster virus. Although they differ in clinical effects and transmission, both require host cells for reproduction. Bacteria, protozoa and algae do not cause these particular illnesses.
Q37. In dengue illness, the count of which blood component may decrease markedly?
[UPSC NDA (I) 2017]
(A) Monocytes
(B) Platelets
(C) Eosinophils
(D) Neutrophils
Answer: (B) Platelets
Explanation: Dengue can cause thrombocytopenia, meaning a reduced platelet count. Platelets help maintain haemostasis, but clinical severity depends on more than the count alone. Warning signs, circulation and plasma leakage require careful medical assessment in suspected severe dengue.
Q36. The Breteau index helps monitor the mosquito vector most closely linked with which illness?
[UPPSC Staff Nurse 2017]
(A) Cholera
(B) Dengue
(C) Typhoid
(D) Leprosy
Answer: (B) Dengue
Explanation: The Breteau index measures the number of water-holding containers positive for Aedes larvae or pupae per hundred houses inspected. It is an entomological surveillance measure used in dengue control programmes, rather than a diagnostic test for infected patients.
Q35. Which organisms can be infected by viruses: bacteria, fungi, or plants?
[UPSC CSE Prelims 2016]
(A) Bacteria and fungi only
(B) Plants only
(C) Bacteria and plants only
(D) All three
Answer: (D) All three
Explanation: Bacteriophages infect bacteria, mycoviruses infect fungi, and plant viruses infect many crops. Viral host range extends far beyond humans. Their replication depends on specific host cells, explaining why an organism can be susceptible to some viruses but not others.
Q34. HIV weakens immunity mainly by damaging which cell class?
[UPSC CDS (II) 2016]
(A) Mast cells
(B) Platelets
(C) Red blood cells
(D) Lymphocytes
Answer: (D) Lymphocytes
Explanation: HIV principally targets CD4-positive T-helper lymphocytes. Progressive loss and dysfunction of these immune cells reduce coordinated immune responses, allowing opportunistic infections. Platelets and red blood cells may be affected indirectly, but they are not the primary defining cellular targets.
Q33. The switch from trivalent to bivalent oral vaccine was made for which disease?
[RPSC RAS Prelims 2016]
(A) Diphtheria
(B) Malaria
(C) Typhoid
(D) Polio
Answer: (D) Polio
Explanation: The global switch from trivalent to bivalent oral poliovirus vaccine removed the type-2 Sabin component from routine OPV in 2016. Bivalent OPV targeted poliovirus types 1 and 3, with inactivated vaccine support. This was part of polio endgame planning.
Q32. In standard examination terminology, H1N1 influenza was popularly called what?
[UPSC CSE Prelims 2015]
(A) AIDS
(B) Bird flu
(C) Dengue
(D) Swine flu
Answer: (D) Swine flu
Explanation: The 2009 pandemic strain of influenza A(H1N1) became popularly known as swine flu. This name reflected its genetic ancestry, although sustained transmission occurred between humans. Influenza viruses have segmented RNA genomes that can evolve through mutation and reassortment.
Q31. Among diphtheria, chickenpox and smallpox, which had been eradicated in India?
[UPSC CSE Prelims 2014]
(A) Diphtheria and chickenpox
(B) Smallpox alone
(C) All three
(D) None
Answer: (B) Smallpox alone
Explanation: Smallpox is the viral disease eradicated globally through vaccination, certified by WHO in 1980. Chickenpox still occurs, and diphtheria remains a bacterial vaccine-preventable disease. Eradication means permanent worldwide reduction of natural incidence to zero.
Q30. Among chikungunya, hepatitis B and HIV, which may spread through contaminated tattoo needles?
[UPSC CSE Prelims 2013]
(A) Chikungunya only
(B) Hepatitis B and HIV
(C) Chikungunya and HIV
(D) All three
Answer: (B) Hepatitis B and HIV
Explanation: Nonsterile tattooing equipment may expose people to blood-borne viruses such as hepatitis B and HIV. Chikungunya normally spreads by infected mosquito bites. Sterilisation, single-use needles and infection-control precautions reduce the risk of blood-borne transmission.
Q29. Which statement about viruses is correct?
[UPSC CSE Prelims 2013]
(A) They lack independent energy-generating machinery
(B) They grow in ordinary nutrient broth
(C) They spread exclusively through insects
(D) They always contain both DNA and RNA genomes
Answer: (A) They lack independent energy-generating machinery
Explanation: Viruses cannot independently generate cellular energy. Replication requires living cells, so ordinary synthetic nutrient medium alone is insufficient. Viral transmission occurs through multiple routes such as air, contact, food, water and vectors; different viruses possess either DNA or RNA genomes.
Q28. Which disease is not normally transmitted by Asian tiger mosquitoes?
[UPPSC PCS Prelims 2013]
(A) Yellow fever
(B) Dengue
(C) Chikungunya
(D) Japanese encephalitis
Answer: (D) Japanese encephalitis
Explanation: Japanese encephalitis is predominantly transmitted through Culex mosquitoes. Asian tiger mosquitoes, Aedes albopictus, can transmit dengue and chikungunya and may be involved in other arboviral transmission under some conditions. Matching a virus with the dominant vector prevents confusion.
Q27. HIV, which causes AIDS, belongs to which virus category?
[UPPSC Lower Subordinate Prelims 2013]
(A) Adenovirus
(B) Tobacco mosaic virus
(C) T-even bacteriophage
(D) Retrovirus
Answer: (D) Retrovirus
Explanation: HIV is a retrovirus with an RNA genome. Its reverse transcriptase converts viral RNA into DNA, which can integrate into host-cell chromosomes. Antiretroviral medicines interrupt different stages of the replication cycle and can maintain long-term viral suppression.
Q26. How is yellow fever mainly transmitted?
[Jharkhand PSC Prelims 2013]
(A) Breathing shared indoor air
(B) Drinking contaminated water
(C) Ordinary houseflies
(D) Bites of infected mosquitoes
Answer: (D) Bites of infected mosquitoes
Explanation: Yellow fever is a mosquito-borne viral disease; Aedes aegypti is important in urban cycles, with other mosquitoes involved in sylvatic cycles. It may cause fever, jaundice and bleeding. Vaccination and vector control are central preventive measures.
Q25. Which blood component is commonly reduced during dengue fever?
[UPPSC PCS Prelims 2012]
(A) Platelets
(B) Haemoglobin exclusively
(C) Blood glucose
(D) Calcium
Answer: (A) Platelets
Explanation: Dengue can produce thrombocytopenia through several mechanisms, including altered platelet production and increased destruction or consumption. Platelets support blood clotting. A falling count may prompt monitoring, but severe dengue assessment also requires attention to warning signs and circulation.
Q24. Which viral livestock disease was officially declared eradicated worldwide in 2011?
[UPPSC PCS Prelims 2012]
(A) Foot-and-mouth disease
(B) Rinderpest
(C) Rabies
(D) Cowpox
Answer: (B) Rinderpest
Explanation: Rinderpest, also known as cattle plague, was caused by a morbillivirus affecting cattle and other hoofed animals. Its global eradication was declared in 2011 after vaccination and surveillance campaigns. It became a major example of successful animal-disease eradication.
Q23. What type of pathogen causes AIDS?
[UPPSC PCS Prelims 2011]
(A) Bacterium
(B) Fungus
(C) Virus
(D) Protozoan
Answer: (C) Virus
Explanation: AIDS develops from advanced infection with human immunodeficiency virus. HIV damages the immune system, especially CD4-positive T cells, increasing vulnerability to opportunistic infections. AIDS is the clinical syndrome; HIV is the causative virus.
Q22. Hepatitis B virus belongs to which genome category?
[UPPSC PCS Mains 2011]
(A) DNA virus
(B) RNA-only virus
(C) Bacterium
(D) Parasitic flatworm
Answer: (A) DNA virus
Explanation: Hepatitis B virus has a partially double-stranded DNA genome and replicates via an RNA intermediate using reverse transcription. It differs from hepatitis C, an RNA virus. Chronic hepatitis B may progress to cirrhosis or liver cancer, and vaccination is available.
Q21. Which assertions are correct:
Hepatitis B is more infectious than HIV in relevant blood exposure,
Chronic hepatitis B can cause liver cancer
[UPSC CSE Prelims 2010]
(A) First only
(B) Second only
(C) Both
(D) Neither
Answer: (C) Both
Explanation: Hepatitis B is highly transmissible through certain body-fluid exposures and chronic HBV infection increases the risk of hepatocellular carcinoma. Immunisation, safe injections and screening help reduce risk. HIV is a separate blood-borne and sexually transmissible virus.
Q20. Which statement about swine flu is acceptable?
[UPSC CSE Prelims 2010]
(A) Everyone has identical susceptibility
(B) Antibiotics do not directly treat influenza virus
(C) All pigs must be culled to prevent human spread
(D) Swine flu is caused by Plasmodium
Answer: (B) Antibiotics do not directly treat influenza virus
Explanation: Influenza is viral and cannot be directly cured with antibacterial antibiotics. People differ in vulnerability according to immunity and clinical risk factors. Mass culling of pigs is not an essential general response to human seasonal or pandemic influenza transmission.
Q19. Which claim about HIV transmission is incorrect?
[UPSC CSE Prelims 2010]
(A) Female-to-male sexual transmission is generally twice as likely as male-to-female
(B) Other sexually transmitted infections may increase risk
(C) Transmission can occur during childbirth or breastfeeding
(D) Contaminated transfused blood poses significant risk
Answer: (A) Female-to-male sexual transmission is generally twice as likely as male-to-female
Explanation: Sexual HIV transmission probabilities are not uniform; in typical heterosexual exposure, male-to-female transmission is generally more efficient than the reverse. Other sexually transmitted infections, infected blood products and parent-to-child routes increase risk. Modern preventive treatment can dramatically reduce transmission.
Q18. Which virus is a major cause of severe diarrhoea among infants?
[UPPSC PCS Mains 2010]
(A) Influenza A
(B) Rotavirus
(C) Poliovirus
(D) Rabies virus
Answer: (B) Rotavirus
Explanation: Rotavirus infects the intestinal lining and can cause vomiting, watery diarrhoea and dehydration in young children. Vaccination substantially reduces severe disease. Oral rehydration remains a key supportive treatment for diarrhoeal dehydration regardless of the underlying pathogen.
Q17. Zidovudine, formerly called AZT, is a medication used against which infection?
[Jharkhand PSC Prelims 2010]
(A) Malaria
(B) HIV infection
(C) Tuberculosis
(D) Cholera
Answer: (B) HIV infection
Explanation: Zidovudine is a nucleoside reverse-transcriptase inhibitor historically important in antiretroviral therapy. It interferes with HIV replication rather than directly curing the infection. Modern HIV treatment generally uses combinations of medicines selected according to current clinical guidance.
Q16. Hydrophobia is classically associated with infection by which pathogen type?
[UPPSC PCS Mains 2008]
(A) Bacteria
(B) Fungi
(C) Virus
(D) Protozoan
Answer: (C) Virus
Explanation: Hydrophobia is a classic neurological manifestation of rabies, which is caused by a lyssavirus. After a risky animal bite, immediate wound washing and timely post-exposure prophylaxis can prevent illness. Once classical clinical rabies develops, the disease is almost invariably fatal.
Q15. What kind of organism causes Japanese encephalitis?
[UPPSC PCS Special Prelims 2008]
(A) Bacterium
(B) Virus
(C) Protozoan
(D) Fungus
Answer: (B) Virus
Explanation: Japanese encephalitis virus belongs to the flavivirus group and is transmitted mainly through Culex mosquito bites. Severe cases inflame the brain and may cause lasting neurological problems. Vaccination and reducing mosquito exposure are important in risk areas.
Q14. Separating pigs from settlements can help control transmission of which mosquito-borne disease?
[UPSC CSE Prelims 2007]
(A) Malaria
(B) Japanese encephalitis
(C) Filariasis
(D) Polio
Answer: (B) Japanese encephalitis
Explanation: Pigs are important amplifying hosts in the Japanese encephalitis transmission cycle. Culex mosquitoes can acquire virus from infected animals and infect people, who are usually dead-end hosts. Animal management, mosquito control and vaccination can reduce risk in endemic settings.
Q13. ELISA testing was classically used for screening which viral infection?
[UPPSC PCS Prelims 2007]
(A) Diabetes
(B) Tuberculosis
(C) HIV
(D) Typhoid
Answer: (C) HIV
Explanation: Enzyme-linked immunosorbent assays have long been used in HIV screening by detecting antibodies or antigens, depending on assay generation. Reactive screening results require the appropriate confirmatory testing algorithm. Modern HIV testing also includes rapid and nucleic-acid methods.
Q12. Scientist Robert Webster is especially known for studying which virus?
[UPSC CSE Prelims 2007]
(A) Influenza virus
(B) Rabies virus
(C) Poliovirus
(D) Hepatitis A virus
Answer: (A) Influenza virus
Explanation: Robert G. Webster contributed substantially to understanding influenza viruses, particularly their evolution and emergence from animal reservoirs. Influenza A viruses possess segmented RNA, enabling genetic reassortment. Studying avian and human influenza helps assess pandemic threats.
Q11. Which dengue-related assertion is correct?
[UPSC CSE Prelims 2005]
(A) Dengue is protozoan
(B) Eye pain behind the orbit never occurs
(C) Rash and bleeding can occur in dengue
(D) Culex mosquitoes are the principal vector
Answer: (C) Rash and bleeding can occur in dengue
Explanation: Dengue is viral rather than protozoan, and retro-orbital pain is a recognised symptom. Rash and mucosal bleeding can occur, especially in more serious illness. Aedes mosquitoes are principal vectors; Culex is not the usual dengue vector.
Q10. Which among foot-and-mouth disease, anthrax, black quarter and cowpox are infectious diseases of livestock?
[UPSC CSE Prelims 2005]
(A) First three only
(B) Last three only
(C) First and fourth only
(D) All four
Answer: (D) All four
Explanation: All listed diseases are infectious, although their agents differ. Foot-and-mouth disease and cowpox are viral, whereas anthrax and black quarter are bacterial. Recognising that animal viral disease is part of general biology broadens coverage beyond human infections.
Q9. Which influenza A subtype is popularly associated with avian influenza?
[UPPSC Special Mains 2004]
(A) H5N1
(B) H1N1 exclusively
(C) Zika
(D) HIV-1
Answer: (A) H5N1
Explanation: H5N1 is a subtype of influenza A linked to bird flu outbreaks in poultry and wild birds. The letters specify haemagglutinin and neuraminidase. Surveillance matters because avian influenza viruses sometimes infect mammals, including humans, after relevant exposure.
Q8. Which HIV-1 subtype has historically been predominant in India?
[UPPSC Special Mains 2004]
(A) Subtype A
(B) Subtype B
(C) Subtype C
(D) Subtype D
Answer: (C) Subtype C
Explanation: HIV-1 subtype C has historically accounted for most HIV infections in India. HIV also exhibits substantial genetic diversity, which matters to epidemiology and vaccine research. The subtype classification describes viral genetic lineages, not separate nonviral diseases.
Q7. Which set could all represent manifestations of advanced HIV/AIDS:
enlarged lymph nodes,
night sweats,
memory problems and
weight loss?
[UPSC CSE Prelims 2003]
(A) First two only
(B) Last three only
(C) First, second and third only
(D) All four
Answer: (D) All four
Explanation: Advanced HIV disease can produce persistent lymph-node enlargement, constitutional symptoms, weight loss and neurological impairment. These findings are nonspecific individually, so laboratory testing is needed for diagnosis. Effective treatment can reduce opportunistic illness and improve survival.
Q6. What is a common route by which poliovirus enters the human body?
[Uttarakhand PSC Prelims 2003]
(A) Dog bites
(B) Mosquito bites
(C) Food or water contaminated with faeces
(D) Contact with pollen
Answer: (C) Food or water contaminated with faeces
Explanation: Poliovirus commonly spreads through the faecal–oral route, particularly where sanitation is inadequate. Most infections cause no paralysis, but a small fraction invade the nervous system. Vaccination and improved hygiene are core prevention measures.
Q5. Which disease cannot be cured by routine antibacterial antibiotics?
[RPSC RAS Prelims 2003]
(A) Leprosy
(B) Tetanus
(C) Measles
(D) Cholera
Answer: (C) Measles
Explanation: Measles is caused by a highly contagious virus, so antibiotics do not treat the primary infection. Leprosy, tetanus and cholera have bacterial causes, although their management differs. Vaccination is the key preventive measure against measles.
Q4. Foot-and-mouth disease affecting cloven-hoofed livestock is caused by what?
[UPSC CSE Prelims 2002]
(A) Bacterium
(B) Fungus
(C) Protozoan
(D) Virus
Answer: (D) Virus
Explanation: Foot-and-mouth disease is caused by an aphthovirus of the family Picornaviridae. It spreads rapidly among susceptible cloven-hoofed livestock, including cattle, pigs and sheep. The animal disease should not be confused with human hand, foot and mouth disease.
Q3. Which collection contains only viral diseases?
[Uttarakhand PSC Mains 2002]
(A) Tuberculosis, herpes and rabies
(B) Mumps, rabies and herpes
(C) Cancer, tuberculosis and polio
(D) Chickenpox, cancer and tuberculosis
Answer: (B) Mumps, rabies and herpes
Explanation: Mumps, rabies and herpes are all caused by viruses, although they differ greatly in transmission and affected organs. Tuberculosis is bacterial, and cancer is a broad disease category with many causes. Poliomyelitis and chickenpox are also viral.
Q2. Why does AIDS cause profound immunodeficiency?
[Uttarakhand PSC Mains 2002]
(A) HIV primarily blocks red-cell oxygen carriage
(B) HIV impairs T-helper lymphocytes
(C) HIV converts platelets into fungi
(D) HIV increases skin pigmentation
Answer: (B) HIV impairs T-helper lymphocytes
Explanation: HIV infects and damages CD4-positive T-helper lymphocytes, which coordinate immune responses. Progressive immune injury raises susceptibility to opportunistic infections and certain cancers. CD4 monitoring and antiretroviral viral-load suppression are key concepts in HIV care.
Q1. Ranikhet disease, also known as Newcastle disease, principally affects which animals?
[Uttarakhand PSC Prelims 2002]
(A) Poultry such as chickens
(B) Cattle
(C) Goats only
(D) Horses
Answer: (A) Poultry such as chickens
Explanation: Newcastle disease is an infectious viral disease of birds, especially poultry, caused by avian orthoavulavirus 1. It can spread quickly through flocks and may produce respiratory or neurological signs. Vaccination and poultry biosecurity help control outbreaks.