Free Viruses MCQs with Answers

31. Which of the following body fluids is NOT normally an effective vehicle for transmitting HIV?

• A. Blood
• B. Saliva
• C. Semen
• D. Vaginal secretions

Explanation: Blood, semen and vaginal secretions carry enough virus to transmit infection, but saliva contains too little and is even mildly antiviral. This is why sharing meals or kissing does not spread HIV, an important fact for removing stigma.

32. The provirus stage of HIV refers to

• A. free virus particles circulating in the plasma
• B. virus crystals stored in lymph nodes
• C. viral DNA integrated into the chromosome of the host cell
• D. the inactive form of the virus outside the body

Explanation: Once reverse transcriptase makes the DNA copy, integrase inserts it into the host genome, where it can stay silent for years or direct the production of new virus. Integration is what makes the infection permanent and hard to cure.

33. No effective vaccine against HIV has yet been produced mainly because

• A. the virus is too large for the immune system
• B. HIV infects only animals
• C. antibodies can never form against HIV
• D. the virus mutates its envelope proteins very rapidly

Explanation: The envelope glycoproteins change faster than a vaccine can be designed, and the virus hides inside cells as a provirus. Antibodies do form in infection, but they keep chasing a moving target, which is the real obstacle.

34. A positive ELISA screening result for HIV is usually confirmed by

• A. repeating the ELISA only
• B. the Western blot technique
• C. a blood culture on agar
• D. a chest X ray

Explanation: ELISA is sensitive but can give false positives, so Western blot, which separates the viral proteins and shows which antibodies are present, is used to confirm. Viruses cannot be cultured on ordinary agar, ruling that option out entirely.

35. A mother infected with HIV can pass the virus to her child

• A. during pregnancy, during delivery and through breastfeeding
• B. only through the genes she passes on
• C. only if the child is vaccinated
• D. never, since HIV requires a needle to spread

Explanation: Mother to child transmission can occur across the placenta, at birth and in breast milk, which is why antiretroviral treatment during pregnancy sharply cuts the risk. HIV is never inherited through genes, since it infects cells rather than the germ line.

36. Which everyday contact does NOT transmit HIV?

• A. Sharing needles contaminated with infected blood
• B. Sexual contact with an infected person
• C. Transfusion of infected blood
• D. Sharing a meal with an infected person

Explanation: HIV needs direct access to blood or mucous membranes, so casual contact such as meals, handshakes and sneezing carries no risk. Knowing this is essential both for prevention and for ending the isolation of infected people.

37. Combination antiretroviral therapy uses several drugs at the same time because

• A. single drugs are too expensive to manufacture
• B. the drugs increase each other's side effects
• C. HIV develops resistance rapidly to any single drug
• D. they kill the virus directly by oxidation

Explanation: HIV mutates so fast that a population resistant to one drug soon appears, but becoming resistant to three at once is far harder. That is why cocktail therapy suppresses the virus for years even though it cannot eliminate the provirus.

38. HIV is classified within which subgroup of retroviruses?

• A. Oncoviruses
• B. Lentiviruses
• C. Spumaviruses
• D. Adenoviruses

Explanation: Lentiviruses, meaning slow viruses, cause long incubation, persistent infections, which fits HIV's years long course from infection to AIDS. Oncoviruses cause cancers and adenoviruses are DNA viruses, so neither group contains HIV.

39. Blood banks test every donated unit of blood for HIV primarily to

• A. prevent transmission of the virus through transfusion
• B. increase the storage life of the blood
• C. raise the red cell count of the unit
• D. detect anaemia in the donor

Explanation: One unit of infected blood can transmit HIV directly into the recipient's circulation, so screening donated blood is one of the most effective barriers to spread. The tests used have nothing to do with storage or cell counts.

40. The envelope glycoprotein gp120 of HIV is important because it

• A. makes vaccination unnecessary
• B. destroys the host's red blood cells
• C. binds to receptors on host cells and allows the virus to enter
• D. makes the virus resistant to heat

Explanation: gp120 projects from the envelope and locks onto CD4 receptors, the first step of infection, which is why it is also the main target researchers aim antibodies at. It has no role against heat or red cells.