Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 1131: Which of the following cells are affected by HIV?

A. Only T helper cells
B. T helper cells and macrophages (Correct Answer)
C. NK cells
D. B lymphocytes

Explanation: **Explanation:** The Human Immunodeficiency Virus (HIV) primarily targets cells that express the **CD4 receptor** on their surface. The HIV envelope glycoprotein **gp120** binds specifically to the CD4 molecule to initiate entry. * **Why Option B is Correct:** While **T-helper (CD4+) lymphocytes** are the primary targets and their depletion leads to profound immunosuppression, HIV also infects **macrophages, monocytes, and dendritic cells**. These cells also express CD4 receptors (albeit at lower levels than T-cells) and various co-receptors (CCR5). Macrophages are particularly important as they are resistant to the cytopathic effects of the virus, acting as a **reservoir** for HIV and transporting it to the central nervous system (CNS). * **Why other options are incorrect:** * **Option A:** HIV does not *only* affect T-helper cells; excluding macrophages ignores a critical part of the viral pathogenesis and its persistence in the body. * **Option C & D:** Natural Killer (NK) cells and B lymphocytes do not typically express the CD4 receptor. While B-cell function is often deranged in AIDS (leading to polyclonal hypergammaglobulinemia), this is a secondary effect of the loss of T-helper cell regulation, not a result of direct viral infection. **High-Yield Clinical Pearls for NEET-PG:** * **Co-receptors:** HIV requires co-receptors for entry: **CCR5** (predominant in early infection/macrophage-tropic) and **CXCR4** (seen in late-stage infection/T-cell-tropic). * **Homozygous mutation of CCR5 (CCR5-Δ32)** provides immunity against HIV infection. * **Follicular Dendritic Cells** in the lymph nodes serve as major reservoirs for HIV. * **Microglial cells** are the primary targets of HIV in the brain, leading to HIV-associated dementia.

Question 1132: Which of the following is true about viroids?

A. Lack envelope like covering and have only genetic material (Correct Answer)
B. Have only genetic material
C. Cause tumors in animals and have only genetic material
D. Cause tumors in animals and are visible on light microscope

Explanation: ### **Explanation** **1. Why Option A is Correct:** Viroids are the smallest known infectious agents, consisting solely of a short, circular, single-stranded RNA molecule. Unlike viruses, they **lack a protein coat (capsid)** and an **envelope**. They are essentially "naked" genetic material. The term "viroid" (meaning virus-like) was coined by T.O. Diener to describe these sub-viral pathogens that rely entirely on host cell enzymes for replication. **2. Why Other Options are Incorrect:** * **Option B:** While viroids do have only genetic material, Option A is a more complete description of their structural deficiency (lack of envelope/capsid). * **Option C:** Viroids are exclusively pathogens of **higher plants** (e.g., Potato Spindle Tuber Viroid). They are not known to cause diseases or tumors in animals or humans. (Note: Hepatitis D is a "viroid-like" satellite virus, but it requires a helper virus, HBV, for its envelope). * **Option D:** Viroids are far too small to be seen under a light microscope. They are sub-microscopic and can only be characterized via molecular techniques or electron microscopy. Furthermore, they do not infect animals. **3. High-Yield Clinical Pearls for NEET-PG:** * **Composition:** Circular ssRNA, no protein, no envelope. * **Host:** Exclusively plants. * **Prions vs. Viroids:** Prions are infectious **proteins** (no nucleic acid); Viroids are infectious **nucleic acids** (no protein). * **Hepatitis D Connection:** Often called a "defective virus" or "viroid-like," but it is **not** a true viroid because it possesses a protein coat (HBsAg) borrowed from HBV. * **Replication:** They replicate in the host cell nucleus or chloroplast using the host's RNA polymerase II.

Question 1133: Infectivity of Hepatitis B virus is best diagnosed by which marker?

A. HBeAg (Correct Answer)
B. HBsAg
C. HBV DNA
D. Anti-HBsAg

Explanation: **Explanation:** The infectivity of Hepatitis B Virus (HBV) is primarily determined by the rate of viral replication. **1. Why HBeAg is the correct answer:** **HBeAg (Hepatitis B e-antigen)** is a soluble protein produced during active viral replication. Its presence in the serum serves as a surrogate marker for high viral load and **maximal infectivity**. Clinically, if a patient is HBeAg-positive, they are considered highly infectious (e.g., a high risk of vertical transmission from mother to child). While HBV DNA is a more precise quantitative measure, HBeAg remains the classic diagnostic marker for assessing infectivity in standard examinations. **2. Why other options are incorrect:** * **HBsAg:** This is the first marker to appear and indicates **active infection** (either acute or chronic). However, it does not differentiate between high and low replication states; thus, it is a marker of "infection," not "infectivity." * **HBV DNA:** This is the most sensitive marker for viral replication and is used to monitor treatment. While it correlates with infectivity, in the context of standard MCQ patterns, HBeAg is the established "diagnostic marker" for infectivity. * **Anti-HBsAg:** These are protective antibodies that appear after the disappearance of HBsAg. They indicate **immunity** (via vaccination or recovery) and imply zero infectivity. **High-Yield Clinical Pearls for NEET-PG:** * **Window Period:** The interval where HBsAg and Anti-HBs are both negative; **Anti-HBc IgM** is the only marker present. * **Pre-core Mutant:** A condition where the patient is HBeAg negative but has high HBV DNA levels and high infectivity. * **Best marker of vaccination response:** Anti-HBs titers (>10 mIU/mL). * **First marker to appear:** HBsAg.

Question 1134: Which of the following is not an RNA virus?

A. Hepatitis A
B. Hepatitis B (Correct Answer)
C. Hepatitis C
D. Hepatitis D

Explanation: **Explanation:** The classification of Hepatitis viruses is a high-yield topic for NEET-PG. The correct answer is **Hepatitis B**, as it is the only member of the Hepatitis group that is a **DNA virus**. **1. Why Hepatitis B is the correct answer:** Hepatitis B virus (HBV) belongs to the **Hepadnaviridae** family. It possesses a **partially double-stranded circular DNA** genome. It is unique because it uses an enzyme called **reverse transcriptase** during its replication cycle to convert RNA back into DNA, a feature it shares with retroviruses. **2. Why the other options are incorrect:** * **Hepatitis A (Option A):** A member of the *Picornaviridae* family. It is a non-enveloped, **positive-sense single-stranded RNA (+ssRNA)** virus. * **Hepatitis C (Option C):** A member of the *Flaviviridae* family. It is an enveloped, **+ssRNA** virus. * **Hepatitis D (Option D):** Also known as the "Delta agent," it is a defective **ssRNA** virus that requires the HBsAg (Hepatitis B surface antigen) coat to replicate and cause infection. **Clinical Pearls for NEET-PG:** * **Mnemonic:** All Hepatitis viruses are RNA, **except B** (B = **B**oth strands of DNA, though partially). * **Transmission:** Hepatitis **A** and **E** are transmitted via the **Fecal-Oral** route (Vowels hit the bowels). Hepatitis **B, C, and D** are transmitted parenterally (Blood/Body fluids). * **Hepatitis E:** While it is an RNA virus (*Hepeviridae*), remember it is particularly associated with high mortality in **pregnant women** (fulminant hepatic failure). * **Hepatitis C:** Most common cause of post-transfusion hepatitis and chronic liver disease (cirrhosis/HCC) worldwide.

Question 1135: Which of the following serum markers indicate a super carrier of Hepatitis B Virus (HBV)?

A. HBsAg
B. HBsAg + HBV DNA
C. HBsAg + HBeAg + HBV DNA (Correct Answer)
D. Anti-HBsAg + HBV DNA

Explanation: ### Explanation The term **"Super Carrier"** in Hepatitis B refers to a chronic carrier who is highly infectious. To understand this, we must differentiate between simple carriage and high-level replication. **1. Why Option C is Correct:** A "Super Carrier" is characterized by the presence of three key markers: * **HBsAg (Hepatitis B Surface Antigen):** Indicates the presence of the virus (Chronic state if >6 months). * **HBeAg (Hepatitis B e-Antigen):** This is the hallmark of **active viral replication** and high infectivity. * **HBV DNA:** High levels of viral load in the serum confirm that the virus is actively multiplying. The combination of these three markers signifies that the individual has a high viral load and is most likely to transmit the infection to others (e.g., via needle-stick injuries or vertical transmission). **2. Why Other Options are Incorrect:** * **Option A (HBsAg):** This only indicates that the person is a carrier. It does not specify the level of infectivity or replication. * **Option B (HBsAg + HBV DNA):** While this shows the virus is present and replicating, the absence of **HBeAg** means it doesn't fulfill the classic definition of a "super carrier," as HBeAg is the primary clinical marker for high infectivity. * **Option D (Anti-HBsAg + HBV DNA):** This is a contradictory profile. Anti-HBs indicates immunity/recovery, which usually does not coexist with active HBV DNA (except in rare escape mutants). **3. NEET-PG High-Yield Pearls:** * **Window Period Marker:** Anti-HBc IgM is the only positive marker. * **Best Indicator of Prognosis:** HBV DNA levels. * **Marker of Recovery/Immunity:** Anti-HBs. * **Low Infectivity Carrier:** HBsAg positive but **Anti-HBe** positive (indicates replication has slowed down). * **Pre-core Mutants:** These patients are HBeAg negative but still have high HBV DNA and high infectivity.

Question 1136: A 19-year-old army recruit provides urine and blood samples for further testing. Serum analysis reveals elevated ALT, HBsAg, Anti-HBc, HBeAg, and bilirubin, with all other values being normal. What is the hepatitis B status of this recruit?

A. Asymptomatic carrier
B. Chronic active hepatitis B (Correct Answer)
C. Fulminant hepatitis B
D. Recovered from acute self-limited HBV

Explanation: ### Explanation The correct answer is **Chronic active hepatitis B**. **1. Why the correct answer is right:** The diagnosis is based on the interpretation of the hepatitis B serological markers and liver enzymes: * **HBsAg (+):** Indicates the presence of the virus (either acute or chronic). * **Anti-HBc (+):** In this context, it signifies exposure. Since the patient is a young adult in a high-risk setting (army recruit) and shows signs of active replication, this points toward a persistent infection. * **HBeAg (+):** This is the hallmark of **active viral replication** and high infectivity. * **Elevated ALT & Bilirubin:** These indicate ongoing **hepatocellular necrosis** and inflammation. The combination of persistent viral markers (HBsAg) and biochemical evidence of liver damage (elevated ALT) defines the "active" state of chronic hepatitis B. **2. Why the incorrect options are wrong:** * **Asymptomatic carrier:** While HBsAg would be positive, an asymptomatic carrier typically has **normal ALT levels** and is often HBeAg negative (with Anti-HBe positive), indicating low viral replication and no active liver injury. * **Fulminant hepatitis B:** This presents with severe liver failure, characterized by encephalopathy and significantly deranged coagulation profiles (prolonged PT/INR), which are not mentioned here. * **Recovered from acute HBV:** A recovered patient would be **HBsAg negative** and **Anti-HBs positive**, indicating immunity. **3. NEET-PG High-Yield Pearls:** * **HBeAg** is the best indicator of **infectivity** and replication. * **Anti-HBc IgM** is the sole marker positive during the **"Window Period."** * **Chronic infection** is defined by the persistence of HBsAg for >6 months. * **Ground-glass hepatocytes** on liver biopsy are characteristic of chronic HBV infection.

Question 1137: Hepatitis C virus (HCV) is classified as which of the following?

A. Enveloped RNA virus (Correct Answer)
B. Nonenveloped RNA virus
C. Nonenveloped positive strand RNA virus
D. Enveloped negative strand RNA virus

Explanation: **Explanation:** Hepatitis C Virus (HCV) belongs to the genus *Hepacivirus* within the **Flaviviridae** family. It is characterized as a small, **enveloped**, **single-stranded, positive-sense RNA virus**. 1. **Why Option A is correct:** HCV possesses a lipid envelope derived from the host cell membrane, which contains glycoproteins (E1 and E2) essential for viral entry. Its genetic material is RNA, specifically positive-sense, meaning it can be directly translated into viral proteins by host ribosomes. 2. **Why Options B and C are incorrect:** These options suggest HCV is non-enveloped. Non-enveloped RNA hepatitis viruses include Hepatitis A (HAV) and Hepatitis E (HEV). These are typically transmitted via the fecal-oral route, whereas enveloped viruses like HCV are more fragile and require parenteral transmission (blood/body fluids). 3. **Why Option D is incorrect:** While HCV is enveloped, it is a **positive-strand** RNA virus. Negative-strand RNA viruses (like Influenza or Rabies) must carry their own RNA-dependent RNA polymerase to transcribe a positive strand before translation can occur. **High-Yield Clinical Pearls for NEET-PG:** * **Transmission:** Primarily parenteral (IV drug use is the most common risk factor). * **Chronicity:** HCV has the highest rate of progression to chronic infection (~75-85%) among hepatitis viruses. * **Genotypes:** Genotype 1 is the most common globally; Genotype 3 is highly prevalent in India. * **Diagnosis:** Screening is done via Anti-HCV antibodies; confirmation requires **HCV-RNA PCR** (Gold Standard). * **Treatment:** Managed with Direct-Acting Antivirals (DAAs) like Sofosbuvir, which target non-structural proteins (NS3/4A, NS5A, NS5B).

Question 1138: Fever and hemorrhagic rash are seen in all of the following viral infections EXCEPT:

A. Dengue fever
B. Lassa fever
C. Rift Valley fever
D. Sand fly fever (Correct Answer)

Explanation: **Explanation:** The question tests the ability to differentiate between **Viral Hemorrhagic Fevers (VHFs)** and self-limiting febrile illnesses. **1. Why Sandfly Fever is the correct answer:** Sandfly fever (also known as Pappataci fever), caused by the *Phlebovirus* (transmitted by *Phlebotomus papatasi*), is a self-limiting, influenza-like illness. While it presents with sudden onset high fever, severe retro-orbital pain, and conjunctival injection, it is **not** associated with a hemorrhagic rash or bleeding manifestations. It typically resolves within 3–4 days without major complications. **2. Analysis of Incorrect Options:** * **Dengue Fever:** Caused by the *Flavivirus*, it is a classic cause of hemorrhagic manifestations. Severe forms (Dengue Hemorrhagic Fever) present with thrombocytopenia, petechiae, ecchymosis, and gastrointestinal bleeding. * **Lassa Fever:** An Arenavirus endemic to West Africa. It is a notorious cause of VHF, characterized by multi-organ failure, mucosal bleeding, and a high fatality rate. * **Rift Valley Fever:** Like Sandfly fever, it is a *Phlebovirus*, but unlike Sandfly fever, it can progress to severe disease including ocular disease, encephalitis, and a fatal hemorrhagic syndrome with jaundice and hematemesis. **Clinical Pearls for NEET-PG:** * **VHF Families:** Remember the four main families: *Flaviviridae* (Dengue, Yellow Fever), *Filoviridae* (Ebola, Marburg), *Arenaviridae* (Lassa), and *Bunyaviridae* (Crimean-Congo, Rift Valley). * **Sandfly Fever Key Sign:** **Pick’s Sign** (deep erythema of the conjunctivae and face) is a characteristic finding, but it is not a hemorrhagic rash. * **Vector Check:** Sandfly is the vector for both Leishmaniasis (Protozoa) and Sandfly fever (Virus).

Question 1139: Which of the following is a RNA virus?

A. Measles virus (Correct Answer)
B. Herpes virus
C. Papaya mosaic virus
D. Adenovirus

Explanation: **Explanation:** The classification of viruses into DNA or RNA types is a fundamental concept in microbiology and a high-yield topic for NEET-PG. **Correct Answer: A. Measles virus** Measles virus belongs to the **Paramyxoviridae** family. It is a single-stranded, negative-sense, non-segmented **RNA virus**. It is characterized by its helical nucleocapsid and an envelope containing hemagglutinin (H) and fusion (F) proteins, but notably lacks neuraminidase. **Analysis of Incorrect Options:** * **B. Herpes virus:** This is a member of the *Herpesviridae* family, which consists of large, enveloped, **double-stranded DNA (dsDNA)** viruses with icosahedral symmetry. * **C. Papaya mosaic virus:** While this is an RNA virus (Potexvirus), in the context of medical exams like NEET-PG, the focus is on **human pathogens**. Furthermore, the question likely intended to list a common DNA virus or was a distractor; however, among the options provided, Measles is the primary human RNA pathogen of clinical significance. * **D. Adenovirus:** This is a non-enveloped, **double-stranded DNA (dsDNA)** virus known for causing respiratory infections, conjunctivitis (pink eye), and gastroenteritis. **Clinical Pearls for NEET-PG:** * **Mnemonic for DNA Viruses:** "**HHAPPPPy**" (Herpes, Hepadna, Adeno, Papilloma, Polyoma, Pox, Parvo). Note: All are dsDNA except Parvo (ssDNA). * **Measles (Rubeola):** Look for the "3 Cs" (Cough, Coryza, Conjunctivitis) and **Koplik spots** (pathognomonic buccal lesions). * **Vitamin A:** Supplementation is crucial in Measles management to reduce morbidity and mortality. * **SSPE:** Subacute sclerosing panencephalitis is a dreaded late complication of Measles caused by a persistent mutant virus in the CNS.

Question 1140: All of the following are true about poliovirus, except -

A. Type I is responsible for most epidemics
B. Type I is very difficult to eliminate
C. Type I is responsible for vaccine-associated paralytic poliomyelitis (Correct Answer)
D. Type I is most commonly associated with paralysis

Explanation: ### Explanation Poliovirus is a single-stranded RNA enterovirus with three distinct serotypes (1, 2, and 3). Understanding the epidemiological differences between these types is crucial for NEET-PG. **Why Option C is the correct answer (The False Statement):** Vaccine-associated paralytic poliomyelitis (VAPP) is primarily caused by **Type 3** and **Type 2** strains found in the Oral Polio Vaccine (OPV). Type 3 is the most common cause of VAPP among vaccine recipients, while Type 2 was the most frequent cause of outbreaks derived from circulating vaccine-derived polioviruses (cVDPV) before its global eradication and removal from the trivalent vaccine. Type 1 is the least likely to cause VAPP. **Analysis of Incorrect Options (True Statements):** * **Option A & D:** **Type 1 (Brunhilde)** is the most virulent and highly ketogenic strain. It is responsible for the vast majority of paralytic polio cases and most major epidemics worldwide. * **Option B:** Because Type 1 is highly infectious and remains the only wild poliovirus (WPV1) still circulating globally (endemic in Pakistan and Afghanistan), it is considered the most difficult to eliminate compared to Type 2 (eradicated in 1999) and Type 3 (eradicated in 2012). **High-Yield Clinical Pearls for NEET-PG:** * **Specimen of choice:** Stool is the best sample for virus isolation (maximum excretion occurs in the first 2 weeks). * **Most common presentation:** Asymptomatic/Inapparent infection (90–95%). * **Paralytic Polio:** Occurs in <1% of infections; characterized by asymmetrical, flaccid paralysis with preserved sensory functions. * **Vaccine Shift:** India switched from tOPV to bOPV (containing only Type 1 and 3) in 2016 to eliminate the risk of Type 2 VDPV.

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Virology — MCQs

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