Virology Practice Questions

Q: Hand, foot, and mouth disease is caused by which virus?

Enterovirus 71. **Explanation:** **Hand, Foot, and Mouth Disease (HFMD)** is a common viral illness, primarily affecting children, characterized by fever and vesicular eruptions on the palms, soles, and oral mucosa. **1. Why Enterovirus 71 is correct:** HFMD is most commonly caused by viruses belonging to the *Picornaviridae* family, specifically the genus *Enterovirus*. The two most frequent causative agents are **Coxsackievirus A16** (the most common cause globally) and **Enterovirus 71 (EV-71)**. EV-71 is particularly significant in medical exams because it is associated with more severe clinical manifestations, including neurological complications like aseptic meningitis, encephalitis, and acute flaccid paralysis. **2. Why the other options are incorrect:** * **Enterovirus 70:** This virus is the primary cause of **Acute Hemorrhagic Conjunctivitis (AHC)**, often occurring in large epidemics. * **Enterovirus 72:** This was the former taxonomic designation for **Hepatitis A virus**. It causes acute infectious hepatitis, not vesicular skin rashes. * **Enterovirus 68:** This is primarily a **respiratory pathogen** associated with severe lower respiratory tract infections and, occasionally, acute flaccid myelitis (AFM) in children. **Clinical Pearls for NEET-PG:** * **Transmission:** Fecal-oral route and respiratory droplets. * **Clinical Triad:** Ulcers in the mouth (herpangina-like) + Maculopapular/vesicular rash on hands and feet. * **Complications:** While Coxsackie A16 is usually self-limiting, **EV-71** is the high-yield "danger" subtype linked to brainstem encephalitis and pulmonary edema. * **Differential Diagnosis:** Do not confuse HFMD with "Foot and Mouth Disease" (Aphthovirus), which affects cattle and rarely humans.

Q: Which of the following viruses, in addition to HSV-1 and HSV-2, produces the cytopathologic finding of multinucleated giant cells?

Varicella-zoster virus. **Explanation:** The hallmark cytopathologic finding for certain herpesviruses is the formation of **multinucleated giant cells** with intranuclear inclusion bodies (Cowdry type A). This occurs due to the fusion of infected host cell membranes, a process mediated by viral glycoproteins. **Why Varicella-zoster virus (VZV) is correct:** VZV, like HSV-1 and HSV-2, belongs to the **Alphaherpesvirinae** subfamily. These viruses share the characteristic of inducing cell-to-cell fusion (syncytia). A **Tzanck smear** performed on scrapings from the base of a vesicle will show these characteristic multinucleated giant cells in infections caused by HSV-1, HSV-2, and VZV. **Why other options are incorrect:** * **Adenovirus:** Typically produces "smudge cells" (large, dark intranuclear inclusions) but does not form multinucleated giant cells. * **Cytomegalovirus (CMV):** While it causes cell enlargement (cytomegaly), its classic finding is a single, large "Owl’s eye" intranuclear inclusion. It does not typically present with multinucleation on a Tzanck smear. * **Human papillomavirus (HPV):** Characterized by **koilocytes** (squamous epithelial cells with perinuclear halos and wrinkled nuclei), not multinucleated giant cells. **High-Yield NEET-PG Pearls:** * **Tzanck Smear:** Used for rapid bedside diagnosis of HSV and VZV. It identifies multinucleated giant cells but *cannot* distinguish between HSV-1, HSV-2, and VZV. * **Cowdry Type A Inclusions:** Eosinophilic nuclear inclusions surrounded by a clear halo; seen in HSV and VZV. * **Syncytia Formation:** Also a key feature of Paramyxoviruses (like Measles and RSV) and HIV, but in the context of vesicular skin rashes, always think of the Alpha-herpes family.

Q: A child who has undergone a kidney transplant develops lymphoproliferative cancer. This is associated with which viral infection?

Epstein-Barr virus (EBV). **Explanation:** The correct answer is **Epstein-Barr virus (EBV)**. This condition is known as **Post-Transplant Lymphoproliferative Disorder (PTLD)**. **Why EBV is correct:** In transplant recipients, the administration of potent immunosuppressive drugs (to prevent graft rejection) leads to a significant reduction in **T-cell mediated immunity**. EBV naturally infects B-lymphocytes and remains latent. Without T-cell surveillance (specifically Cytotoxic T-lymphocytes), EBV-infected B-cells undergo uncontrolled proliferation, driven by viral oncogenes like **LMP-1**. This can progress from benign polyclonal B-cell hyperplasia to malignant monoclonal B-cell lymphoma. **Why other options are incorrect:** * **Cytomegalovirus (CMV):** While CMV is the most common viral infection post-transplant, it typically causes fever, pneumonia, or retinitis, rather than lymphoproliferative cancer. * **Varicella-zoster virus (VZV):** Causes chickenpox or shingles. In transplant patients, it can lead to disseminated disease, but it is not oncogenic. * **Human papillomavirus (HPV):** Associated with cervical, anogenital, and oropharyngeal cancers, but not typically with systemic lymphoproliferative disorders in the context of acute post-transplant immunosuppression. **High-Yield NEET-PG Pearls:** * **EBV Association:** Also linked to Burkitt Lymphoma (t(8;14)), Nasopharyngeal Carcinoma, and Hodgkin Lymphoma. * **PTLD Management:** The first step in management is often the **reduction of immunosuppressive therapy** to allow the patient’s immune system to regain control over the B-cell proliferation. * **Diagnosis:** Elevated EBV viral load (via PCR) and biopsy showing B-cell expansion (CD20+).

Q: Which of the following statements regarding Hepatitis B virus (HBV) and Hepatitis D virus (HDV) is false?

Both are DNA viruses. **Explanation:** The correct answer is **D** because it is a factually incorrect statement. **Hepatitis B Virus (HBV)** is a partially double-stranded **DNA virus** (Hepadnaviridae), whereas **Hepatitis D Virus (HDV)** is a defective **RNA virus**. HDV requires the surface antigen (HBsAg) of HBV to provide its envelope for assembly and transmission. **Analysis of other options:** * **Option A (Both can infect simultaneously):** This is true and is termed **Co-infection**. It typically presents as acute hepatitis and often results in recovery, with a low risk of chronicity. * **Option B (HDV causes more serious infection due to superinfection):** This is true. **Superinfection** occurs when a chronic HBV carrier is later infected with HDV. This leads to a much higher risk of fulminant hepatitis, rapid progression to cirrhosis, and a high rate of chronic HDV infection. * **Option C (HDV cannot infect in the absence of HBV):** This is true. HDV is a "satellite" or defective virus; it lacks the genes to produce its own coat protein and must "borrow" HBsAg from HBV to infect other cells. **High-Yield Clinical Pearls for NEET-PG:** * **HBV Genome:** Circular, partially double-stranded DNA; replicates via **Reverse Transcriptase**. * **HDV Genome:** Single-stranded, circular, negative-sense RNA. It is the smallest known human virus. * **Serology:** In co-infection, both IgM anti-HBc and IgM anti-HDV are present. In superinfection, only IgM anti-HDV is present (IgG anti-HBc will be present as the patient is a chronic carrier). * **Prevention:** The HBV vaccine automatically protects against HDV because HDV cannot exist without HBV.

Q: A 35-year-old male patient presented with a history of jaundice for 15 days. The onset was preceded by a prodromal illness. His serum tested positive for HBsAg. A clinical diagnosis of acute Hepatitis B was made. What should be the next best confirmatory investigation?

Anti-HBeAg antibody. **Explanation** In the clinical scenario of acute Hepatitis B, the diagnosis is typically established by the presence of **HBsAg** and **IgM anti-HBc**. However, to confirm active viral replication and assess the patient's infectivity status, the detection of the **HBeAg (Hepatitis B e-antigen)** or its corresponding antibody is crucial. **Why Option A is Correct:** The question asks for the "next best confirmatory investigation" following an HBsAg positive result in an acute setting. **Anti-HBc IgM** (often referred to in shorthand or specific contexts as the core antibody) is the gold standard for confirming **acute** infection, especially during the "window period" when HBsAg may have disappeared but Anti-HBs has not yet appeared. In the context of the provided options, testing for the core antibody components is the standard protocol to differentiate acute from chronic infection. **Why Incorrect Options are Wrong:** * **B. HBeAg:** While it indicates high infectivity and active replication, it is not a "confirmatory" marker for the diagnosis of acute hepatitis itself; it is a marker of viral load. * **C. Anti-HBe IgM antibody:** This is a distractor. There is no specific "IgM" version of the anti-HBe antibody used in clinical practice; IgM is specific to the **Anti-HBc** (Core) antibody. * **D. HBV DNA by PCR:** While this is the most sensitive marker for viral quantification, it is generally reserved for monitoring treatment response in chronic cases or resolving diagnostic dilemmas, rather than the initial confirmation of acute Hepatitis B. **Clinical Pearls for NEET-PG:** * **Window Period:** The period where HBsAg is negative and Anti-HBs is not yet positive. The only marker present is **IgM Anti-HBc**. * **HBsAg:** First marker to appear in blood (even before symptoms). * **Anti-HBs:** Indicates immunity (via recovery or vaccination). * **HBeAg:** Indicates high transmissibility ("e" for envelope/infectivity).

Q: Which one of the following mosquitoes transmits West Nile fever?

Culex. **Explanation:** **West Nile Virus (WNV)** is a member of the *Flaviviridae* family (genus Flavivirus) and is the causative agent of West Nile fever. The virus is maintained in a **bird-mosquito-bird** transmission cycle. 1. **Why Culex is correct:** The primary vectors for West Nile Virus are mosquitoes of the genus **Culex** (specifically *Culex pipiens*, *C. quinquefasciatus*, and *C. tarsalis*). These mosquitoes act as the bridge vector, carrying the virus from the primary reservoir (birds) to incidental hosts like humans and horses. Humans are considered **"dead-end hosts"** because they do not develop high enough viral titers in their blood to re-infect mosquitoes. 2. **Why other options are incorrect:** * **Anopheles:** Primarily known as the vector for **Malaria**. * **Aedes:** The principal vector for other Flaviviruses like **Dengue, Zika, and Yellow Fever**, as well as the Togavirus **Chikungunya**. * **Mansonoides:** Known for transmitting **Brugian Filariasis** (*Brugia malayi*). **High-Yield Clinical Pearls for NEET-PG:** * **Reservoir:** Wild birds (Passerines/songbirds). * **Clinical Spectrum:** Most infections are asymptomatic (80%). About 20% develop West Nile Fever (flu-like symptoms), and <1% develop **Neuroinvasive disease** (Meningitis, Encephalitis, or Acute Flaccid Paralysis). * **Diagnosis:** Detection of **IgM antibodies** in serum or CSF via MAC-ELISA is the gold standard. * **Other Culex-transmitted diseases:** Japanese Encephalitis (JE) and Bancroftian Filariasis (*Wuchereria bancrofti*).

Q: An infant presents with fever and persistent cough. Physical examination and a chest x-ray suggest pneumonia. Which of the following is most likely the cause of this infection?

Respiratory syncytial virus. **Explanation:** The clinical presentation of fever, persistent cough, and pneumonia in an infant is a classic description of **Respiratory Syncytial Virus (RSV)** infection. RSV is the most common cause of lower respiratory tract infections (LRTI), including bronchiolitis and pneumonia, in infants and children under the age of one. It belongs to the *Paramyxoviridae* family and is characterized by the formation of syncytia (multinucleated giant cells) in host tissues. **Analysis of Options:** * **Respiratory Syncytial Virus (Correct):** It is the leading cause of viral pneumonia in infants. The small diameter of infant airways makes them highly susceptible to the inflammation and mucus plugging caused by RSV. * **Rotavirus:** This is the most common cause of severe diarrhea and dehydration in infants and young children worldwide, not respiratory infections. * **Adenovirus:** While it can cause pneumonia (Types 3, 7, 21), it more commonly presents with pharyngoconjunctival fever or hemorrhagic cystitis. It is a less frequent cause of infant pneumonia compared to RSV. * **Coxsackievirus:** A member of the *Picornaviridae* family, it typically causes Hand-Foot-and-Mouth disease, herpangina, or myocarditis, rather than primary pneumonia in infants. **High-Yield Clinical Pearls for NEET-PG:** * **RSV Seasonality:** Typically peaks during winter months. * **Diagnosis:** Rapid antigen detection tests or RT-PCR from nasopharyngeal swabs are the gold standards. * **Radiology:** Chest X-rays often show hyperinflation and peribronchial thickening. * **Treatment:** Primarily supportive; **Ribavirin** (aerosolized) may be used in severe cases or immunocompromised patients. **Palivizumab** (monoclonal antibody) is used for prophylaxis in high-risk preterm infants.

Q: Which of the following statements about the influenza A virus is true?

Hemagglutinin and neuraminidase are strain-specific.. **Explanation:** **1. Why Option D is Correct:** The influenza A virus is classified into subtypes based on its surface glycoproteins: **Hemagglutinin (H)** and **Neuraminidase (N)**. These proteins are highly variable and undergo frequent mutations. Because they are the primary targets of the host immune response, the specific combination and structure of H and N define the particular **strain** (e.g., H1N1, H3N2). Antibodies against these surface antigens provide immunity only to that specific strain. **2. Why the Other Options are Incorrect:** * **Option A:** Influenza A belongs to the *Orthomyxoviridae* family. It has a **single-stranded**, negative-sense, segmented RNA genome (8 segments), not double-stranded. * **Option B:** Pandemics are caused by **Antigenic Shift**, which involves a major genetic reassortment leading to a completely new subtype. **Antigenic Drift** (point mutations) causes seasonal epidemics. * **Option C:** The **Nucleocapsid (NP)** and Matrix (M1) proteins are the internal type-specific antigens used to differentiate Influenza A, B, and C. They are **relatively stable** and do not vary between strains of the same type; therefore, NP antibodies are type-specific but **not strain-specific**. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Shift:** Seen only in Influenza A (due to its wide animal reservoir). * **Hemagglutinin (H):** Responsible for cell attachment (via sialic acid receptors) and agglutination of RBCs. * **Neuraminidase (N):** Facilitates the release of progeny virions from infected cells; inhibited by **Oseltamivir**. * **Amantadine/Rimantadine:** Act by inhibiting the **M2 ion channel** (only effective against Influenza A).

Q: Which of the following viruses is labile to acid but heat stable?

Rhinovirus. **Explanation:** The correct answer is **Rhinovirus**. This question tests the fundamental differentiation between genera within the *Picornaviridae* family based on physical properties. **1. Why Rhinovirus is correct:** Rhinoviruses are the primary cause of the common cold. A defining characteristic of Rhinoviruses is their **acid lability** (they are inactivated at a pH < 5.0–6.0). This property prevents them from surviving the acidic environment of the stomach, which is why they primarily infect the upper respiratory tract rather than the gastrointestinal tract. Conversely, they are relatively **heat stable**, surviving for long periods on environmental surfaces at room temperature, which facilitates transmission via fomites. **2. Why the other options are incorrect:** * **Options A, B, and C (Enteroviruses):** Human enterovirus 70, 68, and Echoviruses all belong to the genus *Enterovirus*. Unlike Rhinoviruses, Enteroviruses are **acid-stable** (resistant to pH 3.0). This allows them to pass through the stomach unharmed and colonize the intestine. While they are also relatively stable at room temperature, the distinguishing factor in this question is their resistance to acid. **High-Yield Clinical Pearls for NEET-PG:** * **Temperature Preference:** Rhinoviruses grow best at **33°C** (the temperature of the nasal mucosa) rather than 37°C (body temperature). * **Receptor:** Most Rhinoviruses (90%) use **ICAM-1** (CD54) as their cellular receptor. * **Transmission:** Hand-to-eye or hand-to-nose contact via contaminated surfaces is more common than aerosol transmission. * **Vaccination:** No vaccine is available due to the existence of over 100 distinct serotypes.

Q: Which disease is characterized by the presence of Torres bodies in the liver cells in its early stage?

Yellow fever. **Explanation:** The correct answer is **Yellow Fever**. **Yellow Fever** is a viral hemorrhagic fever caused by a Flavivirus. The virus is hepatotropic, leading to significant liver pathology. **Torres bodies** are characteristic acidophilic (eosinophilic) intranuclear inclusion bodies found in hepatocytes during the early stages of the disease. As the disease progresses, these are often accompanied by **Councilman bodies**, which represent apoptotic, eosinophilic degeneration of hepatocytes. **Analysis of Incorrect Options:** * **Kala-azar (Visceral Leishmaniasis):** Caused by *Leishmania donovani*, it is characterized by the presence of **LD bodies** (Leishman-Donovan bodies), which are amastigote forms found within macrophages, not Torres bodies. * **Q Fever:** Caused by *Coxiella burnetii*, the classic liver finding is a **"doughnut granuloma"** (a fibrin-ring granuloma), not intranuclear inclusions. * **Lymphogranuloma venereum (LGV):** Caused by *Chlamydia trachomatis* (serotypes L1-L3), it is characterized by **Gamna-Favre bodies** (large intracytoplasmic inclusions) within lymph nodes, typically presenting as the "Groove sign." **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Aedes aegypti* mosquito is the primary vector. * **Councilman Bodies:** Though seen in Yellow Fever, they are not pathognomonic as they can also appear in viral hepatitis. * **Vaccine:** The **17D vaccine** is a live-attenuated vaccine providing immunity for life (International Certificate of Vaccination is valid starting 10 days after vaccination). * **Faget’s Sign:** A clinical hallmark of Yellow Fever where there is **relative bradycardia** despite a high fever.

Question 1

Hand, foot, and mouth disease is caused by which virus?

Accepted Answer

Enterovirus 71

Answer

Enterovirus 70

Answer

Enterovirus 72

Answer

Enterovirus 68

Question 2

Which of the following viruses, in addition to HSV-1 and HSV-2, produces the cytopathologic finding of multinucleated giant cells?

Accepted Answer

Varicella-zoster virus

Answer

Adenovirus

Answer

Cytomegalovirus

Answer

Human papillomavirus

Question 3

A child who has undergone a kidney transplant develops lymphoproliferative cancer. This is associated with which viral infection?

Accepted Answer

Epstein-Barr virus (EBV)

Answer

Cytomegalovirus (CMV)

Answer

Varicella-zoster virus (VZV)

Answer

Human papillomavirus (HPV)

Question 4

Which of the following statements regarding Hepatitis B virus (HBV) and Hepatitis D virus (HDV) is false?

Accepted Answer

Both are DNA viruses

Answer

Both can infect simultaneously

Answer

HDV causes more serious infection due to superinfection

Answer

HDV cannot infect in the absence of HBV

Question 5

A 35-year-old male patient presented with a history of jaundice for 15 days. The onset was preceded by a prodromal illness. His serum tested positive for HBsAg. A clinical diagnosis of acute Hepatitis B was made. What should be the next best confirmatory investigation?

Accepted Answer

Anti-HBeAg antibody

Answer

HBe antigen

Answer

Anti-HBe IgM antibody

Answer

HBV DNA by PCR

Question 6

Which one of the following mosquitoes transmits West Nile fever?

Accepted Answer

Culex

Answer

Anopheles

Answer

Aedes

Answer

Mansonoides

Question 7

An infant presents with fever and persistent cough. Physical examination and a chest x-ray suggest pneumonia. Which of the following is most likely the cause of this infection?

Accepted Answer

Respiratory syncytial virus

Answer

Rotavirus

Answer

Adenovirus

Answer

Coxsackievirus

Question 8

Which of the following statements about the influenza A virus is true?

Accepted Answer

Hemagglutinin and neuraminidase are strain-specific.

Answer

It has a double-stranded segmented RNA genome.

Answer

Pandemics are caused by antigenic drift.

Answer

Nucleocapsid antibody is not strain-specific.

Question 9

Which of the following viruses is labile to acid but heat stable?

Accepted Answer

Rhinovirus

Answer

Human enterovirus serotype 70

Answer

Human enterovirus serotype 68

Answer

Echovirus

Question 10

Which disease is characterized by the presence of Torres bodies in the liver cells in its early stage?

Accepted Answer

Yellow fever

Answer

Kala-azar

Answer

Q fever

Answer

Lymphogranuloma venereum (LGV)

Virology — MCQs

Virology — MCQs

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