Virology Practice Questions

Q: Receptor used for the entry of HIV virus into the host cell is?

CCR5. ***CCR5*** - HIV initially binds to the **CD4** receptor on the surface of T-helper cells, which triggers a conformational change in the viral envelope protein gp120. - This change exposes a binding site for a coreceptor, which is typically the chemokine receptor **CCR5** (or **CXCR4**), facilitating the fusion of the viral envelope with the host cell membrane and allowing viral entry. *CCR7* - **CCR7** is a chemokine receptor primarily involved in the homing of lymphocytes and dendritic cells to secondary lymphoid organs like lymph nodes. - It is not utilized by HIV as a coreceptor for entry into host cells. *CD6* - **CD6** is a cell surface receptor found on T cells that functions as a costimulatory molecule in T-cell activation and adhesion. - It plays no role in the binding or entry process of the HIV virus. *CD8* - **CD8** is a coreceptor molecule that defines cytotoxic T lymphocytes, which are essential for killing virally infected cells. - HIV primarily infects **CD4+** cells, not CD8+ cells, and CD8 does not serve as a viral entry receptor.

Q: A child was brought with c/o multiple lesions. O/E multiple vesicular lesions are seen on the palms, soles, and oral mucosa. Which of the following is the most likely etiological agent causing the disease?

Coxsackie virus. ***Coxsackie virus*** - The clinical presentation of vesicular lesions on the **palms**, **soles**, and **oral mucosa** is the classic triad for **Hand, Foot, and Mouth Disease (HFMD)**. - **Coxsackievirus A16** and **Enterovirus 71** are the most common causes of HFMD, a typically self-limiting illness in young children that spreads via fecal-oral or respiratory routes. *Varicella-zoster virus* - This virus causes **chickenpox**, which presents as a generalized, pruritic, vesicular rash in various stages of healing, typically starting on the **trunk** and spreading centrifugally. - The characteristic distribution of chickenpox is **centripetal**, and prominent involvement of palms and soles is uncommon. *Measles virus* - Measles presents with **maculopapular rash** that begins on the face and spreads cephalocaudally, accompanied by the **3 Cs** (cough, coryza, conjunctivitis) and **Koplik spots** on the buccal mucosa. - The rash is **not vesicular** and typically **spares the palms and soles**, unlike HFMD. *Human-herpesvirus 6* - HHV-6 is the cause of **roseola infantum** (exanthem subitum), characterized by a high fever that resolves, followed by a blanching **maculopapular rash** on the trunk. - Roseola does not cause vesicular lesions and characteristically **spares the palms and soles**.

Q: A patient is positive for HBsAg and anti-HBc IgM. What is the most likely diagnosis?

Acute hepatitis. ***Acute hepatitis***- The simultaneous presence of **HBsAg** (Hepatitis B surface antigen) indicates active infection [1], paired with **anti-HBc IgM** (Immunoglobulin M against the core antigen) [2].- **Anti-HBc IgM** is the serological hallmark of a recent or **acute** Hepatitis B infection, typically detectable for up to 6 months after symptom onset [1].*Chronic hepatitis*- Chronic infection is defined by the persistence of **HBsAg** for **more than six months** [1].- The predominant core antibody present in chronic infection is **anti-HBc IgG**, whereas Anti-HBc IgM becomes undetectable [1].*Recovery phase*- The recovery phase is marked by the presence of **anti-HBs** (Hepatitis B surface antibody), indicating clearance of the virus and protective immunity [1].- During recovery, **HBsAg** is negative, and **anti-HBc IgM** is absent, leaving only **anti-HBc IgG** and anti-HBs [1].*Vaccination*- Successful vaccination only produces immunity against the surface antigen, resulting solely in the presence of **anti-HBs** [1].- Both **HBsAg** and **anti-HBc** (IgM or IgG) are universally negative following vaccination [1].

Q: Which of the following hepatitis viruses is likely to get transmitted via fecal-oral route?

Hepatitis A. ***Hepatitis A***- Hepatitis A virus (HAV) is primarily spread through the **fecal-oral route**, typically via consumption of food or water contaminated with feces.- It causes an **acute**, self-limiting infection that rarely results in chronic liver disease.*Hepatitis B*- Hepatitis B virus (HBV) is transmitted mainly through **parenteral** (exposure to infected blood), sexual contact, or perinatal (mother-to-child) routes.- Unlike HAV, HBV is a major cause of **chronic hepatitis**, cirrhosis, and hepatocellular carcinoma.*Hepatitis C*- Hepatitis C virus (HCV) transmission is predominantly **parenteral**, most commonly associated with intravenous drug use, blood transfusions (historically), and shared needles.- HCV is the leading cause of chronic viral hepatitis globally and frequently establishes persistent infection.*Hepatitis D*- Hepatitis D virus (HDV) is a defective RNA virus that requires **Hepatitis B surface antigen (HBsAg)** for its replication and assembly.- HDV is transmitted parenterally (same routes as HBV) and not via the fecal-oral route.

Q: The image shown here is used for the diagnosis of

Herpes simplex virus. ***Herpes simplex virus*** - The image is a transmission electron micrograph showing multiple enveloped virions with a characteristic dense central core and an icosahedral nucleocapsid, giving a "target" or "bull's-eye" appearance. - This morphology is a classic feature of the **Herpesviridae** family, which includes Herpes Simplex Virus (HSV), Varicella-Zoster Virus (VZV), and Cytomegalovirus (CMV). *Human immunodeficiency virus* - HIV is a **retrovirus**, and its mature virion has a distinct **cone-shaped** or **bar-shaped** core, which is morphologically different from the spherical, target-like core shown in the image. - The primary diagnostic methods for HIV are serological assays (e.g., **ELISA**) and nucleic acid tests (**PCR**), not electron microscopy. *Hepatitis B virus* - The complete infectious virion of HBV, known as the **Dane particle**, is a double-shelled spherical particle, which does not have the same internal structure as the virions in the image. - Serum from infected individuals also contains non-infectious spherical and filamentous particles of **HBsAg** which lack a nucleocapsid. *Human papillomavirus* - HPV is a **non-enveloped** DNA virus, whereas the virus in the micrograph is clearly surrounded by a lipid envelope. - It has a simple, small **icosahedral capsid** structure, lacking the complex, multi-layered appearance of a herpesvirus.

Q: Acute hemorrhagic conjunctivitis is caused by which of the following combinations?

Coxsackie A and Enterovirus 70. ### **Explanation: Acute Hemorrhagic Conjunctivitis (AHC)** **Acute Hemorrhagic Conjunctivitis (AHC)** is a highly contagious, self-limiting viral infection characterized by rapid onset, lid edema, and pathognomonic **subconjunctival hemorrhages**. #### **1. Why Option A is Correct** The primary etiological agents for AHC are **Enterovirus 70 (EV-70)** and **Coxsackievirus A24 (CA24)** variant. These are small RNA viruses belonging to the *Picornaviridae* family. * **Enterovirus 70** was the first identified cause during the 1969 pandemic. * **Coxsackie A24** is responsible for several subsequent large-scale outbreaks worldwide. #### **2. Why Other Options are Incorrect** * **Options B, C, and D:** These include **Coxsackie B**. While Coxsackievirus B is a common cause of myocarditis, pleurodynia (Bornholm disease), and meningitis, it is **not** a recognized cause of acute hemorrhagic conjunctivitis. The ocular tropism is specific to the **A24 variant** of Coxsackie A. --- ### **High-Yield Clinical Pearls for NEET-PG / INI-CET** * **Incubation Period:** Extremely short, typically **12 to 48 hours**. * **Clinical Hallmark:** Multiple **petechial hemorrhages** on the bulbar conjunctiva that may coalesce to form a large subconjunctival hemorrhage. * **Neurological Association:** A rare but serious complication of **Enterovirus 70** is a **polio-like paralysis** (radiculomyelitis), which can occur several weeks after the conjunctivitis resolves. * **Differential Diagnosis:** * **Epidemic Keratoconjunctivitis (EKC):** Caused by **Adenovirus (Serotypes 8, 19, 37)**. It presents with prominent pseudomembranes and corneal involvement (subepithelial infiltrates) but less frequent hemorrhage compared to AHC. * **Management:** Supportive treatment only (cold compresses, lubricants); antibiotics are used only to prevent secondary bacterial infection.

Q: A young adult presents with facial pain and painful vesicular lesions in the mouth. Tzanck smear reveals multinucleated giant cells with intranuclear inclusions. What is the most likely causative organism?

Herpes simplex virus. ***Herpes simplex virus*** - The presentation of **painful vesicular lesions** in the mouth and **facial pain** strongly suggests primary (e.g., gingivostomatitis) or reactivated herpes infection. - The **Tzanck smear** showing **multinucleated giant cells** with **intranuclear inclusions** is characteristic of the Herpesviridae family, confirming the clinical suspicion of HSV. *Adenovirus* - Adenovirus typically causes **pharyngoconjunctival fever**, acute respiratory disease, or viral conjunctivitis, not localized vesicular lesions in the mouth. - It does not produce the hallmark cytopathic effect of **multinucleated giant cells** on Tzanck smear. *Cytomegalovirus* - CMV usually presents as a mild **mononucleosis-like syndrome** in healthy adults or causes severe systemic disease in the immunocompromised. - CMV histology is defined by large intranuclear **"owl's eye" inclusions**, a finding different from the multinucleated giant cells seen on Tzanck smear. *Epstein-Barr virus* - EBV causes **Infectious Mononucleosis**, characterized by fever, lymphadenopathy, and pharyngitis, not primarily painful vesicular eruptions. - Although part of the herpes family, EBV typically causes unique lymphoid pathology and **Hairy Leukoplakia**, not the cytopathic changes seen on Tzanck smear.

Q: The following disease presentation is caused by:

Human parvovirus B19. ***Human parvovirus B19*** - The image shows a classic "slapped cheek" rash, which is a hallmark clinical presentation of **fifth disease**, caused by **Human parvovirus B19**. - This rash typically spares the circumoral area and develops after a prodromal phase of mild fever and malaise. *Scarlet fever* - Scarlet fever is characterized by a "sandpaper" rash, which feels rough, and often presents with **circumoral pallor**, but does not typically present as a "slapped cheek" appearance. - Patients often exhibit a **strawberry tongue** and high fever, not typically associated with the image provided. *Arthus phenomenon* - The Arthus phenomenon is a localized **type III hypersensitivity reaction** characterized by pain, swelling, and redness at the site of antigen injection, not a diffuse facial rash like the one seen. - This reaction is an immune complex-mediated process and is not an infectious disease causing a generalized rash. *Epstein-Barr virus* - Epstein-Barr virus (EBV) primarily causes **infectious mononucleosis**, which can produce a maculopapular rash, especially if the patient is treated with amoxicillin. - However, EBV rash does not typically manifest as the distinctive "slapped cheek" appearance seen in the image.

Q: A 25-year-old abattoir worker presents with myoclonus and amnesia for recent and remote events for last 1 year. MRI head was performed. All statements are correct about the organisms leading to this disease except:

Sensitive to ethylene dioxide. ***Sensitive to ethylene dioxide*** - Prions, the causative agents of Creutzfeldt-Jakob Disease (CJD), are **resistant to conventional sterilization methods**, including ethylene oxide, radiation, and disinfectants like formaldehyde. This statement is incorrect. - They are primarily inactivated by methods that denature proteins, such as **autoclaving at high temperatures and pressures** or strong sodium hydroxide solutions. *Absence of nucleic acid* - **Prions are infectious proteinaceous particles** that lack nucleic acid (DNA or RNA), which distinguishes them from viruses, bacteria, and other conventional pathogens. - They propagate by inducing conformational changes in normal host proteins. *CSF examination of patient shows presence of protein 14.3.3* - The presence of **14-3-3 protein** in cerebrospinal fluid (CSF) is a significant and widely used diagnostic marker for **Creutzfeldt-Jakob Disease (CJD)**. - Elevated levels of this protein indicate neuronal damage and are often found in patients with rapidly progressive dementia caused by prions. *MRI shows cortical ribboning* - **Cortical ribboning**, characterized by hyperintense signal changes in the cerebral cortex on diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) sequences, is a **highly characteristic finding in MRI scans of patients with CJD**. - This MRI finding, along with involvement of the basal ganglia and thalamus, supports the diagnosis of CJD.

Q: The following electron microscope image shows presence of:

Ebola virus. ***Ebola virus*** - The electron micrograph clearly shows characteristic **filamentous, long, and pleomorphic viral particles**, some displaying coiled or branched structures, which are hallmarks of the **Filoviridae family**, to which Ebola belongs. - The presence of distinct, elongated forms, often appearing as "shepherd's crook" shapes or U-shaped structures (as indicated by the arrows), is highly indicative of the **Ebola virus morphology**. *Swine flu virus* - Swine flu, caused by influenza viruses, typically presents as **spherical or pleomorphic virions**, but not in the distinct elongated filamentous forms seen in the image. - Influenza viruses have a segmented RNA genome enclosed within a spherical capsid and an outer envelope, giving them a more rounded appearance. *Rabies virus* - Rabies virus has a classical **bullet-shaped morphology**, which is distinctly different from the long, filamentous structures observed in the image. - Its unique shape is a key identifying feature in electron microscopy. *Polio virus* - Poliovirus is a non-enveloped RNA virus with an **icosahedral (spherical) capsid structure**, much smaller and more geometrically regular than the filamentous particles shown. - It does not exhibit the elongated, flexible morphology characteristic of filoviruses.

Question 1

Receptor used for the entry of HIV virus into the host cell is?

Accepted Answer

CCR5

Answer

CD8

Answer

CD6

Answer

CCR7

Question 2

A child was brought with c/o multiple lesions. O/E multiple vesicular lesions are seen on the palms, soles, and oral mucosa. Which of the following is the most likely etiological agent causing the disease?

Accepted Answer

Coxsackie virus

Answer

Varicella-zoster virus

Answer

Measles virus

Answer

Human-herpesvirus 6

Question 3

A patient is positive for HBsAg and anti-HBc IgM. What is the most likely diagnosis?

Accepted Answer

Acute hepatitis

Answer

Recovery phase

Answer

Vaccination

Answer

Chronic hepatitis

Question 4

Which of the following hepatitis viruses is likely to get transmitted via fecal-oral route?

Accepted Answer

Hepatitis A

Answer

Hepatitis B

Answer

Hepatitis C

Answer

Hepatitis D

Question 5

The image shown here is used for the diagnosis of

Accepted Answer

Herpes simplex virus

Answer

Human immunodeficiency virus

Answer

Hepatitis B virus

Answer

Human papillomavirus

Question 6

Acute hemorrhagic conjunctivitis is caused by which of the following combinations?

Accepted Answer

Coxsackie A and Enterovirus 70

Answer

Coxsackie B and Enterovirus 70

Answer

Coxsackie A, Coxsackie B and Enterovirus 70

Answer

Coxsackie A and Coxsackie B

Question 7

A young adult presents with facial pain and painful vesicular lesions in the mouth. Tzanck smear reveals multinucleated giant cells with intranuclear inclusions. What is the most likely causative organism?

Accepted Answer

Herpes simplex virus

Answer

Adenovirus

Answer

Cytomegalovirus

Answer

Epstein-Barr virus

Question 8

The following disease presentation is caused by:

Accepted Answer

Human parvovirus B19

Answer

Scarlet fever

Answer

Arthus phenomenon

Answer

Epstein-Barr virus

Question 9

A 25-year-old abattoir worker presents with myoclonus and amnesia for recent and remote events for last 1 year. MRI head was performed. All statements are correct about the organisms leading to this disease except:

Accepted Answer

Sensitive to ethylene dioxide

Answer

Absence of nucleic acid

Answer

CSF examination of patient shows presence of protein 14.3.3

Answer

MRI shows cortical ribboning

Question 10

The following electron microscope image shows presence of:

Accepted Answer

Ebola virus

Answer

Swine flu virus

Answer

Rabies virus

Answer

Polio virus

Virology — MCQs

Virology — MCQs

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