Virology Practice Questions

Q: What is the most common cause of acute aseptic meningitis in children?

Enterovirus. **Explanation:** **Enteroviruses** (specifically Coxsackievirus A and B, and Echoviruses) are the most common cause of acute aseptic meningitis in children, accounting for **>80-90% of cases** where a pathogen is identified. They typically follow a seasonal pattern, peaking in late summer and early autumn. The virus enters via the fecal-oral or respiratory route, replicates in the lymphoid tissue of the GI tract, and spreads hematogenously to the central nervous system. **Analysis of Incorrect Options:** * **Arboviruses (Option A):** While significant causes of meningoencephalitis (e.g., Japanese Encephalitis in specific endemic regions), they are less common overall than Enteroviruses and often present with more severe parenchymal involvement (encephalitis). * **Respiratory Syncytial Virus (Option B):** RSV is a primary cause of lower respiratory tract infections (bronchiolitis and pneumonia) in infants. It rarely involves the CNS. * **Herpes Family (Option D):** HSV-2 is a common cause of aseptic meningitis in adults, and HSV-1 is the leading cause of sporadic fatal encephalitis. While they cause CNS infections in neonates and children, they do not match the high prevalence of Enteroviruses. **High-Yield Clinical Pearls for NEET-PG:** * **CSF Findings in Aseptic Meningitis:** Normal glucose, normal to slightly elevated protein, and lymphocytic pleocytosis (though neutrophils may predominate in the first 24 hours). * **Diagnosis:** PCR of the CSF is the gold standard for Enteroviral meningitis due to its high sensitivity. * **Prognosis:** Generally excellent with supportive care, unlike bacterial meningitis. * **Hand-Foot-Mouth Disease:** Often co-exists or precedes meningitis caused by Coxsackievirus A16 or Enterovirus 71.

Q: Which of the following hepatitis viruses is non-enveloped?

Hepatitis A virus (HAV). **Explanation:** The classification of hepatitis viruses into enveloped or non-enveloped is a high-yield concept in medical microbiology. Hepatitis viruses that are transmitted via the **fecal-oral route** are typically **non-enveloped**, as they must survive the harsh acidic environment of the gastrointestinal tract. Conversely, those transmitted via blood or body fluids are generally **enveloped**. **1. Why Hepatitis A (HAV) is correct:** HAV belongs to the *Picornaviridae* family. It is a small, **non-enveloped**, single-stranded RNA virus. Its lack of an envelope makes it highly resistant to degradation by bile and gastric acid, facilitating its transmission through contaminated food and water. **Hepatitis E virus (HEV)** is the only other major hepatitis virus that is also non-enveloped. **2. Why the other options are incorrect:** * **Hepatitis B (HBV):** A member of the *Hepadnaviridae* family. It is a DNA virus that possesses a complex lipid envelope containing the HBsAg (surface antigen). * **Hepatitis C (HCV):** A member of the *Flaviviridae* family. It is an enveloped RNA virus. The envelope makes it fragile and dependent on direct blood-to-blood contact for transmission. * **Hepatitis D (HDV):** Known as a "defective" virus, it requires the HBsAg envelope from HBV to become infectious. Thus, it is an enveloped virus. **Clinical Pearls for NEET-PG:** * **Mnemonic:** "The **Vowels** (A and E) go through the **Bowel** (Fecal-oral) and have **No** (Non-enveloped) shell." * **HAV** is the most common cause of acute viral hepatitis in children worldwide. * **HEV** is associated with high mortality (up to 20%) in pregnant women, particularly in the third trimester. * All hepatitis viruses are RNA viruses except **HBV**, which is a **DNA virus**.

Q: Human metapneumovirus is structurally similar to which of the following viruses?

Respiratory syncytial virus. ### Explanation **Correct Answer: B. Respiratory syncytial virus (RSV)** **Why it is correct:** Human metapneumovirus (hMPV) and Respiratory syncytial virus (RSV) both belong to the family **Paramyxoviridae**. Specifically, hMPV is a member of the genus *Metapneumovirus*, while RSV belongs to the genus *Orthopneumovirus* (formerly both were in the subfamily *Pneumovirinae*). Structurally, both are pleomorphic, enveloped viruses containing a **non-segmented, negative-sense, single-stranded RNA** genome. They share similar clinical presentations, primarily causing bronchiolitis and pneumonia in infants and the elderly. **Why the other options are incorrect:** * **A. Influenza virus:** Belongs to the **Orthomyxoviridae** family. Its primary structural difference is a **segmented genome** (8 segments), which allows for antigenic shift. * **C. Measles virus:** While it is in the Paramyxoviridae family (genus *Morbillivirus*), it is structurally and clinically distinct from the pneumoviruses. Measles is characterized by systemic infection, Koplik spots, and a maculopapular rash, rather than being restricted primarily to the respiratory epithelium. * **D. Rubella virus:** Belongs to the **Matonaviridae** family (formerly Togaviridae). It is a positive-sense, single-stranded RNA virus and is much smaller than the paramyxoviruses. **High-Yield Clinical Pearls for NEET-PG:** * **hMPV Discovery:** It was first identified in 2001; it is the second most common cause of lower respiratory tract infections in children after RSV. * **Surface Proteins:** Unlike other Paramyxoviruses, hMPV and RSV **lack Hemagglutinin (H) and Neuraminidase (N)** activities on their attachment proteins. * **Diagnosis:** RT-PCR is the gold standard for hMPV as it is difficult to isolate in standard cell cultures. * **Seasonality:** Similar to RSV, hMPV peaks during late winter and spring.

Q: What is the most important marker in diagnosing acute Hepatitis B?

IgM Anti-HBc. **Explanation:** The diagnosis of acute Hepatitis B relies on identifying markers that appear during the initial phase of infection. **IgM Anti-HBc** is the most important marker because it is the first antibody to appear and is specifically indicative of a **recent/acute infection** (typically within the last 6 months). **Why IgM Anti-HBc is the correct answer:** It is the only reliable marker during the **"Window Period"**—the interval when HBsAg has disappeared but Anti-HBs has not yet become detectable. Its presence confirms acute replication even when other surface markers are negative. **Analysis of incorrect options:** * **IgG Anti-HBc:** This indicates a past infection or chronic state. It persists for life and does not differentiate between an ongoing chronic infection and a recovered state. * **Anti-HBs:** This antibody signifies **immunity**, either through recovery from a natural infection or via vaccination. It appears only after the acute phase has resolved. * **HBsAg:** While it is the first marker to appear in the blood (indicating the presence of the virus), it cannot distinguish between an **acute** infection and a **chronic carrier** state. **High-Yield Clinical Pearls for NEET-PG:** * **First marker to appear:** HBsAg. * **First antibody to appear:** IgM Anti-HBc. * **Marker of Infectivity:** HBeAg (indicates high viral replication). * **Marker of Recovery/Immunity:** Anti-HBs. * **Vaccination Profile:** Only Anti-HBs is positive; all other markers (including Anti-HBc) are negative. * **Window Period Marker:** IgM Anti-HBc is the sole diagnostic tool.

Q: Mad Cow disease (Spongiform disease) occurs due to which of the following?

Prions (specifically, abnormal prion proteins, not viruses). **Explanation:** **Mad Cow Disease**, medically known as **Bovine Spongiform Encephalopathy (BSE)**, is caused by **Prions**. Prions are unique infectious agents because they lack nucleic acids (DNA or RNA). They are misfolded proteins ($PrP^{Sc}$) that induce normal cellular prion proteins ($PrP^C$) in the host’s brain to also misfold into the pathological isoform. This leads to neuronal loss and a characteristic "spongiform" (sponge-like) appearance of the brain tissue. **Analysis of Options:** * **Option A (Correct):** Prions are the established causative agents of Transmissible Spongiform Encephalopathies (TSEs) like BSE in cattle and Creutzfeldt-Jakob Disease (CJD) in humans. * **Option B (Arena Virus):** These are RNA viruses (e.g., Lassa fever, LCMV) that typically cause hemorrhagic fevers or meningitis, not spongiform degeneration. * **Option C (Kuru Virus):** This is a **misnomer**. While Kuru is a spongiform disease, it is caused by **prions** (transmitted via ritualistic cannibalism), not a virus. * **Option D (Parvo Virus):** B19 virus is a DNA virus known for causing Erythema Infectiosum (Fifth disease), aplastic crisis, and hydrops fetalis. **High-Yield Clinical Pearls for NEET-PG:** * **Resistance:** Prions are highly resistant to standard sterilization methods (autoclaving, UV, formalin). Recommended decontamination involves **1N NaOH** or **Sodium Hypochlorite** for 1 hour. * **Human Variant:** Consumption of BSE-infected beef is linked to **variant CJD (vCJD)** in humans. * **Diagnosis:** Characterized by the absence of an inflammatory response and the presence of **14-3-3 protein** in the CSF. * **Amyloid Plaques:** Histology shows extracellular accumulation of prion protein aggregates.

Q: Epstein-Barr virus (EBV) is associated with which of the following conditions, EXCEPT?

Verrucous lymphoma. ### **Explanation** The correct answer is **C. Verrucous lymphoma**. **1. Why Verrucous Lymphoma is the correct answer:** There is no clinical entity known as "Verrucous lymphoma." The term "Verrucous" typically refers to **Verrucous Carcinoma** (a low-grade variant of squamous cell carcinoma), which is primarily associated with **Human Papillomavirus (HPV)** types 6 and 11, not EBV. Therefore, it is the "except" option in this list. **2. Analysis of Incorrect Options (EBV-associated conditions):** * **Nasopharyngeal Carcinoma (Option A):** EBV has a strong causal link with the undifferentiated type (Type III) of nasopharyngeal carcinoma, particularly prevalent in Southern China and Southeast Asia. * **Burkitt’s Lymphoma (Option B):** EBV is associated with the **Endemic (African)** form of Burkitt’s lymphoma, characterized by the $t(8;14)$ translocation involving the *c-myc* oncogene. * **Hodgkin’s Lymphoma (Option D):** EBV is found in approximately 40–50% of Hodgkin’s cases, most commonly the **Mixed Cellularity** subtype. **3. NEET-PG High-Yield Clinical Pearls:** * **Virus Family:** EBV is Human Herpesvirus 4 (HHV-4), a gamma-herpesvirus. * **Cell Tropism:** It infects B-cells via the **CD21 receptor** (also known as CR2). * **Diagnosis:** Look for **Atypical Lymphocytes (Downey cells)** on peripheral smear and a positive **Monospot test** (Heterophile antibodies). * **Other EBV Associations:** * Infectious Mononucleosis (Glandular fever). * Oral Hairy Leukoplakia (seen in HIV/AIDS). * Post-transplant lymphoproliferative disorder (PTLD). * Gastric Carcinoma (subset of cases).

Q: A 3-month-old child was admitted with pneumonia. The microscopy shows the following image. Choose the correct organism.

Influenza. ***Influenza*** - The image displays a virus with two key surface glycoproteins: **Hemagglutinin (HA)** and **Neuraminidase (NA)**. These proteins are the defining structural features of the Influenza virus and are crucial for its entry into and exit from host cells. - Influenza virus is a well-known cause of respiratory illnesses, including severe **pneumonia**, particularly in high-risk groups such as infants, the elderly, and immunocompromised individuals. *Rotavirus* - Rotavirus is the leading cause of severe **gastroenteritis** (diarrhea and vomiting) in infants and young children; it is not a primary cause of pneumonia. - It is a **non-enveloped** virus with a distinct wheel-like appearance (hence the name "rota"), which is structurally different from the enveloped virus shown in the diagram. *Hepatitis virus* - Hepatitis viruses (A, B, C, etc.) are hepatotropic, meaning they primarily infect and cause inflammation of the **liver (hepatitis)**, and are not associated with respiratory infections like pneumonia. - Their viral structures and surface antigens are different; for example, Hepatitis B virus has **HBsAg** on its surface, not HA and NA. *Respiratory syncytial virus* - While RSV is a very common cause of **pneumonia** and **bronchiolitis** in infants, its viral structure differs from the one depicted. - RSV belongs to the *Paramyxoviridae* family and has **Fusion (F)** and **Attachment (G)** proteins on its surface, not Hemagglutinin and Neuraminidase.

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].

Question 1

What is the most common cause of acute aseptic meningitis in children?

Accepted Answer

Enterovirus

Answer

Arbovirus

Answer

Respiratory syncytial virus

Answer

Herpes family

Question 2

Which of the following hepatitis viruses is non-enveloped?

Accepted Answer

Hepatitis A virus (HAV)

Answer

Hepatitis B virus (HBV)

Answer

Hepatitis C virus (HCV)

Answer

Hepatitis D virus (HDV)

Question 3

Human metapneumovirus is structurally similar to which of the following viruses?

Accepted Answer

Respiratory syncytial virus

Answer

Influenza virus

Answer

Measles virus

Answer

Rubella virus

Question 4

What is the most important marker in diagnosing acute Hepatitis B?

Accepted Answer

IgM Anti-HBc

Answer

IgG Anti-HBc

Answer

Anti HBs

Answer

HBsAg

Question 5

Mad Cow disease (Spongiform disease) occurs due to which of the following?

Accepted Answer

Prions (specifically, abnormal prion proteins, not viruses)

Answer

Arena Virus

Answer

Kuru Virus

Answer

Parvo Virus

Question 6

Epstein-Barr virus (EBV) is associated with which of the following conditions, EXCEPT?

Accepted Answer

Verrucous lymphoma

Answer

Nasopharyngeal carcinoma

Answer

Burkitt's lymphoma

Answer

Hodgkin's lymphoma

Question 7

A 3-month-old child was admitted with pneumonia. The microscopy shows the following image. Choose the correct organism.

Accepted Answer

Influenza

Answer

Rotavirus

Answer

Hepatitis virus

Answer

Respiratory syncytial virus

Question 8

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

Accepted Answer

CCR5

Answer

CD8

Answer

CD6

Answer

CCR7

Question 9

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 10

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

Virology — MCQs

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