Virology Practice Questions

Q: Which of the following is/are arboviral diseases?

Hand-foot-mouth disease. **Explanation:** The term **Arbovirus** (Arthropod-borne virus) refers to a functional group of viruses that are transmitted to humans through the bite of infected arthropods, primarily mosquitoes and ticks. **Why Hand-foot-mouth disease (HFMD) is the correct answer (as the non-arboviral disease):** HFMD is caused by viruses belonging to the **Picornaviridae** family, most commonly **Coxsackievirus A16** and **Enterovirus 71**. Unlike arboviruses, these are transmitted via the **fecal-oral route**, respiratory droplets, or direct contact with lesion fluid. They do not require an arthropod vector for transmission. **Analysis of Incorrect Options (Arboviral Diseases):** * **Japanese Encephalitis (JE):** An arboviral disease caused by a Flavivirus. It is transmitted by the **Culex tritaeniorhynchus** mosquito. * **Dengue:** Caused by the Dengue virus (Flavivirus) and transmitted primarily by the **Aedes aegypti** mosquito. * **Kyasanur Forest Disease (KFD):** A viral hemorrhagic fever caused by a Flavivirus. It is a tick-borne disease transmitted by **Haemaphysalis spinigera**. **High-Yield Clinical Pearls for NEET-PG:** * **Arbovirus Families:** Most belong to *Flaviviridae* (Dengue, JE, KFD, West Nile, Zika), *Togaviridae* (Chikungunya), or *Bunyaviridae* (Crimean-Congo Hemorrhagic Fever). * **Vector Identification:** Always remember the specific vectors: *Aedes* (Dengue/Zika/Chikungunya), *Culex* (JE), and *Ticks* (KFD/CCHF). * **HFMD Presentation:** Characterized by a vesicular rash on the palms, soles, and oral ulcers (herpangina). It is a common pediatric infection and is **not** seasonal in the same way vector-borne diseases are.

Q: Which of the following is NOT included in the picornavirus group?

Hepatitis E virus (HEV). **Explanation:** The **Picornaviridae** family consists of small (pico), non-enveloped, positive-sense single-stranded RNA viruses. **Why Hepatitis E Virus (HEV) is the correct answer:** Hepatitis E virus was previously classified under Picornaviridae due to its similar morphology. However, it is now classified in its own family, **Hepeviridae** (Genus: *Orthohepevirus*). Unlike picornaviruses, HEV has a unique genomic organization and is the only major hepatitis virus that is "quasi-enveloped" in the blood but non-enveloped in feces. **Analysis of Incorrect Options:** * **Poliovirus:** A classic member of the *Enterovirus* genus within the Picornaviridae family. It is the causative agent of paralytic poliomyelitis. * **Foot and Mouth Disease Virus (FMDV):** Belonging to the *Aphthovirus* genus, it is a highly infectious picornavirus affecting cloven-hoofed animals; it is historically significant as the first animal virus discovered. * **Encephalomyocarditis Virus (EMCV):** A member of the *Cardiovirus* genus within Picornaviridae, known for causing encephalitis and myocarditis in a wide range of mammalian hosts. **High-Yield Clinical Pearls for NEET-PG:** * **Picornavirus Mnemonic (PERCH):** **P**olio, **E**cho, **R**hino, **C**oxsackie, and **H**epatitis A. * **Hepatitis E Key Fact:** It is the most common cause of acute viral hepatitis worldwide and carries a high mortality rate (up to 20%) in **pregnant women** due to fulminant hepatic failure. * **Rhinovirus:** The only picornavirus that is **acid-labile** (destroyed by stomach acid), which is why it causes respiratory infections rather than GI disease.

Q: Antigenic drift and antigenic shift are characteristic features of which virus?

Influenza A virus. **Explanation:** The correct answer is **Influenza A virus**. This virus belongs to the Orthomyxoviridae family and possesses a **segmented RNA genome** (8 segments), which is the structural basis for its unique genetic variations: 1. **Antigenic Drift:** These are **point mutations** in the genes coding for Hemagglutinin (HA) and Neuraminidase (NA). This occurs in both Influenza A and B, leading to seasonal epidemics and necessitating the annual update of the flu vaccine. 2. **Antigenic Shift:** This is a major change involving **genetic reassortment** between different strains (e.g., human and avian) infecting the same cell. This only occurs in **Influenza A** because it infects multiple species (birds, pigs, humans). This results in a new subtype, leading to **pandemics**. **Analysis of Incorrect Options:** * **Swine flu virus (H1N1):** While H1N1 undergoes these processes, it is a specific *subtype* of Influenza A. In medical exams, the broader category "Influenza A" is the standard answer as it encompasses all subtypes capable of shifting. * **Rotavirus:** Although it has a segmented genome (11 segments) and can undergo reassortment, the specific terms "antigenic drift/shift" are classically reserved for Influenza nomenclature in clinical virology. * **Herpes virus:** This is a DNA virus. DNA viruses have proofreading mechanisms and do not undergo rapid antigenic variation or reassortment like segmented RNA viruses. **High-Yield Clinical Pearls for NEET-PG:** * **Pandemics** are caused by **Shift**; **Epidemics** are caused by **Drift**. * Influenza **B** only undergoes **Drift** (no animal reservoir). * The site of Influenza virus replication is unique: it is an RNA virus that replicates in the **nucleus**. * **Amantadine** inhibits the M2 ion channel; **Oseltamivir** inhibits Neuraminidase.

Q: Which statement is incorrect regarding the hepatitis B virus?

It is transmitted via the fecal-oral route.. ### Explanation **1. Why Option B is the correct (incorrect statement):** Hepatitis B Virus (HBV) is **not** transmitted via the fecal-oral route. It is primarily transmitted through parenteral routes (blood transfusion, contaminated needles), sexual contact, and vertical transmission (mother to child). Fecal-oral transmission is characteristic of **Hepatitis A and E** ("The vowels hit the bowels"). **2. Analysis of other options:** * **Option A (DNA Virus):** HBV is a member of the *Hepadnaviridae* family. It is the only DNA virus among the major hepatitis viruses (A, B, C, D, and E are all RNA viruses). * **Option C (Perinatal transmission):** This is a major route of transmission, especially in endemic areas. If a mother is HBeAg positive, the risk of transmission to the neonate is as high as 90%. * **Option D (Reverse Transcriptase):** HBV has a unique replication cycle. Its genome is partially double-stranded DNA (dsDNA). It uses an enzyme called **RNA-dependent DNA polymerase (Reverse Transcriptase)** to transcribe its genomic DNA from an intermediate RNA template (pre-genome). **3. High-Yield Clinical Pearls for NEET-PG:** * **Structure:** HBV is a 42 nm particle known as the **Dane particle**. * **Serology Marker of Infectivity:** The presence of **HBeAg** indicates high viral replication and high infectivity. * **Window Period:** The interval when HBsAg has disappeared but Anti-HBs has not yet appeared. During this time, **Anti-HBc IgM** is the only diagnostic marker. * **Ground Glass Hepatocytes:** The characteristic histopathological finding in chronic Hepatitis B due to the accumulation of HBsAg in the endoplasmic reticulum.

Q: Which of the following statements about Dengue fever is incorrect?

It has an incubation period of 2-3 weeks.. ### Explanation **1. Why Option B is the Correct Answer (Incorrect Statement):** The incubation period of Dengue fever is typically **3 to 14 days** (average 4–7 days), not 2–3 weeks. In clinical virology, an incubation period exceeding 14 days is rare for most arboviral infections. Identifying the correct timeline is crucial for epidemiological tracking and diagnosing returning travelers. **2. Analysis of Other Options:** * **Option A:** Dengue is primarily transmitted by the **Aedes aegypti** mosquito (the principal vector) and occasionally by *Aedes albopictus*. These are "day-biters" that breed in stagnant clean water. * **Option C:** The Dengue virus (DENV) belongs to the genus **Flavivirus** and family *Flaviviridae*. It is a single-stranded, positive-sense RNA virus with four distinct serotypes (DEN-1 to DEN-4). * **Option D:** Dengue is classically known as **"Break-bone fever"** due to the characteristic severe myalgia, arthralgia, and retro-orbital pain associated with the febrile phase. **3. NEET-PG High-Yield Pearls:** * **Diagnosis:** **NS1 Antigen** is the marker of choice for the first 1–5 days. **IgM ELISA** is used after day 5. * **Pathogenesis:** Severe forms like Dengue Hemorrhagic Fever (DHF) occur due to **Antibody-Dependent Enhancement (ADE)**, usually during a secondary infection with a different serotype. * **Tourniquet Test:** A positive test (≥10 petechiae per square inch) indicates capillary fragility, a hallmark of DHF. * **Hematology:** Characterized by **leukopenia** and **thrombocytopenia**. A rising hematocrit (>20% increase) is a critical sign of plasma leakage.

Q: Which virus is noted for such a high incidence of antigenic drift that more than one antigenic variant can be isolated from infected individuals?

HIV. ### Explanation The correct answer is **HIV (Human Immunodeficiency Virus)**. **Why HIV is correct:** The hallmark of HIV is its extreme genetic diversity, driven by the error-prone nature of the **Reverse Transcriptase** enzyme, which lacks 3' to 5' exonuclease (proofreading) activity. This leads to a high rate of point mutations during replication. Consequently, HIV undergoes such rapid **antigenic drift** that it exists within a single patient as a collection of closely related but distinct genetic variants known as **quasispecies**. This allows the virus to constantly evade the host’s immune response and complicates vaccine development. **Why other options are incorrect:** * **Influenza Virus:** While famous for antigenic drift (causing seasonal epidemics) and shift (causing pandemics), the variants typically emerge at a population level over time. It does not usually produce multiple distinct antigenic variants within a single host simultaneously to the extent HIV does. * **Adenovirus & Herpesvirus:** These are **DNA viruses**. DNA polymerases generally have proofreading mechanisms, making these viruses genetically stable compared to RNA viruses. They do not exhibit significant antigenic drift. **High-Yield Clinical Pearls for NEET-PG:** * **Quasispecies:** This term specifically refers to the diverse pool of HIV variants within one individual. * **Reverse Transcriptase:** The highest mutation rate among all known biological entities ($10^{-4}$ to $10^{-5}$ mutations per base pair per cycle). * **Influenza Antigenic Shift:** Due to the **segmented genome** (8 segments), allowing for genetic reassortment. * **HIV Tropism:** Determined by the **gp120** protein binding to CD4 receptors and co-receptors (CCR5 or CXCR4).

Q: Herpangina is commonly caused by which virus?

Coxsackie virus B. **Explanation:** **Herpangina** is an acute febrile illness characterized by small vesicular and ulcerative lesions on the posterior oropharynx (tonsillar pillars, soft palate, and uvula). It is primarily caused by **Coxsackievirus Group A** (specifically types A1–A10, A16, and A22). *Note: There appears to be a discrepancy in the provided key. In standard medical microbiology (Jawetz, Harrison, Bailey & Scott), Herpangina is classically associated with **Coxsackievirus Group A**, while Group B is more commonly associated with Pleurodynia and Myocarditis.* **Analysis of Options:** * **Coxsackievirus A (Correct Pathogen):** This is the most common cause of Herpangina and Hand-Foot-Mouth Disease (HFMD). It typically affects children and presents with sudden fever and sore throat. * **Coxsackievirus B:** While it can cause respiratory infections, it is the classic cause of **Bornholm disease (Pleurodynia)**, Myocarditis, and Pericarditis. * **Echovirus:** These can cause aseptic meningitis and non-specific exanthems but are less frequent causes of classic Herpangina. * **Poliovirus:** Primarily causes asymptomatic infection, abortive poliomyelitis, or paralytic disease by affecting the anterior horn cells of the spinal cord. **High-Yield Clinical Pearls for NEET-PG:** * **Herpangina vs. Herpes Stomatitis:** Herpangina lesions are located in the **posterior** pharynx, whereas Gingivostomatitis (HSV-1) typically involves the **anterior** mouth and gums. * **Hand-Foot-Mouth Disease (HFMD):** Most commonly caused by **Coxsackie A16** and **Enterovirus 71**. * **Pleurodynia (Devil’s Grip):** Characterized by paroxysmal thoracic pain, caused by **Coxsackie B**. * **Myocarditis:** Coxsackie B is the most common viral cause of infectious myocarditis.

Q: Which virus can be easily cultured from CSF?

Mumps virus. **Explanation:** The correct answer is **Mumps virus**. In the context of viral meningitis, the ability to isolate a virus from the cerebrospinal fluid (CSF) depends on the duration and magnitude of the viral load during the clinical phase. **Why Mumps virus is correct:** Mumps virus is highly neurotropic. In patients presenting with mumps meningitis, the virus is shed in high titers into the CSF. It can be successfully cultured from the CSF in approximately **50–70% of cases** during the first week of symptoms. This makes it one of the most "culture-positive" viruses in clinical virology compared to other common causes of aseptic meningitis. **Why the other options are incorrect:** * **Poliovirus:** While Poliovirus causes significant CNS pathology (anterior horn cell destruction), it is **rarely isolated from the CSF**. Diagnosis is typically made via stool culture or throat swabs, as the virus replicates in the oropharynx and intestines. * **Coxsackievirus & Echovirus:** These are Enteroviruses. While they are the most common causes of viral meningitis, their isolation rate from CSF is significantly lower than that of Mumps (typically <30-40%). They are more easily recovered from throat swabs or fecal samples. **NEET-PG High-Yield Pearls:** * **Most common cause of viral meningitis:** Enteroviruses (Coxsackie and Echo). * **Mumps Meningitis:** Occurs in up to 15% of mumps cases; it is usually benign and self-limiting. * **CSF Findings in Viral Meningitis:** Lymphocytic pleocytosis, normal glucose, and slightly elevated protein. * **Gold Standard for Enterovirus:** Though culture is possible, **RT-PCR** is now the diagnostic method of choice for all viral CNS infections due to higher sensitivity and speed.

Q: Which of the following viruses does not cause chronic hepatitis?

Hepatitis E virus (HEV). **Explanation:** The correct answer is **Hepatitis E virus (HEV)**. The underlying medical concept is the mode of transmission and the nature of the viral infection. HEV is primarily transmitted via the **fecal-oral route** and typically causes an acute, self-limiting infection. In immunocompetent individuals, it does not progress to chronicity. * **Hepatitis E (Option D):** While it is generally acute, a high-yield exception for NEET-PG is that HEV can cause chronic hepatitis **only in immunocompromised individuals** (e.g., organ transplant recipients). However, in the general population, it is not a cause of chronic liver disease. * **Hepatitis B (Option A):** HBV is a DNA virus that can lead to chronic infection in about 5-10% of adults and up to 90% of neonates (vertical transmission). * **Hepatitis C (Option B):** HCV is notorious for chronicity, with approximately **75-85%** of infected individuals developing chronic hepatitis, often leading to cirrhosis and hepatocellular carcinoma. * **Hepatitis D (Option C):** HDV is a defective virus that requires HBV (HBsAg) for replication. Both co-infection and super-infection can lead to chronic states, with super-infection carrying a very high risk of rapid progression to chronic liver failure. **High-Yield Clinical Pearls for NEET-PG:** 1. **HEV in Pregnancy:** HEV (Genotype 1 and 2) is associated with high mortality (up to 20%) in pregnant women due to fulminant hepatic failure. 2. **Vowels to the Bowels:** Hepatitis **A** and **E** are transmitted via the fecal-oral route and generally do not cause chronic disease. 3. **Consonants to the Blood:** Hepatitis **B, C, and D** are transmitted parenterally and are the primary causes of chronic hepatitis.

Question 1

Which of the following is/are arboviral diseases?

Accepted Answer

Hand-foot-mouth disease

Answer

Japanese encephalitis

Answer

Dengue

Answer

Kyasanur Forest Disease (KFD)

Question 2

Which of the following is NOT included in the picornavirus group?

Accepted Answer

Hepatitis E virus (HEV)

Answer

Encephalomyocarditis virus

Answer

Foot and mouth disease virus

Answer

Poliovirus

Question 3

Antigenic drift and antigenic shift are characteristic features of which virus?

Accepted Answer

Influenza A virus

Answer

Swine flu virus

Answer

Rotavirus

Answer

Herpes virus

Question 4

Which statement is incorrect regarding the hepatitis B virus?

Accepted Answer

It is transmitted via the fecal-oral route.

Answer

It is a DNA virus.

Answer

It can be transmitted from mother to child (perinatal transmission).

Answer

It contains reverse transcriptase.

Question 5

Which of the following statements about Dengue fever is incorrect?

Accepted Answer

It has an incubation period of 2-3 weeks.

Answer

It is spread by the vector Aedes aegypti.

Answer

It is caused by a Flavivirus.

Answer

It characteristically causes severe myalgia.

Question 6

Which virus is noted for such a high incidence of antigenic drift that more than one antigenic variant can be isolated from infected individuals?

Accepted Answer

HIV

Answer

Adenovirus

Answer

Herpesvirus

Answer

Influenza Virus

Question 7

Which of the following statements best describes subacute sclerosing panencephalitis (SSPE) virus?

Accepted Answer

It is a progressive disease involving both white and gray matter.

Answer

It is a late central nervous system manifestation of mumps.

Answer

It is a common event occurring in 1 of 300,000 cases of mumps.

Answer

Viral DNA can be demonstrated in brain cells.

Question 8

Herpangina is commonly caused by which virus?

Accepted Answer

Coxsackie virus B

Answer

Coxsackie virus A

Answer

Echovirus

Answer

Poliovirus

Question 9

Which virus can be easily cultured from CSF?

Accepted Answer

Mumps virus

Answer

Poliovirus

Answer

Coxsackievirus

Answer

Echovirus

Question 10

Which of the following viruses does not cause chronic hepatitis?

Accepted Answer

Hepatitis E virus (HEV)

Answer

Hepatitis B virus (HBV)

Answer

Hepatitis C virus (HCV)

Answer

Hepatitis D virus (HDV)

Virology — MCQs

Virology — MCQs

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