Virology Practice Questions

Q: A 9-year-old boy presents with a severe sore throat, fever, and dysphagia. Physical examination reveals grayish-white papulovesicular lesions on an erythematous base that have ulcerated. The lesions are located on the soft palate, anterior pillars of the tonsils, and uvula, but not on the gingiva, tongue, or lips. A clinical diagnosis of herpangina is made. Which of the following is the most likely causative organism?

Coxsackievirus A. The clinical presentation of fever, sore throat, and characteristic **grayish-white papulovesicular lesions** localized specifically to the **posterior oropharynx** (soft palate, tonsillar pillars, and uvula) is diagnostic of **Herpangina**. [1] 1. **Why Coxsackievirus A is correct:** Herpangina is most commonly caused by **Coxsackievirus Group A** (specifically types A1–A10, A12, and A22). The hallmark of this infection is the anatomical distribution of the ulcers; they are confined to the posterior structures of the mouth and spare the anterior oral cavity (lips, tongue, and gingiva). [1] 2. **Why other options are incorrect:** * **HSV-1:** Causes **Gingivostomatitis**. Unlike Herpangina, HSV-1 lesions typically involve the **anterior** mouth, including the gingiva (gums), lips (herpes labialis), and the tongue. * **Measles:** Associated with **Koplik spots**, which are bluish-white spots on an erythematous base found on the **buccal mucosa** opposite the lower molars, usually appearing during the prodromal phase. * **Rubella:** May present with **Forchheimer spots** (petechiae on the soft palate), but these are not ulcerative vesicles and are accompanied by prominent post-auricular lymphadenopathy. **NEET-PG High-Yield Pearls:** * **Herpangina vs. Hand-Foot-Mouth Disease (HFMD):** Both are caused by Coxsackievirus A (A16 is common for HFMD). HFMD includes the posterior pharyngeal lesions plus vesicles on the palms, soles, and buttocks. [1] * **Seasonality:** These infections typically peak in **summer and early autumn**. [1] * **Management:** Treatment is purely supportive (hydration and analgesics) as the condition is self-limiting. [1]

Q: The recent avian flu outbreak is caused by which of the following strains?

H5N1. **Explanation:** **Correct Option: B (H5N1)** Influenza A viruses are classified based on two surface glycoproteins: **Hemagglutinin (H)** and **Neuraminidase (N)**. **H5N1** is a highly pathogenic avian influenza (HPAI) virus. While it primarily circulates among wild birds and poultry, recent global outbreaks have seen significant transmission to mammals and occasional "spillover" to humans. It is currently the predominant strain responsible for the ongoing global avian flu crisis. **Analysis of Incorrect Options:** * **A. H1N1:** This strain was responsible for the **1918 Spanish Flu** and the **2009 Swine Flu** pandemic. It is now considered a seasonal human influenza virus. * **C. H7N9:** This is another avian strain that caused a major outbreak in China in 2013. While it has high mortality in humans, it is not the strain driving the current global outbreak. * **D. H7N7:** This strain has caused sporadic outbreaks in poultry and rare, usually mild, infections in humans (conjunctivitis), but it is not the primary strain of current concern. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Shift:** Major genetic changes (reassortment) leading to pandemics (e.g., H1N1 2009). * **Antigenic Drift:** Minor point mutations causing seasonal epidemics; this is why the flu vaccine is updated annually. * **Drug of Choice:** Neuraminidase inhibitors like **Oseltamivir** (Tamiflu) are used for both treatment and prophylaxis. * **Gold Standard Diagnosis:** Real-time RT-PCR is the preferred method for detecting avian influenza in clinical specimens.

Q: Which of the following statements is true regarding human metapneumovirus?

It is a segmented negative-sense single-stranded RNA virus.. ### Explanation **Human Metapneumovirus (hMPV)** is a significant respiratory pathogen belonging to the **Paramyxoviridae** family (subfamily Pneumovirinae). **1. Why Option A is Correct:** Human metapneumovirus is characterized by a **negative-sense, single-stranded RNA (ssRNA)** genome. While most Paramyxoviruses have non-segmented genomes, hMPV is classified within the same family as RSV. It utilizes an RNA-dependent RNA polymerase to replicate within the cytoplasm of host respiratory epithelial cells. **2. Why the Other Options are Incorrect:** * **Option B:** While hMPV is a common cause of upper and lower respiratory tract infections (LRTIs), its incidence is generally estimated to be between **7% and 15%** of all pediatric respiratory hospitalizations, often ranking second only to RSV. * **Option C:** hMPV is a respiratory virus. It spreads primarily through **respiratory droplets**, direct contact with contaminated secretions, or fomites. It is not a blood-borne or sexually transmitted infection. * **Option D:** **NS1 and NS2** (Non-Structural) proteins are characteristic features of **Respiratory Syncytial Virus (RSV)**. Human metapneumovirus is distinguished from RSV by the **absence** of these specific non-structural genes. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** It mimics RSV, causing bronchiolitis and pneumonia, especially in children, the elderly, and the immunocompromised. * **Seasonality:** Peak incidence typically occurs in **late winter and spring** (slightly later than the peak RSV season). * **Diagnosis:** **RT-PCR** is the gold standard for detection, as the virus is difficult to culture. * **Key Distinction:** Unlike RSV, hMPV lacks the NS1 and NS2 genes, which is a common molecular biology question in competitive exams.

Q: The Hella cell line belongs to which category of cell culture?

Continuous cell line. **Explanation:** The **HeLa cell line** is the most famous example of a **Continuous cell line** (also known as immortalized or established cell lines). These are derived from cancer cells or by transforming normal cells with oncogenic viruses or chemicals. 1. **Why "Continuous cell line" is correct:** Continuous cell lines are characterized by their ability to undergo **infinite subcultures** (immortality). HeLa cells were originally derived from a cervical carcinoma biopsy of a patient named Henrietta Lacks in 1951. Because they are malignant in nature, they have lost contact inhibition and can be maintained indefinitely in vitro, making them ideal for large-scale virus vaccine production and research. 2. **Why other options are incorrect:** * **Primary cell culture:** These are normal cells taken directly from an animal/human organ (e.g., Monkey kidney cells). They can only be subcultured once or twice before dying. * **Diploid cell strains:** These are cells that maintain a normal chromosome complement and can be subcultured about 50 times before undergoing senescence (e.g., WI-38, MRC-5). * **Tissue culture:** This is a broad, generic term encompassing all types of cell, organ, and protoplast cultures; it is not a specific category of cell line longevity. **High-Yield Facts for NEET-PG:** * **HeLa Cells:** Derived from Human Cervical Adenocarcinoma. * **Other Continuous Lines:** **HEp-2** (Human Epithelioma of Larynx), **Vero** (Vervet Monkey Kidney), **BHK-21** (Baby Hamster Kidney). * **Diploid Strains:** Used for producing human vaccines (e.g., Rabies, Rubella) because they are non-oncogenic. * **Cytopathic Effect (CPE):** The structural changes in host cells caused by viral invasion, often visualized using these cell lines.

Q: Which of the following microorganisms commonly shows antigenic drift in its pathogenicity?

Influenza virus. **Explanation:** The correct answer is **C. Influenza virus**. **1. Why Influenza Virus is Correct:** Antigenic drift refers to the gradual accumulation of **point mutations** in the genes encoding surface glycoproteins, specifically **Hemagglutinin (HA)** and **Neuraminidase (NA)**. Because the viral RNA polymerase lacks proofreading capability, these minor genetic changes occur frequently. This results in altered viral strains that can partially evade the host’s preexisting immune system, necessitating the annual update of the influenza vaccine. This phenomenon occurs in Influenza types A, B, and C. **2. Why Other Options are Incorrect:** * **A, B, and D (Cholera, Diphtheria, and Plague):** These are bacterial pathogens (*Vibrio cholerae, Corynebacterium diphtheriae,* and *Yersinia pestis*). Unlike RNA viruses, bacteria have more stable genomes with DNA repair mechanisms. While they can undergo genetic variation (e.g., horizontal gene transfer or strain variation), they do not exhibit "antigenic drift," which is a specific virological term describing the mechanism of seasonal epidemic variation in viruses. **3. NEET-PG High-Yield Pearls:** * **Antigenic Drift:** Minor change (point mutations); causes **epidemics**; seen in Influenza A and B. * **Antigenic Shift:** Major change (genetic **reassortment** of segments); causes **pandemics**; seen **only in Influenza A** because it has a broad host range (humans, birds, pigs). * **Segmented Genome:** Influenza is an Orthomyxovirus with 8 RNA segments (Type A and B), which is the structural prerequisite for antigenic shift. * **Vaccine Strain Selection:** The WHO Global Influenza Surveillance and Response System monitors "drift" to decide the composition of the next season's quadrivalent vaccine.

Q: What is the usual causative agent of infection in renal transplant patients?

Cytomegalovirus (CMV). **Explanation:** **Cytomegalovirus (CMV)** is the most common clinically significant viral pathogen in renal transplant recipients, typically manifesting within the first 1 to 6 months post-transplantation. The primary medical concept involves the **reactivation of latent virus** (sequestered in monocytes and macrophages) or transmission via the donor organ during a period of intense therapeutic immunosuppression. CMV is a major cause of morbidity, leading to "CMV syndrome" (fever, malaise, leucopenia) or tissue-invasive diseases like pneumonitis, hepatitis, and colitis. **Analysis of Incorrect Options:** * **HIV (Option B):** While HIV-positive patients can undergo transplants, HIV is not a "usual" causative agent of post-transplant infection; rather, it is a pre-existing condition or a rare transfusion/transplant-acquired risk. * **Herpes Simplex Virus (Option C):** HSV reactivation is common (causing mucocutaneous lesions), but it occurs less frequently and with less systemic severity than CMV in the modern era of prophylaxis. * **Salmonella species (Option D):** While transplant patients are at risk for intracellular bacterial infections, *Salmonella* is far less common than viral opportunistic infections like CMV. **NEET-PG High-Yield Pearls:** * **Timing:** CMV typically appears in the "middle period" (1–6 months) post-transplant. * **Diagnosis:** The gold standard for monitoring is **Quantitative PCR** for CMV DNA. Histopathology shows characteristic **"Owl’s eye" intranuclear inclusions**. * **Treatment:** **Valganciclovir** (prophylaxis/mild disease) and **Ganciclovir** (treatment of choice for active infection). * **Other Viral Risks:** **BK Virus** is another high-yield pathogen specifically linked to **ureteric stenosis and nephropathy** in renal transplants.

Q: A 33-year-old male with AIDS and a history of shingles develops a severe, multifocal encephalitis. Therapy is instituted with acyclovir, but the man dies on the fourth day of his hospital admission. Which of the following viruses is the most likely cause of his encephalitis?

Herpes zoster-varicella. **Explanation:** The correct answer is **Herpes zoster-varicella (VZV)**. This diagnosis is clinically supported by the patient’s history of shingles (reactivation of VZV) and his immunocompromised state (AIDS). In HIV-positive patients, VZV can cause a severe, multifocal, and often fatal encephalitis or vasculopathy. While **Acyclovir** is the treatment of choice, mortality remains high in advanced immunosuppression if therapy is delayed. **Analysis of Options:** * **Cytomegalovirus (CMV):** While CMV is a common cause of encephalitis in AIDS (typically when CD4 <50), it usually presents as a subacute periventricular encephalitis or ventriculitis rather than a multifocal pattern following a history of shingles. * **Herpes simplex type I (HSV-1):** This is the most common cause of sporadic fatal encephalitis in the general population, typically localized to the **temporal lobes**. It does not specifically correlate with a prior history of shingles. * **Herpes simplex type II (HSV-2):** In adults, HSV-2 is more commonly associated with **aseptic meningitis** rather than severe multifocal encephalitis, though it can cause encephalitis in neonates. **Clinical Pearls for NEET-PG:** * **VZV Encephalitis:** Look for the triad of **HIV/Immunosuppression + History of dermatomal rash (shingles) + Neurological deficit.** * **Imaging:** VZV often shows multifocal small and large infarcts (vasculopathy) at the gray-white matter junction. * **HSV-1 Key Fact:** Characterized by hemorrhagic necrosis of the temporal lobes and "Cowdry Type A" intranuclear inclusion bodies. * **Treatment:** High-dose intravenous Acyclovir is the gold standard for both HSV and VZV encephalitis.

Q: Which of the following flaviviruses is closely related to the Russian spring-summer encephalitis virus?

Kyasanur Forest Disease (KFD). **Explanation:** The **Russian spring-summer encephalitis (RSSE)** virus and **Kyasanur Forest Disease (KFD)** virus both belong to the **Tick-borne encephalitis (TBE) complex** within the *Flaviviridae* family. They share significant antigenic similarities and are both transmitted by the bite of infected ticks (specifically *Ixodes* for RSSE and *Haemaphysalis spinigera* for KFD). **Why Kyasanur Forest Disease (KFD) is correct:** KFD is often referred to as "Monkey Fever" and is endemic to the Western Ghats of India. It is antigenically closely related to RSSE. Both viruses cause a biphasic illness characterized by fever and hemorrhagic manifestations or neurological involvement. Because of this close relationship, the RSSE vaccine has historically been used to provide cross-protection against KFD. **Why other options are incorrect:** * **Dengue and Yellow Fever:** While these are also Flaviviruses, they belong to the **Mosquito-borne** group (transmitted by *Aedes aegypti*). They are antigenically distinct from the Tick-borne encephalitis complex. * **Chikungunya:** This is an **Alphavirus** (family *Togaviridae*), not a Flavivirus. It is transmitted by *Aedes* mosquitoes and primarily causes severe arthralgia. **High-Yield Clinical Pearls for NEET-PG:** * **Vector for KFD:** *Haemaphysalis spinigera* (Hard tick). * **Reservoirs for KFD:** Monkeys (Langurs and Bonnet macaques) are the common amplifiers; their death is often a sentinel event for an outbreak. * **TBE Complex Members:** Includes RSSE, KFD, Omsk Hemorrhagic Fever, and Powassan virus. * **Diagnosis:** PCR is the gold standard in the early phase; IgM ELISA is used later.

Q: A patient presented with features of acute hepatitis following a blood transfusion a few weeks ago. Which of the following serological markers indicates the acute phase of hepatitis B infection?

Anti HBc positive, HBsAg positive. ### Explanation **1. Why Option A is Correct:** In the acute phase of Hepatitis B Virus (HBV) infection, the first detectable serum marker is **HBsAg** (Hepatitis B surface Antigen). Shortly after, the body produces antibodies against the core antigen (**Anti-HBc**). Specifically, **IgM Anti-HBc** is the hallmark of acute infection. Since HBsAg indicates the presence of the virus and Anti-HBc (IgM) confirms a recent primary response, the combination of **HBsAg (+) and Anti-HBc (+)** is diagnostic of acute hepatitis B. **2. Analysis of Incorrect Options:** * **Option B (Anti-HBe +, HBsAg +):** This pattern typically indicates a later stage of infection or chronic hepatitis B with low viral replication (seroconversion from HBeAg to Anti-HBe). It does not define the acute phase. * **Option C (Anti-HBs +, HBsAg -):** This indicates **immunity**. If Anti-HBc is also present, it signifies recovery from a natural infection; if only Anti-HBs is present, it signifies successful vaccination. * **Option D (HBeAg -, HBsAg -):** This represents a state where the virus is not actively replicating or has been cleared. It is inconsistent with a patient currently presenting with acute hepatitis symptoms. **3. NEET-PG High-Yield Pearls:** * **Window Period:** The interval when HBsAg has disappeared but Anti-HBs has not yet appeared. During this time, **IgM Anti-HBc** is the *only* diagnostic marker present. * **Infectivity Marker:** **HBeAg** is the best indicator of high viral replication and high infectivity. * **Chronic Infection:** Defined by the persistence of HBsAg for >6 months. * **Post-Transfusion Hepatitis:** While HBV can be transmitted via blood, **Hepatitis C (HCV)** was historically the most common cause of post-transfusion hepatitis before rigorous screening; however, HBV remains a high-yield topic for serological interpretation.

Q: All of the following viruses contain double-stranded DNA, except:

Parvovirus. **Explanation:** The fundamental rule of virology is that most DNA viruses are double-stranded (dsDNA) and most RNA viruses are single-stranded (ssRNA). However, there are two high-yield exceptions frequently tested in NEET-PG: **Parvoviridae** (the only medically important ssDNA virus) and **Reoviridae** (the only medically important dsRNA virus). 1. **Why Parvovirus is correct:** Parvovirus B19 belongs to the Parvoviridae family. It is a small, non-enveloped virus characterized by a **single-stranded DNA (ssDNA)** genome. This makes it the unique exception among the DNA viruses listed. 2. **Why the other options are incorrect:** * **Papilloma virus:** A member of the Papovaviridae family; it contains circular dsDNA. * **Herpes virus:** A large, enveloped virus containing linear dsDNA. * **Pox virus:** The largest and most complex virus; despite replicating in the cytoplasm (an exception for DNA viruses), it contains a linear dsDNA genome. **Clinical Pearls for NEET-PG:** * **Parvovirus B19:** Causes **Erythema Infectiosum** (Fifth disease), characterized by the "slapped-cheek" rash. It targets erythroid progenitor cells, leading to **Aplastic Crisis** in patients with chronic hemolytic anemias (e.g., Sickle Cell Disease) and **Hydrops Fetalis** if contracted during pregnancy. * **Mnemonic for DNA Viruses:** "**HHAPPPPy**" (Herpes, Hepadna, Adeno, Papilloma, Polyoma, Pox, Parvo). All are dsDNA except **Parvo** (ssDNA). All are icosahedral except **Pox** (complex). All replicate in the nucleus except **Pox** (cytoplasm).

Question 1

A 9-year-old boy presents with a severe sore throat, fever, and dysphagia. Physical examination reveals grayish-white papulovesicular lesions on an erythematous base that have ulcerated. The lesions are located on the soft palate, anterior pillars of the tonsils, and uvula, but not on the gingiva, tongue, or lips. A clinical diagnosis of herpangina is made. Which of the following is the most likely causative organism?

Accepted Answer

Coxsackievirus A

Answer

Measles (Morbillivirus)

Answer

Rubella (Rubivirus)

Answer

Herpes simplex virus-1 (HSV-1)

Question 2

The recent avian flu outbreak is caused by which of the following strains?

Accepted Answer

H5N1

Answer

H1N1

Answer

H7N9

Answer

H7N7

Question 3

Which of the following statements is true regarding human metapneumovirus?

Accepted Answer

It is a segmented negative-sense single-stranded RNA virus.

Answer

Its incidence accounts for 5% of all respiratory infections.

Answer

It spreads through sexual contact and blood transfusion.

Answer

It contains NS1 and NS2 antigens.

Question 4

The Hella cell line belongs to which category of cell culture?

Accepted Answer

Continuous cell line

Answer

Primary cell culture

Answer

Diploid cell strains

Answer

Tissue culture

Question 5

Which of the following microorganisms commonly shows antigenic drift in its pathogenicity?

Accepted Answer

Influenza virus

Answer

Cholera

Answer

Diphtheria

Answer

Plague

Question 6

What is the usual causative agent of infection in renal transplant patients?

Accepted Answer

Cytomegalovirus (CMV)

Answer

Human Immunodeficiency Virus (HIV)

Answer

Herpes Simplex Virus

Answer

Salmonella species

Question 7

A 33-year-old male with AIDS and a history of shingles develops a severe, multifocal encephalitis. Therapy is instituted with acyclovir, but the man dies on the fourth day of his hospital admission. Which of the following viruses is the most likely cause of his encephalitis?

Accepted Answer

Herpes zoster-varicella

Answer

Cytomegalovirus

Answer

Herpes simplex type I

Answer

Herpes simplex type II

Question 8

Which of the following flaviviruses is closely related to the Russian spring-summer encephalitis virus?

Accepted Answer

Kyasanur Forest Disease (KFD)

Answer

Dengue

Answer

Chikungunya

Answer

Yellow fever

Question 9

A patient presented with features of acute hepatitis following a blood transfusion a few weeks ago. Which of the following serological markers indicates the acute phase of hepatitis B infection?

Accepted Answer

Anti HBc positive, HBsAg positive

Answer

Anti HBe positive, HBsAg positive

Answer

Anti HBs positive, HBsAg negative

Answer

HBeAg negative, HBsAg negative

Question 10

All of the following viruses contain double-stranded DNA, except:

Accepted Answer

Parvovirus

Answer

Papilloma virus

Answer

Herpes virus

Answer

Pox virus

Virology — MCQs

Virology — MCQs

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