Virology Practice Questions

Q: SSPE is a rare complication of which viral infection?

Measles. **Explanation:** **Subacute Sclerosing Panencephalitis (SSPE)**, also known as Dawson disease, is a progressive, fatal neurodegenerative disease caused by a persistent infection with a **defective Measles virus**. **Why Measles is Correct:** SSPE occurs years (typically 5–10) after an initial measles infection, usually in children who contracted the virus before age two. The underlying mechanism involves a mutated measles virus that lacks the **M (Matrix) protein**, preventing the virus from budding. Instead, it spreads directly from cell to cell via syncytia formation, leading to widespread inflammation and demyelination in the CNS. **Analysis of Incorrect Options:** * **Mumps:** While mumps can cause acute viral meningitis or encephalitis, it does not lead to a chronic, progressive sclerosing panencephalitis like SSPE. * **Rubella:** Rubella is associated with **Progressive Rubella Panencephalitis (PRP)**, which is clinically similar to SSPE but much rarer and caused by the Rubella virus, not Measles. * **Influenza:** Influenza is associated with acute neurological complications like Reye Syndrome (if aspirin is used) or acute necrotizing encephalopathy, but not chronic persistent CNS infections. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** Characterized by high titers of **anti-measles antibodies** in the CSF and serum (intrathecal synthesis). * **EEG Finding:** Pathognomonic **periodic, high-voltage slow-wave complexes** (Radermecker complexes). * **Histology:** Presence of **Cowdry Type A** intranuclear inclusion bodies in neurons and glial cells. * **Clinical Stages:** Progresses from behavioral changes to myoclonic jerks, followed by dementia and eventually a vegetative state.

Q: Which of the following statements is true regarding chickenpox?

The virus is not found in the scabs.. **Explanation:** Chickenpox is caused by the **Varicella-Zoster Virus (VZV)**, a member of the *Herpesviridae* family. Understanding its transmission and virology is crucial for NEET-PG. **1. Why Option A is Correct:** The Varicella-Zoster virus is highly fragile and thermolabile. While the virus is present in high concentrations in the **vesicular fluid** and upper respiratory secretions, it is **not found in the scabs (crusts)**. The scabs consist of dried exudate and dead epithelial cells; by the time a lesion reaches the crusting stage, the virus has been inactivated. Therefore, a patient is no longer infectious once all lesions have crusted over. **2. Why the other options are Incorrect:** * **Option B:** Unlike many other viruses (like Influenza), VZV **cannot be grown on chick embryos**. It is highly host-specific and is typically cultured in human diploid cell lines (e.g., WI-38 or MRC-5). * **Option C:** VZV is a **DNA virus** (specifically, a double-stranded, enveloped DNA virus), not an RNA virus. * **Option D:** VZV **can cross the placental barrier**. Infection in the first 20 weeks of pregnancy can lead to **Congenital Varicella Syndrome** (characterized by cicatricial skin scarring, limb hypoplasia, and chorioretinitis). **Clinical Pearls for NEET-PG:** * **Secondary Attack Rate:** Very high (~90%) among susceptible household contacts. * **Incubation Period:** Usually 14–16 days (Range: 10–21 days). * **Period of Communicability:** 1–2 days before the appearance of the rash until all lesions have crusted (usually 4–5 days after rash onset). * **Rash Pattern:** Centripetal distribution (more on trunk) and "pleomorphic" (all stages of rash—papules, vesicles, and crusts—seen simultaneously). * **Dew-drop on a rose petal:** Classic description of the varicella vesicle.

Q: Which of the following infections is not documented to be spread by sexual contact?

Hepatitis E Virus (HEV). ### Explanation The correct answer is **Hepatitis E Virus (HEV)**. **1. Why Hepatitis E (HEV) is the correct answer:** Hepatitis E is primarily transmitted via the **fecal-oral route**, most commonly through contaminated drinking water. Unlike other hepatitis viruses, there is currently **no documented evidence** of HEV transmission through sexual contact. It is characterized by epidemic outbreaks in developing countries and carries a high mortality rate (up to 20%) specifically in pregnant women. **2. Why the other options are incorrect:** * **Hepatitis B (HBV):** This is a classic sexually transmitted infection (STI). It is found in high concentrations in blood, semen, and vaginal secretions. Sexual contact is a major route of transmission globally. * **Hepatitis C (HCV):** While primarily blood-borne (parenteral), sexual transmission of HCV is documented, particularly among men who have sex with men (MSM) and individuals with multiple sexual partners or co-infection with HIV. * **Hepatitis A (HAV):** Although primarily fecal-oral, HAV is well-documented to spread via **sexual contact**, specifically through oral-anal contact (anilingus). Outbreaks are frequently reported in the MSM community. **3. NEET-PG High-Yield Pearls:** * **Vowels (A & E):** Transmitted by the **Enteric** route (Fecal-oral). * **Consonants (B, C, D):** Transmitted by **Blood** and Body fluids (Parenteral/Sexual). * **Exception to remember:** While both A and E are enteric, **only A** is significantly associated with sexual transmission (oral-anal). * **Pregnancy & HEV:** Always remember the association of HEV with **Fulminant Hepatic Failure** in the third trimester of pregnancy. * **HCV:** Has the highest risk of progressing to **chronic** hepatitis and cirrhosis.

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.

Question 1

SSPE is a rare complication of which viral infection?

Accepted Answer

Measles

Answer

Mumps

Answer

Rubella

Answer

Influenza

Question 2

Which of the following statements is true regarding chickenpox?

Accepted Answer

The virus is not found in the scabs.

Answer

The virus can be grown on chick embryo.

Answer

It is caused by an RNA virus.

Answer

It does not cross the placental barrier.

Question 3

Which of the following infections is not documented to be spread by sexual contact?

Accepted Answer

Hepatitis E Virus (HEV)

Answer

Hepatitis A Virus (HAV)

Answer

Hepatitis B Virus (HBV)

Answer

Hepatitis C Virus (HCV)

Question 4

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 5

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

Accepted Answer

H5N1

Answer

H1N1

Answer

H7N9

Answer

H7N7

Question 6

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 7

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 8

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

Accepted Answer

Influenza virus

Answer

Cholera

Answer

Diphtheria

Answer

Plague

Question 9

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 10

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

Virology — MCQs

Virology — MCQs

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