Virology Practice Questions

Q: Recurrent herpes simplex infection occurs due to:

Latent virus in the nerve ganglia. ### Explanation **Correct Answer: C. Latent virus in the nerve ganglia** **Mechanism of Latency and Recurrence:** Herpes Simplex Virus (HSV-1 and HSV-2) exhibits a unique life cycle characterized by **latency**. During the primary infection, the virus replicates in the mucoepithelial cells. From there, it travels via **retrograde axonal transport** along sensory nerve fibers to the sensory nerve ganglia. * **HSV-1** typically remains latent in the **Trigeminal ganglion**. * **HSV-2** typically remains latent in the **Sacral ganglia**. In these ganglia, the viral genome persists in an episomal form without killing the host cell. Upon triggers like stress, UV light, fever, or immunosuppression, the virus undergoes **reactivation**, travels via **anterograde transport** back down the nerve to the skin/mucosa, and causes recurrent lesions (e.g., Herpes Labialis). **Why other options are incorrect:** * **Option A & B:** The virus does not remain latent in the oral mucosa or the skin. While these are the sites of active replication and clinical manifestation, the virus is cleared from these peripheral tissues by the immune system. It only survives long-term by "hiding" in the immunologically privileged site of the nervous system. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnostic Gold Standard:** Viral Culture (though PCR is now more sensitive). * **Tzanck Smear:** Shows **Multinucleated Giant Cells** and **Cowdry Type A** intranuclear inclusion bodies (characteristic but not specific for HSV). * **Drug of Choice:** Acyclovir (inhibits viral DNA polymerase). * **HSV-1** is the most common cause of **Sporadic Viral Encephalitis** (affects the temporal lobe). * **HSV-2** is a common cause of **Aseptic Meningitis**.

Q: Which of the following causes a fatal encephalitis for which a vaccine is available?

Rabies. **Explanation:** **Rabies virus** (Option A) is the correct answer because it causes an acute, progressive, and almost invariably fatal encephalitis once clinical symptoms appear. It is a Rhabdovirus transmitted typically via the saliva of an infected animal. Crucially, it is a vaccine-preventable disease. Both pre-exposure prophylaxis (for high-risk individuals) and post-exposure prophylaxis (PEP) are highly effective if administered before the onset of symptoms. **Analysis of Incorrect Options:** * **Rhinovirus (Option B):** The primary cause of the common cold. It is restricted to the upper respiratory tract and does not cause encephalitis. There is no vaccine due to the high number of serotypes. * **Cytomegalovirus (Option C):** While CMV can cause encephalitis in immunocompromised patients (e.g., AIDS), it is not "invariably fatal" in the general population. Currently, there is no commercially available vaccine for CMV. * **Respiratory Syncytial Virus (Option D):** A major cause of bronchiolitis and pneumonia in infants. It does not typically cause encephalitis, and while vaccines have recently been approved for specific populations (older adults/maternal use), it does not fit the "fatal encephalitis" profile. **High-Yield NEET-PG Pearls:** * **Negri Bodies:** Pathognomonic intracytoplasmic eosinophilic inclusions found in pyramidal cells of the hippocampus and Purkinje cells of the cerebellum. * **Mechanism:** The virus binds to **Nicotinic Acetylcholine Receptors (nAChR)** at the neuromuscular junction and travels via retrograde axonal transport to the CNS. * **Vaccine Type:** Modern rabies vaccines (e.g., PCECV, HDCV) are **inactivated/killed** vaccines. * **Hydrophobia:** Characteristic symptom due to painful spasms of the laryngeal and pharyngeal muscles when attempting to swallow.

Q: Which one of the following viruses is the leading cause of congenital malformations?

Cytomegalovirus. **Explanation:** **Cytomegalovirus (CMV)** is the correct answer as it is the **most common cause of congenital viral infections** worldwide. It belongs to the *Betaherpesvirinae* subfamily. While most maternal infections are asymptomatic, primary infection during pregnancy poses the highest risk of vertical transmission to the fetus. **Why CMV is the correct answer:** CMV is the leading infectious cause of sensorineural hearing loss and intellectual disability. The classic clinical triad of congenital CMV includes **chorioretinitis, periventricular calcifications, and microcephaly**. Other features include "blueberry muffin" rash (extramedullary hematopoiesis), hepatosplenomegaly, and jaundice. **Why the other options are incorrect:** * **Rabies virus:** This is a neurotropic rhabdovirus transmitted via animal bites. It causes fatal encephalitis but is not associated with congenital malformations. * **Rhinovirus:** The most common cause of the "common cold," it remains localized to the upper respiratory tract and does not cause viremia leading to fetal infection. * **Respiratory Syncytial Virus (RSV):** A major cause of bronchiolitis and pneumonia in infants, but it is acquired postnatally and is not a teratogenic virus. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** The gold standard for congenital CMV is detecting the virus in **urine or saliva** via PCR or culture within the first 3 weeks of life. * **Histology:** Look for **"Owl’s eye" intranuclear inclusion bodies** in biopsy specimens. * **TORCH infections:** CMV is a key member of the TORCH group (Toxoplasmosis, Others, Rubella, CMV, Herpes). * **Treatment:** Intravenous **Ganciclovir** or oral Valganciclovir is used to reduce the severity of hearing loss and developmental delays.

Q: Kyanasur forest disease is transmitted by which vector?

Haema physalis spinigera. **Explanation:** **Kyasanur Forest Disease (KFD)**, commonly known as "Monkey Fever," is a viral hemorrhagic fever endemic to the South Indian state of Karnataka. It is caused by the KFD virus, a member of the family *Flaviviridae*. 1. **Why Option A is Correct:** The primary vector for KFD is the **hard tick**, specifically ***Haemaphysalis spinigera***. Humans typically contract the infection through the bite of an infected nymphal tick or via contact with an infected animal (most notably monkeys like Langurs and Bonnet macaques, which act as sentinel animals). 2. **Why Other Options are Incorrect:** * **Option B (Culex vishnui):** This is the principal vector for **Japanese Encephalitis (JE)**. While it is a mosquito-borne Flavivirus, it is not involved in KFD transmission. * **Option C (Aedes):** *Aedes aegypti* and *Aedes albopictus* are vectors for **Dengue, Chikungunya, Zika, and Yellow Fever**. * **Option D (Anopheles):** This mosquito genus is the definitive host and vector for **Malaria**. **High-Yield Clinical Pearls for NEET-PG:** * **Reservoirs:** Wild rodents are the natural reservoirs; monkeys are the amplifying hosts (high mortality in monkeys precedes human outbreaks). * **Clinical Presentation:** Characterized by sudden onset high fever, frontal headache, severe myalgia, and hemorrhagic manifestations. A "bimodal" illness pattern is often seen (fever followed by a brief afebrile period, then neurological symptoms). * **Diagnosis:** PCR (early phase) or IgM ELISA. * **Prevention:** A **formalin-inactivated vaccine** is available and used in endemic areas of Karnataka.

Q: Coxsackie A virus causes all except:

Bornholm's disease. **Explanation:** The question asks for the condition *not* caused by Coxsackie A virus. The correct answer is **Bornholm’s disease**, which is classically associated with **Coxsackie B virus**. **1. Why Bornholm’s disease is the correct answer:** Bornholm’s disease (also known as epidemic pleurodynia or "Devil’s Grip") is characterized by sudden onset of severe, paroxysmal chest and upper abdominal pain due to inflammation of the intercostal muscles. This condition is a hallmark clinical manifestation of **Group B Coxsackieviruses**, not Group A. **2. Analysis of incorrect options (Diseases caused by Coxsackie A):** * **Herpangina:** Characterized by fever, sore throat, and vesiculopapular lesions on the posterior oropharynx (tonsils and soft palate). It is a classic presentation of Coxsackie A. * **Hand, Foot, and Mouth Disease (HFMD):** Presents with vesicular eruptions on the palms, soles, and oral mucosa. While Enterovirus 71 can also cause it, **Coxsackie A16** is the most common etiology. * **Aseptic Meningitis:** Both Coxsackie A and B are leading causes of viral (aseptic) meningitis. **Clinical Pearls for NEET-PG:** * **Mnemonic for Coxsackie A:** "A" for **A**ngina (Herpangina) and **A**ppendages (Hand, Foot, and Mouth). * **Mnemonic for Coxsackie B:** "B" for **B**ody (Bornholm’s), **B**eating (Myocarditis/Pericarditis), and **B**eta cells (linked to Type 1 Diabetes). * **High-Yield Fact:** Coxsackie B is the most common viral cause of **myocarditis** and **pericarditis**. * Both groups belong to the *Picornaviridae* family and are non-enveloped, positive-sense ssRNA viruses.

Q: Roseola infantum is most commonly caused by which of the following?

Human Herpesvirus 6. **Explanation:** **Roseola Infantum**, also known as **Exanthema Subitum** or Sixth Disease, is a common childhood febrile illness. The primary causative agent is **Human Herpesvirus 6 (HHV-6)**, specifically variant HHV-6B. It typically affects children between 6 months and 2 years of age. The classic clinical presentation involves a high-grade fever (often >39.5°C) lasting for 3 to 5 days, which subsides abruptly, followed immediately by the appearance of a pink, maculopapular rash starting on the trunk and spreading to the face and extremities. **Analysis of Options:** * **Option A (HHV-2):** This is the primary cause of genital herpes and neonatal herpes; it does not cause Roseola. * **Option C (HHV-7):** While HHV-7 can cause Roseola infantum, it is much less common than HHV-6. It usually occurs in slightly older children. * **Option D (HHV-8):** This virus is the causative agent of Kaposi Sarcoma, Primary Effusion Lymphoma, and Multicentric Castleman Disease. **Clinical Pearls for NEET-PG:** * **The "Fever then Rash" Rule:** Roseola is the only childhood exanthem where the rash appears *after* the fever disappears (defervescence). * **Nagayama Spots:** Small erythematous papules on the soft palate and uvula seen in some patients. * **Complications:** HHV-6 is highly neurotropic; Roseola is a leading cause of **febrile seizures** in infants due to the rapid rise in temperature. * **Treatment:** Usually self-limiting; supportive care is sufficient. Ganciclovir may be used in immunocompromised patients.

Q: Which of the following statements is true of Rabies?

Fluorescent antibody is the test of choice. **Explanation:** **1. Why Option A is Correct:** The **Direct Fluorescent Antibody (DFA)** test is considered the "gold standard" and the test of choice for diagnosing rabies in both animals and humans. It detects rabies virus antigens in brain tissue (post-mortem) or skin biopsies from the nape of the neck (ante-mortem). It is highly sensitive, specific, and provides rapid results, which is critical for clinical decision-making. **2. Why Other Options are Incorrect:** * **Option B:** Human Diploid Cell Vaccine (HDCV) is an **inactivated (killed)** vaccine, not live attenuated. All modern rabies vaccines used in humans (HDCV, PCECV, PVRV) are inactivated. * **Option C:** Rabies vaccines must be administered **intramuscularly in the deltoid region** (adults) or anterolateral thigh (children). It should **never** be given in the gluteal region (buttock) because the thick overlying fat layer can lead to poor absorption and lower neutralizing antibody titers. * **Option D:** Local wound care is the **most important first step** in post-exposure prophylaxis (PEP). Immediate flushing and washing of the wound with soap and water for at least 15 minutes can reduce the viral load at the site by up to 80%. **Clinical Pearls for NEET-PG:** * **Negri Bodies:** Intracytoplasmic eosinophilic inclusion bodies found most commonly in **Hippocampus (Ammon’s horn)** and Cerebellum (Purkinje cells). * **Street Virus:** Freshly isolated from natural cases; has a long incubation period and produces Negri bodies. * **Fixed Virus:** Adapted by serial passage in brains; has a short, fixed incubation period (4–6 days) and does **not** produce Negri bodies. * **Post-Exposure Prophylaxis (PEP):** Includes wound care, Rabies Immunoglobulin (RIG), and vaccination (Essen or Thai Red Cross regimen).

Q: A 1-month-old baby presents with microcephaly and hepatosplenomegaly. A Giemsa-stained urine sample shows owl's eye inclusion bodies. What is the diagnosis?

Cytomegalovirus (CMV). ### Explanation **Correct Answer: A. Cytomegalovirus (CMV)** The clinical presentation of **microcephaly** and **hepatosplenomegaly** in a neonate, combined with the pathognomonic finding of **"Owl’s eye" inclusion bodies**, is diagnostic of **Congenital Cytomegalovirus infection**. CMV is the most common intrauterine infection. The "Owl's eye" appearance refers to large, **intranuclear, basophilic inclusion bodies** surrounded by a clear halo, typically found in renal tubular epithelial cells (hence detectable in urine) or vascular endothelial cells. **Why other options are incorrect:** * **Epstein-Barr virus (EBV):** Primarily causes Infectious Mononucleosis. While it can cause hepatosplenomegaly, it is not a classic cause of congenital microcephaly and is characterized by **atypical lymphocytes (Downey cells)** on blood smear, not owl's eye inclusions. * **Herpes simplex virus (HSV):** Congenital HSV typically presents with the triad of skin vesicles, eye involvement (chorioretinitis), and CNS abnormalities. Histology shows **Cowdry Type A** inclusions. * **Varicella zoster virus (VZV):** Congenital Varicella Syndrome is characterized by **cicatricial skin scarring**, limb hypoplasia, and rudimentary digits, rather than the specific inclusion bodies described. --- ### High-Yield Clinical Pearls for NEET-PG: * **Most common** cause of sensorineural hearing loss (SNHL) and mental retardation among congenital infections. * **Classic Triad:** Microcephaly, Periventricular calcifications, and Hepatosplenomegaly/Petechiae ("Blueberry muffin rash"). * **Diagnosis:** Culture or PCR of saliva/urine within the first 3 weeks of life is the gold standard. * **Treatment:** Ganciclovir or Valganciclovir is used to reduce the severity of hearing loss and developmental delay. * **Histology Note:** Do not confuse "Owl's eye" appearance of CMV with the "Owl's eye" nuclei of **Reed-Sternberg cells** in Hodgkin Lymphoma.

Q: A student developed fever, nausea, vomiting, and diarrhea after consuming shellfish. What is the most likely causative agent?

Norwalk virus. ### Explanation **Correct Option: B. Norwalk virus (Norovirus)** The clinical presentation of acute gastroenteritis (fever, nausea, vomiting, and diarrhea) following the consumption of **shellfish** (especially raw oysters) is a classic association for **Norovirus**. * **Mechanism:** Noroviruses are highly contagious, low-infectious-dose members of the *Caliciviridae* family. They are the leading cause of epidemic non-bacterial gastroenteritis worldwide. * **Transmission:** While the fecal-oral route is primary, outbreaks are frequently linked to contaminated water and seafood (shellfish concentrate the virus from contaminated water). **Why other options are incorrect:** * **A. Adenovirus:** Serotypes 40 and 41 cause gastroenteritis, primarily in children. It is not typically associated with shellfish outbreaks. * **C. Enterovirus:** While transmitted via the fecal-oral route, these viruses (like Polio, Coxsackie) more commonly cause systemic illnesses, rashes, or meningitis rather than isolated acute diarrheal disease. * **D. Rotavirus:** This is the most common cause of severe dehydrating diarrhea in **infants and young children**. While it causes similar symptoms, it is not the classic agent associated with adult outbreaks linked to shellfish. **High-Yield Clinical Pearls for NEET-PG:** * **Norovirus** is the most common cause of gastroenteritis outbreaks on **cruise ships**, in schools, and in nursing homes. * **Key Buzzword:** "Shellfish/Oysters" + "Vomiting/Diarrhea" = Norovirus (or *Vibrio parahaemolyticus* if bacterial). * **Resistance:** Noroviruses are resistant to many common disinfectants, including alcohol-based hand sanitizers; handwashing with soap and water is preferred. * **Seasonality:** Often referred to as the "Winter Vomiting Bug."

Question 1

Recurrent herpes simplex infection occurs due to:

Accepted Answer

Latent virus in the nerve ganglia

Answer

Virus residing in the oral mucosa

Answer

Latent virus in the skin supplying the affected area

Answer

None of the above

Question 2

Which of the following causes a fatal encephalitis for which a vaccine is available?

Accepted Answer

Rabies

Answer

Rhinovirus

Answer

Cytomegalovirus

Answer

Respiratory syncytial virus

Question 3

What is a characteristic of chickenpox?

Accepted Answer

It may be severe in a newborn infected by the mother in late pregnancy.

Answer

It is commonly seen in a congenital form.

Answer

It affects the limbs more than the trunk.

Answer

It may cause pneumonitis.

Question 4

Which one of the following viruses is the leading cause of congenital malformations?

Accepted Answer

Cytomegalovirus

Answer

Rabies virus

Answer

Rhinovirus

Answer

Respiratory syncytial virus

Question 5

Kyanasur forest disease is transmitted by which vector?

Accepted Answer

Haema physalis spinigera

Answer

Culex vishnui

Answer

Aedes

Answer

Anopheles

Question 6

Coxsackie A virus causes all except:

Accepted Answer

Bornholm's disease

Answer

Aseptic meningitis

Answer

Herpangina

Answer

Hand foot and mouth disease

Question 7

Roseola infantum is most commonly caused by which of the following?

Accepted Answer

Human Herpesvirus 6

Answer

Human Herpesvirus 2

Answer

Human Herpesvirus 7

Answer

Human Herpesvirus 8

Question 8

Which of the following statements is true of Rabies?

Accepted Answer

Fluorescent antibody is the test of choice

Answer

HDCV is a live attenuated vaccine

Answer

Vaccine is given deep IM in the buttock

Answer

Local wound care is of no use

Question 9

A 1-month-old baby presents with microcephaly and hepatosplenomegaly. A Giemsa-stained urine sample shows owl's eye inclusion bodies. What is the diagnosis?

Accepted Answer

Cytomegalovirus (CMV)

Answer

Epstein-Barr virus (EBV)

Answer

Herpes simplex virus

Answer

Varicella zoster virus

Question 10

A student developed fever, nausea, vomiting, and diarrhea after consuming shellfish. What is the most likely causative agent?

Accepted Answer

Norwalk virus

Answer

Adenovirus

Answer

Enterovirus

Answer

Rotavirus

Virology — MCQs

Virology — MCQs

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