Virology Practice Questions

Q: Cytomegalovirus (CMV) infection is common. Which one of the following statements best characterizes CMV?

It can be transmitted across the placental barrier. **Explanation:** **1. Why Option A is Correct:** Cytomegalovirus (CMV), a member of the *Betaherpesvirinae* subfamily, is the most common cause of **congenital viral infection**. It can cross the placental barrier during both primary maternal infection and reactivation. Transmission can occur in utero (transplacental), during delivery (birth canal), or postpartum (breast milk). Congenital CMV is a leading cause of sensorineural hearing loss and intellectual disability. **2. Why the Other Options are Incorrect:** * **Option B:** Most CMV infections in immunocompetent individuals are **asymptomatic** or present as a mild mononucleosis-like syndrome (heterophile antibody negative). Symptomatic disease is primarily seen in neonates and immunocompromised patients. * **Option C:** CMV has a tropism for **mononuclear cells** (lymphocytes and monocytes) and polymorphonuclear leukocytes, not red blood cells. It establishes latency in myeloid progenitor cells in the bone marrow. * **Option D:** CMV is notorious for **reactivation** during periods of immunosuppression. It is a major cause of morbidity in transplant recipients (causing "CMV syndrome," pneumonia, or hepatitis) and AIDS patients (causing retinitis or colitis). **Clinical Pearls for NEET-PG:** * **Histology:** Look for **"Owl’s eye" appearance** (large intranuclear inclusion bodies with a clear halo). * **Congenital CMV Triad:** Chorioretinitis, periventricular calcifications, and microcephaly. * **Diagnosis:** PCR is the gold standard for systemic infection; Shell vial culture is a rapid culture technique. * **Treatment:** **Ganciclovir** is the drug of choice; Foscarnet is used for resistant cases.

Q: What are the most common types of human papillomavirus (HPV) causing cervical cancer?

16 and 18. **Explanation:** Cervical cancer is primarily caused by persistent infection with **High-Risk Human Papillomavirus (hrHPV)**. Among the various oncogenic strains, **HPV 16 and 18** are the most significant, accounting for approximately **70% of all cervical cancer cases** worldwide. HPV 16 is the most common (linked to squamous cell carcinoma), while HPV 18 has a higher association with adenocarcinoma. These strains produce E6 and E7 oncoproteins, which inhibit the tumor suppressor proteins p53 and pRb, respectively, leading to uncontrolled cell proliferation. **Analysis of Options:** * **Option A (Correct):** HPV 16 and 18 are the primary high-risk types responsible for the majority of cervical malignancies. * **Option B:** While HPV 33 is a high-risk type, HPV 1 is associated with benign cutaneous warts (verruca plantaris). * **Option C:** HPV 6 and 11 are **Low-Risk types**. They cause approximately 90% of genital warts (Condyloma acuminata) and recurrent respiratory papillomatosis, but they do not typically cause cancer. * **Option D:** HPV 2 is associated with common skin warts (verruca vulgaris); HPV 14 is not a major clinical subtype in this context. **High-Yield Clinical Pearls for NEET-PG:** * **Most common HPV type in Cervical Cancer:** HPV 16. * **Most common HPV type in Adenocarcinoma:** HPV 18. * **HPV Vaccines:** The Quadrivalent vaccine (Gardasil) targets 6, 11, 16, and 18. The Nonavalent vaccine adds 31, 33, 45, 52, and 58. * **Screening:** The primary screening tool is the Pap smear (cytology) and hrHPV DNA testing. The transformation zone is the most common site for cervical carcinogenesis.

Q: Which virus is transmitted by the same arthropod that transmits babesiosis and ehrlichiosis?

Tick-borne encephalitis virus. ### Explanation The core concept tested here is the identification of diseases sharing a common vector. **Babesiosis** (*Babesia microti*) and **Ehrlichiosis** (specifically Human Granulocytic Anaplasmosis caused by *Anaplasma phagocytophilum*) are both transmitted by **Ixodes ticks** (hard ticks). **Why Tick-borne encephalitis virus (TBEV) is correct:** TBEV belongs to the *Flaviviridae* family and is primarily transmitted by the bite of infected **Ixodes ticks** (*I. ricinus* and *I. persulcatus*). Since Babesiosis, Ehrlichiosis, and TBEV (along with Lyme disease) all utilize the *Ixodes* species as their primary arthropod vector, they are often found in the same geographical distributions and can occasionally cause co-infections. **Why the other options are incorrect:** * **A. Human papillomavirus (HPV):** Transmitted via direct skin-to-skin or sexual contact; it has no arthropod vector. * **B. West Nile virus:** While it is an arbovirus, it is transmitted by **Culex mosquitoes**, not ticks. * **D. Polyomavirus:** (e.g., JC and BK viruses) These are typically transmitted through respiratory droplets or contaminated water; they are not vector-borne. **NEET-PG High-Yield Pearls:** * **Ixodes Tick "Big Four":** Always remember the four major pathogens transmitted by *Ixodes*: **L**yme disease (*Borrelia burgdorferi*), **B**abesiosis, **E**hrlichiosis/Anaplasmosis, and **T**ick-borne encephalitis (**Mnemonic: BELT**). * **Vector Differentiation:** * *Culex:* West Nile, Japanese Encephalitis, Filariasis. * *Aedes:* Dengue, Chikungunya, Zika, Yellow Fever. * *Ticks:* Kyasanur Forest Disease (KFD) is the major tick-borne viral hemorrhagic fever in India (transmitted by *Haemaphysalis spinigera*).

Q: Which hepatitis virus is notorious for causing chronic hepatitis evolving to cirrhosis?

HCV. **Explanation:** The correct answer is **HCV (Hepatitis C Virus)**. The hallmark of HCV infection is its high propensity for chronicity. Unlike other hepatitis viruses, approximately **75%–85%** of individuals infected with HCV fail to clear the virus and develop chronic infection. Over a period of 20 years, about 20% of these chronic cases progress to **cirrhosis**, which significantly increases the risk of Hepatocellular Carcinoma (HCC). **Analysis of Options:** * **HBV (Hepatitis B Virus):** While HBV is a major cause of chronic hepatitis and cirrhosis worldwide, the rate of chronicity in adults is relatively low (only **5%–10%**). It is more notorious for causing cirrhosis in neonatal transmissions (90% chronicity). * **HEV (Hepatitis E Virus):** This is typically an acute, self-limiting infection spread via the fecal-oral route. It does not cause chronic hepatitis in immunocompetent individuals, though it is notorious for high mortality in **pregnant women**. * **HAV (Hepatitis A Virus):** HAV causes only acute hepatitis and **never** progresses to a chronic state or cirrhosis. **High-Yield NEET-PG Pearls:** * **Most common indication for liver transplant:** HCV-induced cirrhosis [1]. * **HCV Screening:** Anti-HCV antibody is the screening test; **HCV-RNA** (PCR) is the gold standard for confirming active infection [1]. * **Extrahepatic manifestations of HCV:** Mixed cryoglobulinemia, Membranoproliferative glomerulonephritis (MPGN), and Porphyria cutanea tarda. * **Rule of 80s for HCV:** 80% become chronic, 80% are asymptomatic, and (historically) 80% were genotype 1 [1].

Q: What is the least common cause of sporadic encephalitis?

Rhinovirus. The correct answer is **D. Rhinovirus**. **Medical Concept:** Sporadic encephalitis refers to isolated cases of brain inflammation occurring year-round, independent of seasonal outbreaks. While many viruses are neurotropic (capable of infecting nerve tissue), **Rhinovirus** is primarily restricted to the upper respiratory tract. It thrives at temperatures slightly below core body temperature (33–35°C) and lacks the typical mechanisms to cross the blood-brain barrier. While extremely rare case reports exist in immunocompromised individuals, it is not considered a standard or recognized cause of sporadic encephalitis in clinical practice. **Analysis of Options:** * **HSV (Option A):** Herpes Simplex Virus-1 is the **most common cause** of sporadic fatal encephalitis worldwide [1]. It typically involves the temporal lobes [1]. * **VZV (Option B):** Varicella-Zoster Virus is a significant cause of sporadic encephalitis, often occurring during primary infection (chickenpox) or reactivation (shingles), frequently associated with vasculopathy. * **Arboviruses (Option C):** While many arboviruses (like Japanese Encephalitis) are epidemic/seasonal, several can present sporadically depending on geographic location and vector prevalence. They are well-established neurotropic pathogens. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of sporadic encephalitis:** HSV-1. * **Most common cause of epidemic encephalitis in India:** Japanese Encephalitis (JE) virus. * **Gold Standard Diagnosis:** CSF PCR for viral DNA/RNA. * **Imaging Choice:** MRI is superior to CT; look for temporal lobe involvement in HSV [1]. * **Treatment:** Empiric Acyclovir should be started immediately if encephalitis is suspected.

Q: What is the most specific diagnostic test for AIDS?

Western blot. **Explanation:** The diagnosis of HIV/AIDS follows a specific two-step algorithm: screening followed by confirmation. **Why Western Blot is the Correct Answer:** Western blot is considered the **gold standard confirmatory test** for HIV because of its high **specificity**. While screening tests look for general reactivity, the Western blot detects specific antibodies against individual HIV proteins (such as gp120, gp41, and p24). A positive result requires the presence of bands against multiple specific viral antigens, virtually eliminating false positives. **Analysis of Incorrect Options:** * **ELISA (Option C):** This is the **standard screening test**. It is highly sensitive (to ensure no cases are missed) but has lower specificity than Western blot, meaning it can occasionally yield false positives due to cross-reacting antibodies. * **Southern Blot (Option B):** This laboratory technique is used to detect specific **DNA** sequences. It is not used in the routine clinical diagnosis of HIV/AIDS. * **Note on Current Trends:** While Western blot remains the traditional "most specific" answer for exams, modern NAAT (Nucleic Acid Amplification Test) for HIV RNA is now frequently used for early diagnosis and confirmation in clinical practice. **NEET-PG High-Yield Pearls:** 1. **Screening Test of Choice:** ELISA (High sensitivity). 2. **Confirmatory Test of Choice:** Western blot (High specificity). 3. **Window Period Test:** p24 antigen assay or HIV RNA (PCR) are the earliest markers detectable. 4. **Diagnosis in Infants (<18 months):** PCR is the gold standard because maternal IgG antibodies can cause false positives on ELISA/Western blot. 5. **Monitoring Progression:** CD4+ T-cell count is the best predictor of clinical progression, while Viral Load (HIV RNA) is the best monitor of treatment (ART) efficacy.

Q: Which antibodies are used to diagnose acute viral hepatitis A and E?

IgM anti-HAV and IgM anti-HEV. **Explanation:** The diagnosis of acute viral hepatitis relies on identifying markers of active infection. In clinical practice, **IgM (Immunoglobulin M)** is the hallmark of an **acute or recent infection**, whereas **IgG (Immunoglobulin G)** typically signifies **past exposure or immunity**. [1] 1. **Why Option A is correct:** Both Hepatitis A (HAV) and Hepatitis E (HEV) are transmitted via the fecal-oral route and cause acute, self-limiting hepatitis. **IgM anti-HAV** is the gold standard for diagnosing acute Hepatitis A [1]; it appears early in the course of the disease and usually becomes undetectable within 3 to 6 months. Similarly, **IgM anti-HEV** is the primary marker for diagnosing acute Hepatitis E. [1] 2. **Why other options are incorrect:** * **Option B:** IgG anti-HAV and IgG anti-HEV indicate past infection or long-term immunity (in the case of HAV, also post-vaccination). They do not differentiate a current acute illness from a previous one. [1] * **Option C:** Liver biopsy is rarely indicated for acute viral hepatitis. It is an invasive procedure reserved for cases of diagnostic uncertainty or chronic liver disease assessment. * **Option D:** While viruses are shed in the stool, this occurs during the late incubation period *before* the onset of clinical symptoms (jaundice). By the time a patient presents to a clinic, stool shedding has often ceased, making it a poor diagnostic tool. **High-Yield Clinical Pearls for NEET-PG:** * **Hepatitis E & Pregnancy:** HEV is notorious for causing **Fulminant Hepatic Failure** in pregnant women (especially in the 3rd trimester), with mortality rates reaching up to 20-25%. * **Hepatitis A:** It is the most common cause of acute viral hepatitis in children worldwide. It never progresses to chronicity. * **Window Period:** In Hepatitis B, the "window period" is diagnosed by **IgM anti-HBc**, as HBsAg and anti-HBs may both be negative.

Q: All the following viruses are transmitted by arthropod vectors except:

Hantavirus. **Explanation:** The core concept tested here is the distinction between **Arboviruses** (Arthropod-borne) and **Roboviruses** (Rodent-borne). **1. Why Hantavirus is the Correct Answer:** Hantavirus belongs to the *Bunyaviridae* family but is a **Robovirus**. It is transmitted to humans via the inhalation of aerosolized excreta (urine, feces, or saliva) from infected **rodents** (e.g., deer mice). It does not require an arthropod vector for transmission. Clinically, it causes two major syndromes: Hantavirus Pulmonary Syndrome (HPS) and Hemorrhagic Fever with Renal Syndrome (HFRS). **2. Why the other options are incorrect:** * **Dengue:** A Flavivirus transmitted by the *Aedes aegypti* mosquito. * **Chikungunya:** A Togavirus (Alphavirus) also transmitted primarily by *Aedes aegypti* and *Aedes albopictus*. * **Japanese Encephalitis (JE):** A Flavivirus transmitted by the *Culex tritaeniorhynchus* mosquito, commonly associated with rice fields. **High-Yield Clinical Pearls for NEET-PG:** * **Arboviruses:** Include members of *Flaviviridae* (Dengue, JE, West Nile, Zika, Yellow Fever), *Togaviridae* (Chikungunya), and *Bunyaviridae* (Crimean-Congo Hemorrhagic Fever). * **Roboviruses:** Include Hantavirus and Arenaviruses (Lassa fever). * **Hantavirus Exception:** While most *Bunyaviridae* are arboviruses, Hantavirus is the notable exception. * **Diagnosis:** Hantavirus is typically diagnosed via IgM ELISA or RT-PCR; remember the "triad" of HFRS: fever, hemorrhage, and acute renal failure.

Question 1

Cytomegalovirus (CMV) infection is common. Which one of the following statements best characterizes CMV?

Accepted Answer

It can be transmitted across the placental barrier

Answer

While a common infection, CMV is almost always symptomatic

Answer

The CMV can be cultured from red blood cells of infected patients

Answer

Unlike other viral infections, CMV is not activated by immunosuppressive therapy

Question 2

What are the most common types of human papillomavirus (HPV) causing cervical cancer?

Accepted Answer

16 and 18

Answer

1 and 33

Answer

6 and 11

Answer

2 and 14

Question 3

Which virus is transmitted by the same arthropod that transmits babesiosis and ehrlichiosis?

Accepted Answer

Tick-borne encephalitis virus

Answer

Human papillomavirus

Answer

West Nile virus

Answer

Polyomavirus

Question 4

Which hepatitis virus is notorious for causing chronic hepatitis evolving to cirrhosis?

Accepted Answer

HCV

Answer

HBV

Answer

HEV

Answer

HAV

Question 5

Viruses have various ways of entering the human body and producing disease. Which of the following descriptions accurately describes the route of transmission and target disease for the virus indicated?

Accepted Answer

Echovirus: fecal-oral; aseptic meningitis

Answer

Coronavirus: fecal-oral; peptic ulcers

Answer

HIV: respiratory droplet; anemia

Answer

Influenza virus: blood-borne; maculopapular rash

Question 6

What is the least common cause of sporadic encephalitis?

Accepted Answer

Rhinovirus

Answer

Herpes Simplex Virus (HSV)

Answer

Varicella-Zoster Virus (VZV)

Answer

Arbovirus

Question 7

What is the most specific diagnostic test for AIDS?

Accepted Answer

Western blot

Answer

Southern blot

Answer

ELISA

Answer

None of the above

Question 8

Human rotaviruses are characterized by which of the following statements?

Accepted Answer

They can be sensitively and rapidly detected in stools by the enzyme-linked immunosorbent assay (ELISA) technique

Answer

They produce an infection that is primarily seen in adults

Answer

They produce cytopathic effects in many conventional tissue culture systems

Answer

They are lipid-containing RNA viruses possessing a double-shelled capsid

Question 9

Which antibodies are used to diagnose acute viral hepatitis A and E?

Accepted Answer

IgM anti-HAV and IgM anti-HEV

Answer

IgG anti-HAV and IgG anti-HEV

Answer

Liver biopsy

Answer

Virus detection in stool

Question 10

All the following viruses are transmitted by arthropod vectors except:

Accepted Answer

Hantavirus

Answer

Dengue

Answer

Chikungunya

Answer

Japanese Encephalitis

Virology — MCQs

Virology — MCQs

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