Virology — MCQs
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Herpes zoster is caused by which virus?
A 20-year-old woman presents with fever, severe myalgia and arthralgia, pain behind the eyes, and rash for 3 days. Lab reports show thrombocytopenia and leucopenia. What is the most likely diagnosis?
A 48-year-old waitress presents with malaise, loss of appetite, nausea, moderate fever, and jaundice. Laboratory tests indicate a marked increase in serum transaminases. Serology for hepatitis viruses shows positive results for HBsAg, HBc IgM antibody, and HCV antibody. Antibody tests for HBsAb and HAV are negative. What do these results indicate?
In HIV-infected patients, which organism is typically seen on smears from oral lesions?
Which of the following is NOT true about hepatitis E?
Which of the following is NOT increased in HIV infection?
Rotavirus infection is diagnosed by the presence of which of the following?
Congenital varicella zoster infection causes which of the following?
Which of the following methods does not establish the diagnosis of congenital Cytomegalovirus (CMV) infection in a neonate?
The causative organism for AIDS was identified in which year?
Virology Indian Medical PG Practice Questions and MCQs
Question 221: Herpes zoster is caused by which virus?
- A. Herpes simplex type I
- B. Herpes simplex type II
- C. Epstein-Barr virus
- D. Varicella-zoster virus (Correct Answer)
Explanation: **Explanation:** **Varicella-zoster virus (VZV)**, also known as Human Herpesvirus 3 (HHV-3), is the correct answer. VZV causes two distinct clinical entities: 1. **Chickenpox (Varicella):** The primary infection, typically seen in children. 2. **Herpes Zoster (Shingles):** Following the primary infection, the virus remains latent in the **dorsal root ganglia** or cranial nerve ganglia. Reactivation later in life (due to waning immunity or stress) results in Herpes Zoster, characterized by a painful, unilateral vesicular rash restricted to a specific **dermatome**. **Analysis of Incorrect Options:** * **Herpes simplex type I (HSV-1):** Primarily causes orofacial lesions (herpes labialis), gingivostomatitis, and is the most common cause of sporadic fatal encephalitis. * **Herpes simplex type II (HSV-2):** Primarily associated with genital herpes and neonatal herpes; it remains latent in the sacral ganglia. * **Epstein-Barr virus (EBV):** Also known as HHV-4, it causes Infectious Mononucleosis and is associated with malignancies like Burkitt lymphoma and Nasopharyngeal carcinoma. **High-Yield Clinical Pearls for NEET-PG:** * **Tzanck Smear:** A rapid bedside test showing **multinucleated giant cells** with Cowdry type A intranuclear inclusions (seen in VZV, HSV-1, and HSV-2). * **Ramsay Hunt Syndrome:** Reactivation of VZV in the geniculate ganglion involving the facial nerve (CN VII). * **Post-herpetic Neuralgia:** The most common complication of Herpes Zoster. * **Vaccine:** Both live-attenuated and recombinant subunit vaccines are available for prevention.
Question 222: A 20-year-old woman presents with fever, severe myalgia and arthralgia, pain behind the eyes, and rash for 3 days. Lab reports show thrombocytopenia and leucopenia. What is the most likely diagnosis?
- A. Malaria
- B. Dengue fever (Correct Answer)
- C. Typhoid
- D. Yellow fever
Explanation: ### Explanation **Correct Option: B. Dengue fever** The clinical presentation is classic for **Dengue Fever**, often referred to as **"Break-bone fever"** due to the characteristic severe myalgia and arthralgia. The combination of high-grade fever, **retro-orbital pain** (pain behind the eyes), and a maculopapular rash is highly suggestive. Laboratory findings of **thrombocytopenia** (low platelets) and **leucopenia** (low WBC count) are hallmark features of the early phase of Dengue infection caused by the *Flavivirus* (transmitted by the *Aedes aegypti* mosquito). **Why other options are incorrect:** * **A. Malaria:** While it presents with fever and thrombocytopenia, it typically features cyclical paroxysms (chills/rigors) and splenomegaly. Retro-orbital pain and severe arthralgia are not primary features. * **C. Typhoid:** Presents with a "step-ladder" pattern fever, bradycardia (Faget’s sign), and abdominal symptoms. While leucopenia can occur, the severe "break-bone" pains and retro-orbital pain are absent. * **D. Yellow fever:** Though also a *Flavivirus*, it is characterized by jaundice (icterus), hematemesis (black vomit), and Councilman bodies on liver biopsy. It is not endemic in India. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Aedes aegypti* (Day biter; breeds in artificial collections of clean water). * **Serology:** **NS1 Antigen** is the marker of choice for the first 5 days. **IgM ELISA** is used after day 5. * **Tourniquet Test:** A positive test (≥10 petechiae/square inch) indicates capillary fragility. * **Critical Phase:** Occurs during defervescence (when fever drops); this is when plasma leakage and Dengue Shock Syndrome (DSS) are most likely to occur.
Question 223: A 48-year-old waitress presents with malaise, loss of appetite, nausea, moderate fever, and jaundice. Laboratory tests indicate a marked increase in serum transaminases. Serology for hepatitis viruses shows positive results for HBsAg, HBc IgM antibody, and HCV antibody. Antibody tests for HBsAb and HAV are negative. What do these results indicate?
- A. A dual infection of HBV and HAV
- B. Chronic hepatitis A infection
- C. Chronic hepatitis B infection
- D. An acute HBV infection (Correct Answer)
Explanation: ### Explanation The patient presents with classic symptoms of acute hepatitis (jaundice, fever, and elevated transaminases). The diagnosis is confirmed by interpreting the serological markers: 1. **HBsAg (+):** Indicates the presence of Hepatitis B virus (either acute or chronic). 2. **Anti-HBc IgM (+):** This is the **hallmark of acute HBV infection**. IgM antibodies against the core antigen are produced during the initial phase and are the only markers present during the "window period" when HBsAg and HBsAb are both negative. 3. **Anti-HCV (+):** While present, this indicates exposure to Hepatitis C. However, HCV typically causes a chronic, often asymptomatic course rather than the acute, symptomatic presentation described here. 4. **Anti-HAV (-):** Rules out Hepatitis A. **Why other options are incorrect:** * **Option A:** Ruled out because HAV antibodies (IgM) are negative. * **Option B:** Hepatitis A does not have a "chronic" state; it is always an acute, self-limiting infection. * **Option C:** Chronic HBV is characterized by **Anti-HBc IgG**, not IgM. In chronic cases, HBsAg persists for >6 months, and IgM disappears. ### NEET-PG High-Yield Pearls * **Window Period:** The interval between the disappearance of HBsAg and the appearance of HBsAb. **Anti-HBc IgM** is the most reliable marker during this phase. * **Infectivity Marker:** **HBeAg** indicates high viral replication and high infectivity. * **Immunity Marker:** **Anti-HBs (HBsAb)** indicates immunity via recovery or vaccination. * **Vaccination Profile:** A vaccinated individual will be **HBsAb (+)** but **Anti-HBc (-)** (since the vaccine only contains the surface antigen).
Question 224: In HIV-infected patients, which organism is typically seen on smears from oral lesions?
- A. Candida (Correct Answer)
- B. Cryptococcus
- C. Histoplasma
- D. Trichophyton
Explanation: **Explanation:** **1. Why Candida is the Correct Answer:** Oral Candidiasis (Thrush) is the most common opportunistic fungal infection in HIV-infected patients. It typically occurs when the CD4+ T-cell count falls below **200-500 cells/mm³**. The diagnosis is usually clinical, but smears (KOH mount or Gram stain) characteristically show **budding yeast cells and pseudohyphae**. It serves as an important clinical marker for disease progression and is often the first sign of HIV infection. **2. Why the Other Options are Incorrect:** * **B. Cryptococcus:** *Cryptococcus neoformans* primarily causes subacute meningitis or pneumonia in AIDS patients (CD4 <100). While it can rarely cause skin lesions, it is not a typical cause of oral lesions. * **C. Histoplasma:** *Histoplasma capsulatum* causes disseminated disease in immunocompromised hosts, often involving the reticuloendothelial system (liver, spleen, bone marrow). While it can cause oral ulcers, it is far less common than Candida and usually indicates advanced immunosuppression (CD4 <150). * **D. Trichophyton:** This is a dermatophyte responsible for superficial infections of the skin, hair, and nails (e.g., Tinea corporis, Tinea pedis). It does not typically involve the oral mucosa. **3. NEET-PG High-Yield Pearls:** * **Oral Candidiasis Types:** Pseudomembranous (white curd-like patches that **can be scraped off**), Erythematous, and Angular Cheilitis. * **Hairy Leukoplakia:** Another common oral lesion in HIV caused by **EBV**; unlike Candida, it **cannot** be scraped off and appears on the lateral borders of the tongue. * **Treatment:** Topical Nystatin or Clotrimazole for mild cases; oral **Fluconazole** for moderate-to-severe or esophageal involvement. * **Esophageal Candidiasis:** An **AIDS-defining illness** (CD4 <100).
Question 225: Which of the following is NOT true about hepatitis E?
- A. Transmitted by faeco-oral route
- B. Majority of patients develop chronic infection (Correct Answer)
- C. Caused by a non-enveloped, positive-sense, single-stranded RNA genomic, HAV-like virus
- D. Fulminant hepatitis occurs more frequently in pregnancy
Explanation: ### Explanation **Hepatitis E Virus (HEV)** is a major cause of enterically transmitted hepatitis worldwide. Understanding its clinical course and characteristics is vital for NEET-PG. **Why Option B is the Correct Answer (The False Statement):** Hepatitis E is primarily an **acute, self-limiting infection**. Unlike Hepatitis B or C, the majority of immunocompetent patients recover completely and **do not develop chronic infection**. Chronic HEV is rare and seen almost exclusively in immunocompromised individuals (e.g., organ transplant recipients or HIV patients), typically associated with HEV Genotype 3. **Analysis of Incorrect Options:** * **Option A:** HEV is transmitted via the **faeco-oral route**, most commonly through contaminated drinking water. This is similar to Hepatitis A. * **Option C:** HEV is a **non-enveloped**, icosahedral virus with a **positive-sense, single-stranded RNA** genome. It belongs to the *Hepeviridae* family. While it resembles HAV in transmission and structure, it is genetically distinct. * **Option D:** A hallmark of HEV is its high mortality rate (up to 20–25%) in **pregnant women**, particularly during the third trimester, due to **fulminant hepatic failure** and disseminated intravascular coagulation (DIC). --- ### High-Yield Clinical Pearls for NEET-PG: * **Family:** *Hepeviridae* (Genus: *Orthohepevirus*). * **Incubation Period:** 2–9 weeks (Average: 6 weeks). * **Zoonosis:** HEV Genotypes 3 and 4 are zoonotic, often transmitted via undercooked pork or deer meat. * **Diagnosis:** Detection of **IgM anti-HEV** is the gold standard for acute infection. * **Vaccine:** Hecolin (available in China, but not yet globally widespread).
Question 226: Which of the following is NOT increased in HIV infection?
- A. CMV (Correct Answer)
- B. Kaposi sarcoma
- C. Mycobacterial infection
- D. Herpes zoster infection
Explanation: **Explanation:** The question asks which condition is **NOT** increased in frequency due to HIV infection. While HIV leads to profound immunosuppression, the correct answer is **CMV (Cytomegalovirus)** because, in the context of this specific question, CMV is considered a **commensal or ubiquitous virus** that infects a large majority of the general population regardless of HIV status. While CMV **reactivates** and causes severe clinical disease (like retinitis or esophagitis) when CD4 counts drop below 50 cells/mm³, the **seroprevalence (initial infection rate)** is not necessarily higher just because a person has HIV; it is high in the general population due to its mode of transmission. **Analysis of Incorrect Options:** * **Kaposi Sarcoma (KS):** Caused by HHV-8. The risk of developing KS is thousands of times higher in HIV-infected individuals due to the loss of T-cell surveillance. * **Mycobacterial Infection:** HIV is the most potent risk factor for the progression of latent **Tuberculosis** to active disease. Atypical mycobacteria like **MAC** (Mycobacterium avium complex) also increase significantly as CD4 counts decline. * **Herpes Zoster:** Reactivation of the Varicella-Zoster virus (Shingles) occurs much more frequently and with greater severity in HIV-positive patients compared to immunocompetent individuals. **NEET-PG High-Yield Pearls:** * **CD4 < 200:** Risk of *Pneumocystis jirovecii* pneumonia (PCP). * **CD4 < 100:** Risk of Toxoplasmosis and Cryptococcosis. * **CD4 < 50:** Risk of **CMV Retinitis** (presents as "pizza-pie appearance" on fundoscopy) and **MAC**. * **Most common opportunistic infection in HIV (India):** Tuberculosis. * **Most common fungal infection in HIV:** Candidiasis (Oral thrush).
Question 227: Rotavirus infection is diagnosed by the presence of which of the following?
- A. Antigen in stool by ELISA (Correct Answer)
- B. Virus in stool
- C. Antigen in blood
- D. Antibody in stool
Explanation: **Explanation:** Rotavirus is the most common cause of severe, dehydrating diarrhea in infants and young children worldwide. The diagnosis is primarily focused on detecting the virus during the acute phase of the illness. **Why Option A is Correct:** The gold standard for routine clinical diagnosis of Rotavirus is the detection of the **VP6 inner capsid antigen** in the patient's stool. **ELISA (Enzyme-Linked Immunosorbent Assay)** and Latex Agglutination are the most widely used methods because they are rapid, highly sensitive, and cost-effective. Since the virus is shed in massive quantities (up to $10^{12}$ particles per gram of stool), antigen detection is highly reliable. **Analysis of Incorrect Options:** * **B. Virus in stool:** While the virus is present in the stool, visualizing the actual virus requires **Electron Microscopy (EM)**. EM shows the characteristic "wheel-like" appearance (Latin: *Rota*), but it is labor-intensive and not used for routine diagnosis. * **C. Antigen in blood:** Rotavirus is a localized infection of the mature enterocytes of the small intestine. It does not typically cause significant viremia; therefore, blood antigen tests are not used for diagnosis. * **D. Antibody in stool:** While local IgA is produced, testing for antibodies in stool is not a standardized or practical diagnostic approach compared to antigen detection. **High-Yield NEET-PG Pearls:** * **Morphology:** Reoviridae family; Double-stranded RNA (dsRNA) with **11 segments**. * **Appearance:** "Cartwheel" appearance on Electron Microscopy. * **Pathogenesis:** Produces an enterotoxin called **NSP4**, which induces secretory diarrhea. * **Vaccines:** Live attenuated oral vaccines (Rotarix, RotaTeq, and the indigenous Rotavac) are part of the National Immunization Schedule in India.
Question 228: Congenital varicella zoster infection causes which of the following?
- A. Microcephaly
- B. Limb hypoplasia
- C. IUGR
- D. All of the above (Correct Answer)
Explanation: **Explanation:** Congenital Varicella Syndrome (CVS) occurs when a pregnant woman contracts primary Varicella Zoster Virus (VZV) infection, typically between the **8th and 20th weeks of gestation**. The virus crosses the placenta and establishes a latent infection in the fetal sensory ganglia, subsequently reactivating in utero to cause multi-organ damage. The correct answer is **D (All of the above)** because CVS is characterized by a classic triad of clinical features: 1. **Cutaneous lesions:** Cicatricial (zigzag) skin scarring in a dermatomal distribution. 2. **Neurological defects:** This includes **Microcephaly**, cortical atrophy, and mental retardation. 3. **Limb abnormalities:** **Limb hypoplasia** (underdeveloped limbs) is a hallmark sign, often accompanied by rudimentary digits and talipes equinovarus. 4. **Ocular and Growth defects:** Chorioretinitis, cataracts, and **Intrauterine Growth Restriction (IUGR)** are frequently observed due to the systemic nature of the viral insult. **Why other options are included:** Options A, B, and C are all individual components of the syndrome. Selecting only one would be incomplete, as VZV is a potent teratogen affecting the central nervous system, musculoskeletal system, and overall fetal development simultaneously. **High-Yield Clinical Pearls for NEET-PG:** * **Risk Period:** Highest risk is during the first 20 weeks (approx. 2% risk). Infection after 20 weeks rarely causes CVS. * **Neonatal Varicella:** If the mother develops a rash 5 days before to 2 days after delivery, the neonate is at risk of life-threatening disseminated varicella (not CVS). * **Prophylaxis:** Exposed susceptible pregnant women should receive **Varicella-Zoster Immunoglobulin (VZIG)** within 10 days of exposure to prevent maternal and fetal complications. * **Diagnosis:** Prenatal diagnosis can be made via ultrasound (detecting limb deformities) or PCR of amniotic fluid.
Question 229: Which of the following methods does not establish the diagnosis of congenital Cytomegalovirus (CMV) infection in a neonate?
- A. Urine culture positive for CMV
- B. Presence of IgG CMV antibodies in blood (Correct Answer)
- C. Intra-nuclear inclusion bodies in hepatocytes
- D. Detection of CMV viral DNA in blood by polymerase chain reaction
Explanation: **Explanation:** To diagnose **congenital** Cytomegalovirus (CMV) infection, the virus or its components must be detected within the **first 2–3 weeks of life**. After this period, a positive result may represent perinatally acquired infection rather than congenital. **Why Option B is the Correct Answer:** The presence of **IgG antibodies** in a neonate’s blood is not diagnostic of congenital infection because IgG crosses the placenta from the mother to the fetus (passive immunity). Therefore, a positive IgG test in a newborn simply reflects maternal past infection or immunity, not necessarily an active infection in the infant. To diagnose congenital CMV via serology, one must detect **CMV-specific IgM** (which does not cross the placenta) or observe a persistent/rising IgG titer over several months. **Analysis of Incorrect Options:** * **Option A (Urine Culture):** This is the traditional **"Gold Standard."** CMV is shed in high titers in the urine of infected neonates. * **Option C (Inclusion Bodies):** Histopathology showing characteristic **"Owl’s eye"** intranuclear inclusion bodies in tissues (like hepatocytes or renal tubular cells) is a definitive sign of active CMV infection. * **Option D (PCR):** Detection of CMV DNA in blood, urine, or saliva via PCR is currently the most sensitive and preferred rapid diagnostic method. **NEET-PG High-Yield Pearls:** * **Most common** cause of congenital malformation and sensorineural hearing loss (SNHL) in the developed world. * **Classic Triad:** Chorioretinitis, Hydrocephalus, and Intracranial calcifications (Note: CMV calcifications are typically **periventricular**, whereas Toxoplasmosis calcifications are diffuse). * **Best Sample for Screening:** Saliva PCR (confirmed by urine PCR). * **Treatment of choice:** Ganciclovir or Valganciclovir.
Question 230: The causative organism for AIDS was identified in which year?
- A. 1983 (Correct Answer)
- B. 1976
- C. 1994
- D. 1969
Explanation: **Explanation:** The causative agent of AIDS, now known as Human Immunodeficiency Virus (HIV), was first isolated and identified in **1983**. This breakthrough was achieved by **Luc Montagnier** and his team at the Pasteur Institute in France, who initially named the virus **LAV** (Lymphadenopathy-Associated Virus). Simultaneously, Robert Gallo’s team in the USA identified it as **HTLV-III**. The term HIV was later standardized in 1986. **Analysis of Options:** * **1983 (Correct):** This marks the definitive identification of the virus. The first clinical reports of the disease (then called "GRID") appeared slightly earlier in 1981. * **1976 (Incorrect):** This year is significant for the first recognized outbreak of the **Ebola virus** in Zaire and Sudan, not HIV. * **1994 (Incorrect):** By this time, HIV research was advanced; 1994 is notable for the landmark **ACTG 076 trial**, which proved that Zidovudine (AZT) could prevent mother-to-child transmission. * **1969 (Incorrect):** While retrospective studies suggest HIV may have been circulating in humans earlier, it was completely unknown to science in 1969. **High-Yield Clinical Pearls for NEET-PG:** * **Family:** Retroviridae; **Genus:** Lentivirus. * **Primary Receptor:** CD4 molecule (found on T-helper cells, macrophages, and dendritic cells). * **Co-receptors:** **CCR5** (predominant in early infection/macrophages) and **CXCR4** (late infection/T-cells). * **Screening Test:** ELISA (High sensitivity). * **Confirmatory Test:** Western Blot (detects antibodies to p24, gp41, and gp120/160). *Note: Newer algorithms prefer Fourth Generation Immunoassays.* * **Monitoring:** Viral load (RT-PCR) is the best predictor of disease progression.
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Virus Structure and Classification
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Viral Replication
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Pathogenesis of Viral Infections
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DNA Viruses: Herpesviruses
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DNA Viruses: Poxviruses and Adenoviruses
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Hepatitis Viruses
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RNA Viruses: Orthomyxoviruses
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RNA Viruses: Paramyxoviruses
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Arboviruses
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HIV and Retroviruses
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Oncogenic Viruses
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