Virology Practice Questions

Q: Hepatitis A virus (HAV) is not destroyed by:

0.5 ppm chlorine. **Explanation:** Hepatitis A Virus (HAV) is a non-enveloped, single-stranded RNA virus belonging to the *Picornaviridae* family. Its lack of a lipid envelope makes it exceptionally hardy and resistant to many common environmental stressors and disinfectants. **1. Why 0.5 ppm Chlorine is the correct answer:** HAV is notably resistant to low concentrations of chlorine. While standard water chlorination is effective against many bacteria, HAV requires higher concentrations for complete inactivation. It is inactivated by **free residual chlorine at 1.0 to 1.5 ppm** (parts per million). Therefore, a concentration of 0.5 ppm is insufficient to destroy the virus. **2. Analysis of Incorrect Options:** * **1:4000 Formalin:** HAV is inactivated by treatment with formalin (1:4000) at 37°C for 72 hours. This method is historically significant in the production of inactivated HAV vaccines. * **UV Radiation:** Like most viruses, HAV is susceptible to ultraviolet radiation, which damages its RNA genome, rendering it non-infectious. * **Boiling at 100°C for 5 minutes:** HAV is relatively heat-stable (withstanding 60°C for an hour), but it is reliably inactivated by high heat. Boiling at 100°C for 5 minutes (or even 1 minute) is sufficient to destroy the virus. **Clinical Pearls for NEET-PG:** * **Transmission:** Primarily Feco-oral route. * **Stability:** HAV remains stable at low pH (pH 1), allowing it to survive the gastric acid barrier. * **Disinfection:** To effectively kill HAV on surfaces, a 1:100 dilution of sodium hypochlorite (household bleach) is typically recommended. * **Diagnosis:** The presence of **IgM anti-HAV** is the gold standard for diagnosing acute infection. * **Vaccination:** It is a killed vaccine, usually given in two doses (0 and 6–12 months).

Q: Pharyngoconjunctival fever is caused by which of the following viruses?

Adenovirus. **Explanation:** **Pharyngoconjunctival Fever (PCF)** is a specific clinical syndrome caused by **Adenovirus**, most commonly **serotypes 3, 4, and 7**. It typically presents as a triad of: 1. **Follicular conjunctivitis** (usually non-purulent) 2. **Pharyngitis** (sore throat) 3. **Fever** The infection is highly contagious, often spreading through respiratory droplets or contaminated water in swimming pools (hence the name "Swimming Pool Conjunctivitis"). It is usually self-limiting, lasting 7–14 days. **Analysis of Incorrect Options:** * **Parainfluenza virus:** Primarily causes respiratory infections like Croup (laryngotracheobronchitis) in children, not a specific conjunctivitis syndrome. * **Haemophilus influenzae:** This is a bacterium, not a virus. While it can cause bacterial conjunctivitis (especially in children), it does not cause the viral follicular pattern seen in PCF. * **Coxsackie virus:** Specifically Coxsackie A24 (and Enterovirus 70) are the primary causes of **Acute Hemorrhagic Conjunctivitis (AHC)**, characterized by subconjunctival hemorrhages, rather than the pharyngitis-fever triad. **High-Yield Clinical Pearls for NEET-PG:** * **Epidemic Keratoconjunctivitis (EKC):** Also caused by Adenovirus (Serotypes **8, 19, 37**). Unlike PCF, EKC is more severe, lacks systemic symptoms (no fever/sore throat), and is notorious for causing **subepithelial corneal infiltrates**. * **Transmission:** Adenovirus is resistant to many common disinfectants; handwashing and instrument sterilization (tonometers) are crucial to prevent outbreaks. * **Management:** Treatment is primarily supportive (cold compresses and artificial tears) as it is a self-limiting viral condition.

Q: 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?

An acute HBV infection. ### 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).

Q: Which of the following is NOT true about hepatitis E?

Majority of patients develop chronic infection. ### 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).

Q: Which of the following is NOT increased in HIV infection?

CMV. **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).

Q: A 30-year-old male presented with complaints of sudden onset of fever, chills, severe headache, backache, and retro-orbital pain for 3 days. On the 3rd day, a rash appeared on the face, thorax, and flexor surfaces. The rash was macular and confluent. The tourniquet test was positive. Lab findings revealed a low platelet count, low WBC count, increased SGOT and SGPT levels, and a hematocrit increase by >20%. The above disease is transmitted by which of the following vectors?

Aedes aegypti mosquito. ### Explanation **Diagnosis: Dengue Fever (Dengue Hemorrhagic Fever)** The clinical presentation of sudden onset high-grade fever, severe headache, retro-orbital pain (classic "break-bone fever"), and a confluent macular rash is characteristic of Dengue [1]. The laboratory findings of **thrombocytopenia** (low platelets), **leukopenia** (low WBC), and **elevated transaminases** (SGOT/SGPT) further support this. Crucially, a **positive tourniquet test** and a **hematocrit increase of >20%** (indicating plasma leakage) satisfy the WHO criteria for **Dengue Hemorrhagic Fever (DHF)** [1]. **Why the Correct Answer is Right:** * **Aedes aegypti mosquito:** This is the primary vector for the Dengue virus (a Flavivirus). It is a day-biting mosquito that typically breeds in stagnant clean water (e.g., flower pots, coolers). While *Aedes albopictus* can also transmit the virus, *Aedes aegypti* is the most efficient and common urban vector. **Why Other Options are Wrong:** * **Anopheles mosquito:** The primary vector for **Malaria**. It typically bites at night and does not present with the "rash and retro-orbital pain" triad seen here. * **Aedes mosquito:** While technically correct, it is less specific than "Aedes aegypti." In NEET-PG, if a specific species is provided alongside a genus, the specific species is the preferred answer. * **Culex mosquito:** The vector for **Japanese Encephalitis, West Nile Virus, and Bancroftian Filariasis**. **NEET-PG Clinical Pearls:** * **Herman’s Rash:** The classic Dengue rash is described as "islands of white in a sea of red." * **Critical Phase:** Occurs during defervescence (days 3–7), where plasma leakage leads to pleural effusion, ascites, and hemoconcentration [1]. * **NS1 Antigen:** The most reliable marker for early diagnosis (Days 1–5). * **Aedes aegypti** also transmits: Zika virus, Chikungunya, and Yellow Fever.

Q: What are the primary hosts in the natural life cycle of the Japanese Encephalitis (JE) virus?

Pigs and Mosquitoes. ### Explanation Japanese Encephalitis (JE) is a zoonotic viral infection caused by a **Flavivirus**. Understanding its transmission cycle is crucial for NEET-PG, as it involves distinct roles for different species. **Why Option A is Correct:** The natural life cycle of the JE virus is maintained primarily between **Pigs** and **Mosquitoes** (specifically the *Culex tritaeniorhynchus* group). * **Pigs** act as the **amplifier hosts**; they develop high-titer viremia without getting sick, allowing mosquitoes to pick up the virus easily. * **Mosquitoes** are the **vectors** that transmit the virus between hosts. * **Ardeid birds** (herons, egrets) also serve as natural reservoirs, but the pig-mosquito cycle is the primary driver of human outbreaks. **Analysis of Incorrect Options:** * **B (Cattle and Birds):** While birds are reservoirs, cattle are "dead-end" hosts. They may develop antibodies but do not produce enough viremia to infect mosquitoes. * **C (Pigs and Humans):** Humans are **accidental, dead-end hosts**. The level of viremia in humans is transient and insufficient to infect a biting mosquito; therefore, human-to-mosquito-to-human transmission does not occur. * **D (Birds and Pigs):** While both are vertebrate hosts, this option excludes the **Mosquito**, which is a "primary host" (biological vector) essential for the virus's life cycle and transmission. **High-Yield Clinical Pearls for NEET-PG:** 1. **Vector:** *Culex tritaeniorhynchus* (breeds in stagnant water/paddy fields; "outdoor" biters). 2. **Amplifier Host:** Pig (The "Link" between nature and humans). 3. **Dead-end Hosts:** Humans and Horses. 4. **Sentinel Animals:** Pigs are used for surveillance to monitor the presence of the virus in a community. 5. **Vaccination:** Live attenuated (SA-14-14-2) and Inactivated vaccines are available under the Universal Immunization Programme (UIP) in endemic districts.

Q: Reassortment has enabled the development of live vaccines, which is a feature of the following virus?

Rotavirus. ### Explanation The correct answer is **Rotavirus**. **Why Rotavirus is correct:** The underlying concept here is **Genetic Reassortment**, which occurs only in viruses with **segmented genomes**. When two different strains of a segmented virus infect the same cell, they can exchange entire gene segments during assembly, creating a new progeny with a novel genetic mix. Rotavirus belongs to the *Reoviridae* family and possesses a genome of **11 segments of double-stranded RNA (dsRNA)**. This feature was exploited to develop live-attenuated vaccines like the **RotaTeq (RV5)** vaccine, which is a pentavalent human-bovine reassortant vaccine. **Why the other options are incorrect:** * **Hepadnavirus (e.g., Hepatitis B):** These are DNA viruses with a partially double-stranded circular genome. They do not have segments and thus cannot undergo reassortment. * **Herpesvirus:** These are large, enveloped viruses with a single, continuous piece of linear double-stranded DNA. They undergo recombination but not reassortment. * **Astrovirus:** These are small, non-enveloped viruses with a single-stranded, positive-sense RNA genome (ssRNA+). Since the genome is non-segmented, reassortment is impossible. **High-Yield Clinical Pearls for NEET-PG:** * **Segmented Viruses Mnemonic:** **BOAR** (**B**unyavirus - 3 segments, **O**rthomyxovirus/Influenza - 8 segments, **A**renavirus - 2 segments, **R**eovirus/Rotavirus - 11 segments). * **Antigenic Shift:** Reassortment is the mechanism behind "Antigenic Shift" in Influenza A, leading to pandemics. * **Rotavirus Vaccine:** Note that **Rotarix** is a monovalent human attenuated vaccine, while **RotaTeq** is the reassortant one. * **Clinical Presentation:** Rotavirus is the most common cause of severe diarrhea in infants and young children worldwide ("Winter diarrhea").

Q: Which virus is documented to cause fetal damage?

Varicella. **Explanation:** The correct answer is **Varicella (B)**. **Why Varicella is correct:** Varicella-Zoster Virus (VZV) is a well-documented teratogen. When a pregnant woman contracts primary varicella (chickenpox) during the first 20 weeks of gestation, the virus can cross the placenta and cause **Congenital Varicella Syndrome**. This syndrome is characterized by skin scarring (cicatricial lesions in a dermatomal distribution), limb hypoplasia, microcephaly, chorioretinitis, and cataracts. **Why the other options are incorrect:** * **Hepatitis A (A):** This is an enterically transmitted virus (fecal-oral). While it can cause acute hepatitis in the mother, it is not associated with congenital malformations or direct fetal damage. * **Measles (C):** While measles infection during pregnancy is associated with adverse outcomes like spontaneous abortion, premature labor, and low birth weight, it is **not** documented to be teratogenic (it does not cause structural fetal malformations). * **Arbovirus (D):** Most arboviruses (like Dengue or West Nile) do not typically cause fetal damage. *Note:* While Zika virus (an arbovirus) is a known teratogen, it is not the standard answer in this classic MCQ context compared to the established risk of Varicella. **NEET-PG High-Yield Pearls:** * **Congenital Rubella Syndrome (CRS):** The most common viral cause of fetal damage (Classic triad: Cataract, Deafness, Cardiac defects like PDA). * **Cytomegalovirus (CMV):** The most common *infectious* cause of sensorineural hearing loss and mental retardation in neonates. * **Varicella Prophylaxis:** If a susceptible pregnant woman is exposed to VZV, **Varicella-Zoster Immunoglobulin (VZIG)** should be administered within 96 hours to prevent maternal and fetal complications.

Question 1

Hepatitis A virus (HAV) is not destroyed by:

Accepted Answer

0.5 ppm chlorine

Answer

1:4000 formalin

Answer

UV radiation

Answer

Boiling at 100°C for 5 minutes

Question 2

Pharyngoconjunctival fever is caused by which of the following viruses?

Accepted Answer

Adenovirus

Answer

Parainfluenza virus

Answer

Haemophilus influenza

Answer

Coxsackie virus

Question 3

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?

Accepted Answer

An acute HBV infection

Answer

A dual infection of HBV and HAV

Answer

Chronic hepatitis A infection

Answer

Chronic hepatitis B infection

Question 4

Which of the following is NOT true about hepatitis E?

Accepted Answer

Majority of patients develop chronic infection

Answer

Transmitted by faeco-oral route

Answer

Caused by a non-enveloped, positive-sense, single-stranded RNA genomic, HAV-like virus

Answer

Fulminant hepatitis occurs more frequently in pregnancy

Question 5

Which of the following is NOT increased in HIV infection?

Accepted Answer

CMV

Answer

Kaposi sarcoma

Answer

Mycobacterial infection

Answer

Herpes zoster infection

Question 6

A 30-year-old male presented with complaints of sudden onset of fever, chills, severe headache, backache, and retro-orbital pain for 3 days. On the 3rd day, a rash appeared on the face, thorax, and flexor surfaces. The rash was macular and confluent. The tourniquet test was positive. Lab findings revealed a low platelet count, low WBC count, increased SGOT and SGPT levels, and a hematocrit increase by >20%. The above disease is transmitted by which of the following vectors?

Accepted Answer

Aedes aegypti mosquito

Answer

Anopheles mosquito

Answer

Aedes mosquito

Answer

Culex mosquito

Question 7

Which of the following viruses belongs to the family Herpesviridae?

Accepted Answer

Reovirus (RK virus is likely a typo and should refer to Reovirus, which can cause a range of infections)

Answer

Variola virus

Answer

Adenovirus

Answer

Human Papillomavirus (HPV)

Question 8

What are the primary hosts in the natural life cycle of the Japanese Encephalitis (JE) virus?

Accepted Answer

Pigs and Mosquitoes

Answer

Cattle and Birds

Answer

Pigs and Humans

Answer

Birds and Pigs

Question 9

Reassortment has enabled the development of live vaccines, which is a feature of the following virus?

Accepted Answer

Rotavirus

Answer

Hepadnavirus

Answer

Herpesvirus

Answer

Astrovirus

Question 10

Which virus is documented to cause fetal damage?

Accepted Answer

Varicella

Answer

Hepatitis A

Answer

Measles

Answer

Arbovirus

Virology — MCQs

Virology — MCQs

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