Virology Practice Questions

Q: Which of the following is NOT a route of transmission for rabies?

Ingestion. **Explanation:** Rabies is a fatal zoonotic viral disease caused by the **Lyssavirus** (Rhabdoviridae family). The virus is highly neurotropic and is primarily transmitted through the inoculation of infected saliva into the body. **Why Ingestion is the Correct Answer:** The Rabies virus is extremely labile and is easily destroyed by gastric acid and digestive enzymes. Therefore, **ingestion** of contaminated food or milk is not a recognized route of transmission in humans. Even if an animal consumes the meat of a rabid carcass, infection does not occur via the gastrointestinal tract unless there are pre-existing lacerations in the oral mucosa. **Analysis of Other Options:** * **Bite (Option A):** This is the most common route (>99% of cases). The virus is present in the saliva of the rabid animal and enters the host through the broken skin. * **Lick (Option B):** Transmission can occur if a rabid animal licks **pre-existing wounds, scratches, or intact mucous membranes** (eyes, mouth). This is classified as a Category II or III exposure depending on the severity. * **Aerosol (Option C):** Though rare, aerosolized transmission has been documented in laboratory accidents and among individuals exploring caves inhabited by millions of infected bats (due to high concentrations of viral particles in the air). **High-Yield Clinical Pearls for NEET-PG:** * **Incubation Period:** Usually 1–3 months; depends on the distance of the bite from the CNS. * **Pathognomonic Feature:** **Negri bodies** (intracytoplasmic eosinophilic inclusions) found in the hippocampus and cerebellum. * **Organ Transplant:** Rabies can be transmitted via **corneal or solid organ transplants** from infected donors. * **Post-Exposure Prophylaxis (PEP):** Includes wound washing, Rabies Vaccine (IDRV/IM), and Rabies Immunoglobulin (RIG) for Category III bites.

Q: Which of the following infections has the highest chance of transmission by blood transfusion?

HBV. **Explanation:** The risk of transfusion-transmitted infections (TTI) is determined by the prevalence of the virus in the donor population, the duration of the "window period," and the sensitivity of screening methods. **Why HBV is the Correct Answer:** Hepatitis B Virus (HBV) remains the most common transfusion-transmitted viral infection worldwide. The primary reason is the **long window period** (averaging 30–60 days) and the presence of **Occult HBV Infection (OBI)**. In OBI, individuals are HBsAg negative but possess HBV DNA in their blood. Even with Nucleic Acid Testing (NAT), the low viral load in occult cases can sometimes escape detection, leading to a higher transmission rate compared to other viruses. **Analysis of Incorrect Options:** * **HIV (Option A):** While highly feared, the transmission risk is significantly lower than HBV due to a shorter window period (especially with NAT) and lower prevalence among voluntary donors. * **HTLV-1 (Option C):** Human T-cell Lymphotropic Virus has a very low prevalence in the general population compared to Hepatitis viruses, making it a rare cause of TTI. * **HCV (Option D):** Hepatitis C previously had a high transmission rate, but the introduction of highly sensitive NAT has reduced the window period to approximately 3–5 days, making its transmission risk lower than HBV. **NEET-PG High-Yield Pearls:** * **Order of Transmission Risk:** HBV > HCV > HIV. * **Most common infection transmitted by blood transfusion:** HBV. * **Most common cause of Post-Transfusion Hepatitis (PTH):** Historically HCV, but currently, HBV is more frequent in many developing regions due to OBI. * **Window Period:** The time between infection and the point when a laboratory test can detect the antigen/antibody. * **Screening:** Mandatory screening in India includes HIV 1&2, HBV (HBsAg), HCV, Syphilis, and Malaria.

Q: A viral organism was isolated from a painful blister on the lip of a girl. The agent was found to have double-stranded, linear DNA and was enveloped. What is the most likely causative organism?

Herpes simplex virus (HSV). ### Explanation **Correct Option: B. Herpes simplex virus (HSV)** The clinical presentation of a **painful blister on the lip** is classic for **Herpes Labialis** (cold sores), most commonly caused by **HSV-1**. From a virological perspective, HSV belongs to the *Herpesviridae* family, which is characterized by a **double-stranded, linear DNA** genome, an icosahedral capsid, and a lipid **envelope** derived from the host nuclear membrane. **Analysis of Incorrect Options:** * **A. Epstein-Barr virus (EBV):** While EBV is a herpesvirus (DS DNA, enveloped), it typically causes Infectious Mononucleosis (fever, pharyngitis, lymphadenopathy) or Burkitt lymphoma, not localized painful vesicles on the lip. * **C. Cytomegalovirus (CMV):** Also a herpesvirus, but it usually presents as a mononucleosis-like syndrome or opportunistic infections in immunocompromised patients (e.g., retinitis). It does not cause labial blisters. * **D. Poxvirus:** Although Poxviruses (like Molluscum contagiosum or Variola) have DS DNA and an envelope, their DNA is **complex/brick-shaped** rather than simple icosahedral, and they replicate in the **cytoplasm** (unlike other DNA viruses). Clinically, they do not present as typical herpetic vesicles. **NEET-PG High-Yield Pearls:** * **Tzanck Smear:** Look for **Multinucleated Giant Cells** and **Cowdry Type A** intranuclear inclusion bodies in HSV lesions. * **Latency:** HSV-1 remains latent in the **Trigeminal ganglion**, while HSV-2 remains latent in the **Sacral ganglion**. * **Enveloping:** Herpesviruses are unique because they acquire their envelope by budding through the **inner nuclear membrane** of the host cell. * **Drug of Choice:** Acyclovir (inhibits viral DNA polymerase).

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.

Question 1

Which of the following is NOT a route of transmission for rabies?

Accepted Answer

Ingestion

Answer

Bite

Answer

Lick

Answer

Aerosol

Question 2

Which of the following infections has the highest chance of transmission by blood transfusion?

Accepted Answer

HBV

Answer

HIV

Answer

HTLV-1

Answer

HCV

Question 3

A viral organism was isolated from a painful blister on the lip of a girl. The agent was found to have double-stranded, linear DNA and was enveloped. What is the most likely causative organism?

Accepted Answer

Herpes simplex virus (HSV)

Answer

Epstein-Barr virus (EBV)

Answer

Cytomegalovirus (CMV)

Answer

Poxvirus

Question 4

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 5

Pharyngoconjunctival fever is caused by which of the following viruses?

Accepted Answer

Adenovirus

Answer

Parainfluenza virus

Answer

Haemophilus influenza

Answer

Coxsackie virus

Question 6

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 7

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 8

Which of the following is NOT increased in HIV infection?

Accepted Answer

CMV

Answer

Kaposi sarcoma

Answer

Mycobacterial infection

Answer

Herpes zoster infection

Question 9

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 10

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)

Virology — MCQs

Virology — MCQs

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