Virology Practice Questions

Q: A patient has been diagnosed with HBeAg and HBsAg in their serum. What is the most likely condition?

Active and infectious Hepatitis B disease. ### Explanation The presence of **HBsAg** (Hepatitis B surface Antigen) and **HBeAg** (Hepatitis B envelope Antigen) in a patient's serum indicates an **active and highly infectious** state of Hepatitis B virus (HBV) infection. * **HBsAg:** This is the first marker to appear in the blood during infection. Its presence indicates that the virus is currently in the body (either acute or chronic). * **HBeAg:** This is a marker of **active viral replication**. When HBeAg is positive, it signifies a high viral load and high infectivity, meaning the patient is more likely to transmit the virus to others. #### Why other options are incorrect: * **A. Chronic Hepatitis B:** While HBsAg is present in chronic cases (defined as >6 months), the presence of HBeAg specifically highlights the *active/infectious* status. Chronic HBV can be either "HBeAg-positive" (replicative) or "HBeAg-negative" (non-replicative). Without a time frame, "Active and infectious" is the more precise description of the markers provided. * **C. HBV and HBe coinfection:** This is a distractor. HBe is not a separate virus; it is a protein (antigen) produced by the Hepatitis B virus itself. * **D. Recovery from Hepatitis B:** Recovery is characterized by the disappearance of HBsAg and the appearance of **Anti-HBs** (protective antibodies). #### NEET-PG High-Yield Pearls: * **Window Period:** The time when neither HBsAg nor Anti-HBs are detectable. The only marker present is **Anti-HBc IgM**. * **Anti-HBs:** The only marker present after successful **vaccination**. * **HBV DNA:** The most sensitive marker for monitoring viral load and response to antiviral therapy. * **Pre-core Mutants:** Patients who have high HBV DNA but are HBeAg negative (due to a mutation in the pre-core region).

Q: A neonate is born in very poor condition with severe, generalized encephalitis. Which of the following viruses is the most likely pathogen in this setting?

Herpes simplex type II. **Explanation:** The correct answer is **Herpes simplex type II (HSV-2)**. **Why HSV-2 is correct:** Neonatal herpes simplex virus infection is a life-threatening condition typically acquired during delivery through an infected birth canal (vertical transmission). HSV-2 is responsible for approximately 70-80% of neonatal herpes cases. It presents in three patterns: Skin-Eye-Mouth (SEM) disease, Disseminated disease, or **Central Nervous System (CNS) disease**. Neonatal HSV encephalitis causes severe, generalized destruction of brain parenchyma, leading to high mortality and significant neurological sequelae if the infant survives. **Why the other options are incorrect:** * **Eastern Equine Encephalitis (EEE):** While it causes severe encephalitis, it is an arbovirus transmitted via mosquito bites. It is not a classic neonatal pathogen and depends on geographical exposure. * **Herpes Zoster-Varicella Virus (VZV):** Congenital Varicella Syndrome occurs due to maternal infection in early pregnancy (limb hypoplasia, scarring). While neonatal varicella can occur if the mother has active lesions at birth, it typically presents with a disseminated vesicular rash rather than isolated severe encephalitis. * **Poliomyelitis Virus:** Polio is an enterovirus that targets the anterior horn cells of the spinal cord, leading to flaccid paralysis. It does not typically cause generalized encephalitis in neonates. **Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** PCR of the Cerebrospinal Fluid (CSF). * **Treatment:** High-dose intravenous **Acyclovir** is the drug of choice. * **Key Distinction:** In adults, HSV encephalitis is usually caused by **HSV-1** and localized to the **temporal lobes**. In neonates, it is usually **HSV-2** and is **generalized**. * **Prevention:** Cesarean section is indicated if the mother has active genital lesions at the time of labor.

Q: Which one of the following viruses is least likely to cross the placenta?

HBV. **Explanation:** The ability of a virus to cross the placenta depends on its size, the presence of specific receptors on trophoblasts, and the mechanism of transmission. **Why HBV is the correct answer:** Hepatitis B Virus (HBV) is a large DNA virus that **rarely crosses the placenta** during pregnancy. The primary mode of mother-to-child transmission (MTCT) for HBV is **perinatal (vertical)**, occurring during delivery through contact with infected maternal blood or vaginal secretions. Because it does not typically cross the placenta, it is not considered a classic "TORCH" pathogen and does not cause congenital malformations. **Analysis of Incorrect Options:** * **Rubella:** A classic member of the TORCH group. It readily crosses the placenta, especially during the first trimester, leading to **Congenital Rubella Syndrome (CRS)** characterized by cataracts, PDA, and sensorineural deafness. * **Herpes Simplex Virus (HSV):** While most HSV infections are acquired during delivery (neonatal herpes), HSV-2 can cross the placenta (transplacental) in rare cases, leading to skin vesicles, chorioretinitis, and microcephaly. * **HIV:** This virus can cross the placenta at any stage of pregnancy (in utero), though transmission is more common during labor or breastfeeding. Antiretroviral therapy (ART) is used to minimize this risk. **NEET-PG High-Yield Pearls:** * **TORCH Complex:** Toxoplasmosis, Others (Syphilis, Parvovirus B19, VZV), Rubella, CMV, and HSV. Note that HBV is notably absent from this list. * **HBV Management:** To prevent perinatal transmission, the neonate must receive both the **HBV vaccine** and **Hepatitis B Immunoglobulin (HBIG)** within 12 hours of birth. * **HBeAg Status:** The risk of vertical transmission is highest (up to 90%) if the mother is HBeAg positive, indicating high viral replication.

Q: All of the following are transfusion-transmitted viruses except?

Rubella. **Explanation:** The core concept behind transfusion-transmitted infections (TTIs) is that the pathogen must have a significant **viremic phase** in the blood of an asymptomatic carrier. **Why Rubella is the correct answer:** Rubella (German Measles) is primarily a respiratory virus transmitted via **aerosolized droplets**. While a brief transient viremia occurs during the incubation period, the virus does not establish a chronic or latent infection in the blood. Therefore, it is not considered a transfusion-transmitted virus. Its primary clinical significance lies in its teratogenic potential (Congenital Rubella Syndrome), not blood safety. **Analysis of incorrect options:** * **Hepatitis B (HBV):** A classic TTI. It is a DNA virus that persists in the blood of chronic carriers. It is a mandatory screening test (HBsAg) for all blood donations. * **Cytomegalovirus (CMV):** CMV stays latent within **mononuclear leukocytes** (WBCs). It is a major concern in immunocompromised recipients and neonates. Risk is mitigated by using leukoreduced blood products. * **HTLV-1:** Human T-cell Lymphotropic Virus is a retrovirus that infects T-lymphocytes. It is transmitted through blood, sexual contact, and breast milk. Screening is mandatory in many countries to prevent tropical spastic paraparesis and adult T-cell leukemia. **High-Yield Clinical Pearls for NEET-PG:** * **Mandatory screening in India:** HIV 1 & 2, HBV (HBsAg), HCV, Syphilis, and Malaria. * **Most common TTI globally:** Historically Hepatitis B; however, with modern screening, the residual risk is extremely low. * **Window Period:** The time between infection and detection. Nucleic Acid Testing (NAT) is used to reduce this period for HIV, HBV, and HCV. * **Other TTIs to remember:** HIV, HCV, West Nile Virus, Zika virus, and parasites like *Babesia* and *Trypanosoma cruzi*.

Q: In a patient with active chronic hepatitis B, which of the following is NOT typically seen?

IgM anti-HBcAg. ### Explanation The key to answering this question lies in distinguishing between **acute** and **chronic** Hepatitis B virus (HBV) infection based on serological markers [2]. **Why IgM anti-HBcAg is the correct answer:** **IgM anti-HBc (Immunoglobulin M antibody to Hepatitis B core antigen)** is the hallmark of **acute infection** [1]. It appears shortly after HBsAg and is the only marker present during the "window period." In chronic hepatitis B (defined as the persistence of HBsAg for >6 months), the immune response shifts from IgM to **IgG anti-HBc** [2]. Therefore, IgM anti-HBc is typically absent in chronic cases, except during rare, severe acute flares. **Analysis of Incorrect Options:** * **A. HBsAg (Hepatitis B Surface Antigen):** This is the first marker to appear and its persistence for more than 6 months is the defining diagnostic criterion for chronic HBV infection [2]. * **C. HBeAg (Hepatitis B e-Antigen):** This indicates active viral replication and high infectivity. It is commonly seen in the "Immune Tolerant" and "Immune Active" phases of chronic HBV [2]. * **D. Anti-HBsAg:** While usually a sign of recovery or vaccination, low levels of Anti-HBs can coexist with HBsAg in about 10–25% of chronic carriers [2]. These antibodies are unable to neutralize the virus, so their presence does not rule out a chronic state. **NEET-PG High-Yield Pearls:** 1. **Window Period:** The interval where HBsAg disappears but Anti-HBs has not yet appeared. **IgM anti-HBc** is the diagnostic marker here [1]. 2. **Chronic Infection Marker:** **IgG anti-HBc** persists for life in anyone who has had a natural infection (both recovered and chronic) [2]. 3. **Vaccination Marker:** A vaccinated individual will be **Anti-HBs positive** but **Anti-HBc negative** (since the vaccine contains only the surface protein) [2]. 4. **Best indicator of viral replication:** HBV DNA levels (Quantitative PCR) [1].

Q: Which mode of transmission is NOT considered parenteral for hepatitis?

Hepatitis A. **Explanation:** The term **parenteral** refers to routes of transmission other than the alimentary canal (digestive tract), typically involving blood, needles, or direct body fluid contact. **1. Why Hepatitis A is the correct answer:** Hepatitis A virus (HAV) is transmitted via the **fecal-oral route**, primarily through contaminated food and water. It is an enterically transmitted virus. Unlike the other options, it does not cause chronic infection and is not typically spread through blood or blood products. **2. Why the other options are incorrect:** * **Hepatitis B (HBV):** This is the prototype for parenteral transmission. It is spread through blood, needles, sexual contact, and perinatally (vertical transmission). * **Hepatitis C (HCV):** Primarily transmitted through blood-to-blood contact (e.g., IV drug use, blood transfusions before screening). It is the most common cause of post-transfusion hepatitis. * **Hepatitis D (HDV):** As a defective virus that requires the HBsAg coat for replication, its transmission mirrors that of Hepatitis B (parenteral and sexual). **High-Yield NEET-PG Clinical Pearls:** * **Vowels to the Bowels:** Remember that Hepatitis **A** and **E** are transmitted via the fecal-oral route (Enteric). * **Consonants to the Blood:** Hepatitis **B, C, and D** are transmitted parenterally. * **Hepatitis E** is the most common cause of epidemic viral hepatitis in India and is associated with high mortality in **pregnant women** (fulminant hepatic failure). * **Hepatitis C** has the highest risk of progressing to **chronic carrier status** (approx. 75-85%).

Q: Regarding Hepatitis B virus, which of the following statements is true?

HBsAg may be present in saliva.. ### Explanation **Correct Option: D. HBsAg may be present in saliva.** Hepatitis B Virus (HBV) is found in high concentrations in blood, serum, and serous exudates. However, it is also present in moderate concentrations in other body fluids, including **saliva, semen, and vaginal secretions**. While percutaneous (needle-stick) and sexual routes are the primary modes of transmission, the presence of HBsAg in saliva explains why the virus can potentially be transmitted through human bites or close mucosal contact, although it is not typically spread through casual contact like sneezing or coughing. **Analysis of Incorrect Options:** * **A. It is an RNA virus:** HBV is a **DNA virus** belonging to the *Hepadnaviridae* family. It is unique because it possesses a partially double-stranded circular DNA genome and replicates via an RNA intermediate using **reverse transcriptase**. * **B. The incubation period is 2-4 weeks:** The incubation period for HBV is long, typically ranging from **6 weeks to 6 months** (average 60–90 days). A 2–4 week incubation period is more characteristic of Hepatitis A or E. * **C. HBeAg denotes maximum protection:** This is incorrect. **HBeAg (Envelope antigen)** is a marker of **active viral replication and high infectivity**. "Protection" or immunity is denoted by the presence of **Anti-HBs antibodies**. **High-Yield Clinical Pearls for NEET-PG:** * **Window Period:** The interval between the disappearance of HBsAg and the appearance of Anti-HBs. The only marker present during this time is **Anti-HBc IgM**. * **First Marker to appear:** HBsAg (even before symptoms start). * **Indicator of Chronicity:** Persistence of HBsAg for >6 months. * **Dane Particle:** The complete infectious virion (42 nm).

Q: Guarneri bodies are found in which of the following?

Vaccinia. **Explanation:** **1. Why Vaccinia is Correct:** Guarnieri bodies are the characteristic **intracytoplasmic eosinophilic inclusion bodies** found in cells infected with **Variola (Smallpox)** and **Vaccinia** viruses. Since Poxviruses are the only DNA viruses that replicate entirely within the cytoplasm, they create "viral factories" that appear as these distinct inclusions. Identifying these bodies was historically significant for the diagnosis of smallpox. **2. Why the Other Options are Incorrect:** * **Rubella:** This is a Togavirus. While it is an RNA virus that replicates in the cytoplasm, it does not produce classic, named inclusion bodies like Guarnieri bodies. * **Measles:** A Paramyxovirus characterized by **Warthin-Finkeldey giant cells** (multinucleated). It produces both **intracytoplasmic and intranuclear** inclusion bodies (Cowdry type A), but these are not called Guarnieri bodies. * **Mumps:** Another Paramyxovirus. It typically produces eosinophilic intracytoplasmic inclusions, but they are non-specific and lack a specific eponymous name like those in Poxviruses. **3. NEET-PG High-Yield Clinical Pearls:** * **Poxvirus Rule:** All DNA viruses replicate in the nucleus *except* Poxvirus (replicates in cytoplasm). * **Molluscum Contagiosum:** Another Poxvirus that produces large, eosinophilic cytoplasmic inclusions known as **Henderson-Patterson bodies**. * **Cowdry Type A (Intranuclear):** Seen in Herpes Simplex Virus (HSV), Varicella-Zoster Virus (VZV), and Measles. * **Negri Bodies:** Intracytoplasmic inclusions pathognomonic for **Rabies** (found in Hippocampus/Purkinje cells). * **Owl’s Eye Appearance:** Characteristic intranuclear inclusions of **CMV**.

Question 1

Regarding HIV infection, which of the following statements is NOT true?

Accepted Answer

Dendritic cells do not support viral replication.

Answer

p24 antigen is used for early diagnosis.

Answer

Lysis of infected CD4 cells is observed.

Answer

Macrophages serve as a reservoir for the virus.

Question 2

A patient has been diagnosed with HBeAg and HBsAg in their serum. What is the most likely condition?

Accepted Answer

Active and infectious Hepatitis B disease

Answer

Chronic hepatitis B

Answer

HBV and HBe coinfection

Answer

Recovery from Hepatitis B

Question 3

A neonate is born in very poor condition with severe, generalized encephalitis. Which of the following viruses is the most likely pathogen in this setting?

Accepted Answer

Herpes simplex type II

Answer

Eastern equine encephalitis virus

Answer

Herpes zoster-varicella virus

Answer

Poliomyelitis virus

Question 4

Which one of the following viruses is least likely to cross the placenta?

Accepted Answer

HBV

Answer

Rubella

Answer

Herpes Simplex Virus

Answer

HIV

Question 5

All of the following are transfusion-transmitted viruses except?

Accepted Answer

Rubella

Answer

Hepatitis B

Answer

CMV

Answer

HTLV-1

Question 6

In a patient with active chronic hepatitis B, which of the following is NOT typically seen?

Accepted Answer

IgM anti-HBcAg

Answer

HBsAg

Answer

HBeAg

Answer

Anti-HBsAg

Question 7

Which mode of transmission is NOT considered parenteral for hepatitis?

Accepted Answer

Hepatitis A

Answer

Hepatitis B

Answer

Hepatitis C

Answer

Hepatitis D

Question 8

Regarding Hepatitis B virus, which of the following statements is true?

Accepted Answer

HBsAg may be present in saliva.

Answer

It is an RNA virus.

Answer

The incubation period is 2-4 weeks.

Answer

HBeAg denotes maximum protection.

Question 9

Which of the following is a common cause of bronchiolitis in infants?

Accepted Answer

Parainfluenza virus

Answer

Respiratory syncytial virus

Answer

Adenovirus

Answer

Coronavirus

Question 10

Guarneri bodies are found in which of the following?

Accepted Answer

Vaccinia

Answer

Rubella

Answer

Measles

Answer

Mumps

Virology — MCQs

Virology — MCQs

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