Virology Practice Questions

Q: Which virus is responsible for non-immune hydrops fetalis?

Parvovirus. **Explanation:** **Parvovirus B19** is the most common viral cause of **non-immune hydrops fetalis**. The virus specifically targets and infects **erythroid progenitor cells** (via the P-antigen receptor), leading to a temporary cessation of red blood cell production. In a fetus, who has a high rate of erythrocyte turnover and an expanding blood volume, this results in **severe fetal anemia**. The resulting high-output cardiac failure leads to generalized edema (anasarca), pleural/pericardial effusions, and ascites—collectively known as hydrops fetalis. **Analysis of Incorrect Options:** * **A. Cytomegalovirus (CMV):** While CMV is the most common congenital infection, it typically presents with periventricular calcifications, microcephaly, and sensorineural hearing loss rather than hydrops. * **B. Herpes Simplex Virus (HSV):** Neonatal HSV is usually acquired during delivery (birth canal) and presents as skin-eye-mouth (SEM) lesions, encephalitis, or disseminated disease, but not typically as hydrops. * **C. Hepatitis B Virus (HBV):** HBV is transmitted vertically but is not teratogenic and does not cause fetal structural anomalies or hydrops; it primarily leads to chronic carrier status in the neonate. **High-Yield Clinical Pearls for NEET-PG:** * **Fifth Disease:** Parvovirus B19 causes Erythema Infectiosum ("Slapped cheek" appearance) in children. * **Aplastic Crisis:** It can cause transient aplastic crisis in patients with underlying hemolytic anemias (e.g., Sickle Cell, Spherocytosis). * **Diagnosis:** Fetal hydrops is diagnosed via ultrasound; maternal infection is confirmed via IgM antibodies or PCR. * **Management:** Intrauterine blood transfusion (IUT) can be life-saving for the hydropic fetus.

Q: Which of the following is NOT an oncogenic virus?

Herpes simplex virus. **Explanation:** The correct answer is **Herpes simplex virus (HSV)**. While many members of the Herpesviridae family are associated with malignancy, HSV-1 and HSV-2 are primarily associated with acute and recurrent mucosal infections (cold sores and genital herpes) and have **not** been proven to be oncogenic in humans. **Why the other options are incorrect (Oncogenic Viruses):** * **Human Papillomavirus (HPV):** High-risk types (16, 18) are the primary cause of cervical, anogenital, and oropharyngeal cancers. They produce E6 and E7 oncoproteins which inhibit tumor suppressors p53 and pRb, respectively. * **Epstein-Barr Virus (EBV):** A potent oncogenic virus associated with Burkitt lymphoma, Nasopharyngeal carcinoma, Hodgkin lymphoma, and Post-transplant lymphoproliferative disorder (PTLD). * **Hepatitis B Virus (HBV):** A DNA virus that causes chronic inflammation and integrates into the host genome (via the HBx protein), significantly increasing the risk of Hepatocellular Carcinoma (HCC). **High-Yield Clinical Pearls for NEET-PG:** * **RNA Oncogenic Viruses:** Human T-cell Lymphotropic Virus-1 (HTLV-1) and Hepatitis C Virus (HCV) are the key RNA viruses linked to cancer. * **HHV-8:** Also known as Kaposi Sarcoma-associated Herpesvirus (KSHV), it is the herpesvirus most strongly linked to malignancy (Kaposi sarcoma and Primary effusion lymphoma). * **Mechanism:** Most DNA oncogenic viruses act by neutralizing host "gatekeeper" proteins like **p53** and **pRb**.

Q: A child presents with mononucleosis-like symptoms, but the test for mononucleosis and EBV titers are negative. What is a common cause of heterophile-negative mononucleosis?

Cytomegalovirus. ### Explanation **Correct Answer: A. Cytomegalovirus (CMV)** **Why it is correct:** Infectious Mononucleosis (IM) is most commonly caused by the Epstein-Barr Virus (EBV). However, approximately 10% of mononucleosis-like syndromes are **heterophile-negative**, meaning the Monospot test (which detects IgM antibodies that agglutinate horse/sheep RBCs) is negative. **Cytomegalovirus (CMV)** is the most common cause of heterophile-negative mononucleosis. While clinical features like fever and atypical lymphocytosis are similar to EBV, CMV mononucleosis typically presents with **milder pharyngitis** and **less prominent lymphadenopathy or splenomegaly.** **Why the other options are incorrect:** * **B. Herpes simplex virus (HSV):** Primarily causes gingivostomatitis, herpes labialis, or encephalitis; it does not typically present with a mononucleosis-like syndrome or atypical lymphocytosis. * **C. Varicella-zoster virus (VZV):** Causes chickenpox and shingles, characterized by a distinct vesicular rash in different stages of evolution. * **D. Adenovirus:** While it can cause pharyngitis and conjunctivitis (pharyngoconjunctival fever), it does not produce the systemic atypical lymphocytosis characteristic of mononucleosis. **High-Yield Clinical Pearls for NEET-PG:** * **The "Big Three" of Heterophile-Negative IM:** 1. CMV (Most common), 2. Acute HIV infection, 3. Toxoplasmosis. * **Diagnostic Hallmark:** Look for "Owl’s eye" intranuclear inclusion bodies in biopsy (though diagnosis is usually serological or via PCR). * **Drug Reaction:** Like EBV, giving **Ampicillin/Amoxicillin** in CMV mononucleosis can trigger a maculopapular skin rash. * **Atypical Lymphocytes:** These are actually **activated T-cells (CD8+)** reacting against the B-cells infected by the virus.

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%).

Question 1

Which virus is responsible for non-immune hydrops fetalis?

Accepted Answer

Parvovirus

Answer

Cytomegalovirus

Answer

Herpes simplex virus

Answer

Hepatitis B virus

Question 2

Which of the following is NOT an oncogenic virus?

Accepted Answer

Herpes simplex virus

Answer

Human papilloma virus

Answer

Epstein-Barr virus

Answer

Hepatitis B virus

Question 3

A child presents with mononucleosis-like symptoms, but the test for mononucleosis and EBV titers are negative. What is a common cause of heterophile-negative mononucleosis?

Accepted Answer

Cytomegalovirus

Answer

Herpes simplex virus

Answer

Varicella-zoster virus

Answer

Adenovirus

Question 4

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 5

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 6

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 7

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 8

All of the following are transfusion-transmitted viruses except?

Accepted Answer

Rubella

Answer

Hepatitis B

Answer

CMV

Answer

HTLV-1

Question 9

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 10

Which mode of transmission is NOT considered parenteral for hepatitis?

Accepted Answer

Hepatitis A

Answer

Hepatitis B

Answer

Hepatitis C

Answer

Hepatitis D

Virology — MCQs

Virology — MCQs

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