Virology — MCQs
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Which of the following statements about Lambda phage is true:
The only serological marker present during window period in hepatitis B infection is?
Dangerous type of Herpes virus -
Antigenic shift and drift occur in
All are transmitted by blood except -
Which is the most common etiologic agent of acute infantile gastroenteritis?
Which of the following is associated with nasopharyngeal cancer?
The most predominant type of polio virus during epidemics is
Group of viruses that inhabit the alimentary tract of children below 2 years age:
Japanese encephalitis is caused by -
Virology Indian Medical PG Practice Questions and MCQs
Question 1261: Which of the following statements about Lambda phage is true:
- A. Lysogenic form incorporates with host DNA and remains dormant (Correct Answer)
- B. Causes mad cow disease
- C. Lytic and lysogenic interconversion cannot occur
- D. Lytic form incorporates within host DNA and multiplies causing rupture of cell membrane
Explanation: ***Lysogenic form incorporates with host DNA and remains dormant*** - In the **lysogenic cycle**, the **Lambda phage DNA** integrates into the host bacterial chromosome, becoming a **prophage**. - The prophage replicates along with the host DNA but does not immediately produce new phage particles, effectively remaining **dormant**. *Causes mad cow disease* - **Mad cow disease (Bovine Spongiform Encephalopathy)** is caused by **prions**, which are misfolded proteins, not by the Lambda phage. - Lambda phage is a **bacteriophage** that infects bacteria. *Lytic and lysogenic interconversion cannot occur* - **Lambda phage** is a classic example of a **temperate phage**, meaning it can switch between the **lytic** and **lysogenic cycles**. - Environmental cues or stress can induce a prophage to excise from the host DNA and enter the lytic cycle. *Lytic form incorporates within host DNA and multiplies causing rupture of cell membrane* - In the **lytic cycle**, the phage does not incorporate its DNA into the host chromosome; instead, it rapidly **replicates** within the host cell. - This leads to the production of many new phage particles, eventually causing the **lysis** (rupture) of the host cell membrane and release of progeny phages.
Question 1262: The only serological marker present during window period in hepatitis B infection is?
- A. HBeAg
- B. Anti HBc (Correct Answer)
- C. Anti HBsAg
- D. HBsAg
Explanation: ***Anti HBc*** - During the **window period**, neither **HBsAg** (due to immune clearance) nor **anti-HBs** (not yet detectable) are present. - **Anti-HBc IgM** is the first antibody to appear and remains detectable, making it the sole serological marker of acute infection during this phase. *HBeAg* - **HBeAg** indicates active viral replication and high infectivity, but it typically disappears before the window period as the immune system starts to control the infection. - Its presence is associated with viremia, which can fall below detectable levels during the window phase. *Anti HBsAg* - **Anti-HBs** signifies immunity (either from vaccination or resolved infection) but is not yet present during the window period. - During the window, the immune system is actively clearing HBsAg, but the anti-HBs antibodies have not reached detectable levels. *HBsAg* - **HBsAg** is the primary marker of active hepatitis B infection, but it disappears from the blood during the window period as antibodies begin to clear it. - The "window period" is specifically defined by the absence of detectable HBsAg and anti-HBs.
Question 1263: Dangerous type of Herpes virus -
- A. Cytomegalovirus
- B. Epstein Barr virus
- C. Herpes simplex-2
- D. Herpes virus simiae (Correct Answer)
Explanation: ***Herpes virus simiae*** - **Herpes virus simiae**, also known as **B virus**, is extremely dangerous to humans, often leading to severe neurological disease or death if an infection occurs. - It is naturally found in **macaques** and can be transmitted to humans through bites, scratches, or exposure to infected tissues or fluids. *Cytomegalovirus* - **Cytomegalovirus (CMV)** is generally benign in healthy individuals, causing mild or asymptomatic infections. - While CMV can be severe in immunocompromised patients or neonates (leading to **congenital CMV**), it is not inherently as dangerous as Herpes virus simiae in healthy individuals. *Epstein Barr virus* - **Epstein-Barr virus (EBV)** is famous for causing **infectious mononucleosis** in humans. - Although it can be associated with certain cancers like **Burkitt lymphoma** and **nasopharyngeal carcinoma**, it is not acutely "dangerous" in the same immediate, life-threatening way as Herpes virus simiae upon initial infection in healthy hosts. *Herpes simplex-2* - **Herpes simplex virus type 2 (HSV-2)** is the primary cause of genital herpes. - While it causes recurrent, painful lesions and can lead to **neonatal herpes** (which is serious), it does not typically cause the rapid, fatal neurological disease seen with Herpes virus simiae in humans.
Question 1264: Antigenic shift and drift occur in
- A. Rubella
- B. Influenza (Correct Answer)
- C. Measles
- D. Mumps
Explanation: ***Influenza*** - Influenza viruses undergo both **antigenic drift** (minor mutations in surface antigens, leading to new seasonal strains) and **antigenic shift** (major genetic reassortment, leading to novel strains like pandemic flu). - These mechanisms allow the virus to **evade host immunity**, necessitating frequent vaccine updates. *Rubella* - The rubella virus (German measles) is a **Togavirus** that is generally genetically stable. - It does not exhibit significant antigenic drift or shift, which is why a single **MMR vaccine** provides long-lasting immunity. *Measles* - The measles virus (Rubeola) is a **Paramyxovirus** and is known for its genetic stability. - Due to its lack of significant antigenic variation, vaccination provides **lifelong immunity**, and herd immunity can be achieved. *Mumps* - The mumps virus, also a **Paramyxovirus**, is relatively genetically stable. - It does not undergo antigenic drift or shift to the extent seen in influenza, making the **MMR vaccine** effective for long-term protection.
Question 1265: All are transmitted by blood except -
- A. Parvovirus B-19
- B. Cytomegalovirus
- C. Hepatitis G
- D. Epstein-Barr virus (Correct Answer)
Explanation: **Epstein-Barr virus** - While Epstein-Barr virus can be detected in blood, its primary mode of transmission is through **saliva** (e.g., kissing, sharing utensils), leading to infectious mononucleosis. - **Blood transfusion transmission** of EBV is rare and not considered a major route of spread in otherwise healthy individuals. *Parvovirus B-19* - **Parvovirus B-19** is well-known to be transmitted via **blood products** and can cause transient aplastic crisis, especially in patients with chronic hemolytic anemias. - It can also be transmitted via **respiratory droplets** and vertically from mother to fetus. *Cytomegalovirus* - **Cytomegalovirus (CMV)** is frequently transmitted through **blood transfusions**, especially to immunocompromised patients. - It can also be transmitted through other bodily fluids, organ transplantation, and congenitally. *Hepatitis G* - **Hepatitis G virus (HGV)**, now renamed **GB virus C (GBV-C)**, is primarily transmitted through **blood** and blood products. - It is often found as a co-infection with hepatitis C virus but its pathogenicity remains controversial.
Question 1266: Which is the most common etiologic agent of acute infantile gastroenteritis?
- A. Adenovirus
- B. Norwalk virus
- C. Rotavirus (Correct Answer)
- D. E. coli
Explanation: ***Rotavirus*** - **Rotavirus** is the leading cause of **severe, dehydrating gastroenteritis** in infants and young children worldwide. - It is highly contagious and spreads via the **fecal-oral route**, causing symptoms like **vomiting, watery diarrhea**, and fever. *Adenovirus* - While adenoviruses can cause gastroenteritis, they are responsible for a **smaller percentage** of cases compared to rotavirus. - Adenovirus infections tend to cause **milder symptoms** and less severe dehydration. *Norwalk virus* - **Norwalk virus**, now classified as **Norovirus**, is a common cause of **gastroenteritis in all age groups**, including children. - However, it is more often associated with **outbreaks in older children and adults**, and rotavirus remains the primary cause in infants. *E. coli* - **Escherichia coli (E. coli)** can cause various forms of gastroenteritis, particularly **enterotoxigenic E. coli (ETEC)** and **enterohemorrhagic E. coli (EHEC)**. - While significant, E. coli is not the **most common overall etiologic agent** for acute infantile gastroenteritis compared to rotavirus.
Question 1267: Which of the following is associated with nasopharyngeal cancer?
- A. Herpes Simplex Virus 1 (HSV-1)
- B. Epstein-Barr Virus (EBV) (Correct Answer)
- C. Herpes Simplex Virus 2 (HSV-2)
- D. Varicella-Zoster Virus (VZV)
Explanation: ***Epstein-Barr Virus (EBV)*** - **Epstein-Barr Virus** is strongly and consistently associated with the development of **nasopharyngeal carcinoma (NPC)**, particularly the undifferentiated type. - EBV DNA is often detected in NPC tumor cells, and the virus plays a significant role in **tumorigenesis**. *Herpes Simplex Virus 1 (HSV-1)* - **HSV-1** is primarily associated with **oral herpes** (cold sores) and occasionally **genital herpes**, but not nasopharyngeal cancer. - While it establishes latency in neurons, there is no direct causal link between HSV-1 infection and NPC. *Herpes Simplex Virus 2 (HSV-2)* - **HSV-2** is the main cause of **genital herpes** and is transmitted sexually, but it is not associated with nasopharyngeal cancer. - It establishes latency in sacral ganglia, and its oncogenic potential is primarily linked to cervical cancer in conjunction with HPV, not NPC. *Varicella-Zoster Virus (VZV)* - **VZV** causes **chickenpox** (varicella) in children and **shingles** (herpes zoster) in adults, but it is not linked to nasopharyngeal cancer. - VZV establishes latency in sensory ganglia and reactivates to cause neurological and dermatological symptoms.
Question 1268: The most predominant type of polio virus during epidemics is
- A. Type III
- B. Type II
- C. Type I (Correct Answer)
- D. Combined infection of II & III
Explanation: ***Type I*** - **Type 1 poliovirus** is historically the most common cause of **paralytic polio** and is responsible for the majority of outbreaks and epidemics globally. - Its high **neurovirulence** and efficient transmission contribute to its predominance in epidemic settings. - **Type 1** accounts for approximately **80-85%** of paralytic polio cases historically. *Type III* - While **Type 3 poliovirus** can cause paralytic polio, it is less frequently isolated during epidemics compared to Type 1. - The last reported case of **wild Type 3 poliovirus** was in November 2012, and it was officially declared eradicated by WHO in October 2019. *Type II* - **Type 2 poliovirus** is associated with a lower incidence of **paralytic disease** and was declared eradicated in September 2015. - It is no longer found in **wild circulation** and is not the predominant type in current epidemics. *Combined infection of II & III* - While co-infections with different poliovirus types were possible historically, **Type 1** remains the single most common and predominant type during epidemics, driving the majority of cases. - **Type 2** and **Type 3** wild polioviruses have been eradicated, making combined wild-type infections impossible in current global epidemiology.
Question 1269: Group of viruses that inhabit the alimentary tract of children below 2 years age:
- A. Varicella zoster virus
- B. Coxsackie virus (Correct Answer)
- C. Herpes simplex virus
- D. Paramyxovirus
Explanation: ***Coxsackie virus*** - **Coxsackieviruses** are a common cause of infections in young children, often leading to conditions like **hand-foot-and-mouth disease** or herpangina, which involve the alimentary tract. - These viruses replicate in the **gastrointestinal tract** and are a frequent cause of viral infections in children under two years of age. *Varicella zoster virus* - This virus is responsible for **chickenpox** and **shingles**, primarily affecting the skin and nervous system, not typically inhabiting the alimentary tract as its primary site of replication or causing symptoms in the gut. - While it can be found in the body, it is not a virus group commonly associated with routine alimentary tract habitation in young children in the way enteroviruses are. *Herpes simplex virus* - **HSV-1** and **HSV-2** primarily cause mucocutaneous lesions (e.g., cold sores, genital herpes) and can cause encephalitis, but they do not typically colonize or primarily inhabit the alimentary tract of children. - While oral HSV-1 infections are common in children, the virus's primary tropism is for **neural tissue** and epithelial cells, not a general alimentary tract dwelling. *Paramyxovirus* - This family includes viruses like **measles, mumps, and respiratory syncytial virus (RSV)**, which primarily cause respiratory infections and systemic diseases. - They are not known for inhabiting the alimentary tract of children as their main site of infection or replication in the same manner as enteroviruses.
Question 1270: Japanese encephalitis is caused by -
- A. Culex
- B. Flavivirus (Correct Answer)
- C. Pigs
- D. None of the options
Explanation: ***Flavivirus*** - **Japanese encephalitis** is an **arboviral disease** caused by the **Japanese encephalitis virus (JEV)**, which belongs to the genus *Flavivirus* within the family *Flaviviridae*. - This **RNA virus** is primarily transmitted to humans through the bite of infected mosquitoes. *Culex* - While mosquitoes of the genus *Culex* (especially *Culex tritaeniorhynchus*) are the **primary vectors** that transmit the Japanese encephalitis virus, they are not the causative agent themselves. - *Culex* mosquitoes acquire the virus from infected animals and then transmit it to humans. *Pigs* - **Pigs** are considered **amplifying hosts** for the Japanese encephalitis virus, meaning the virus replicates to high levels in them and can then infect mosquitoes. - However, pigs do not directly cause the disease in humans; they act as a reservoir in the transmission cycle. *None of the options* - This option is incorrect as **Flavivirus** is indeed the causative agent of Japanese encephalitis.
Practice by Chapter
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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Enteroviruses and Rhinoviruses
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Arboviruses
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HIV and Retroviruses
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Oncogenic Viruses
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