RNA Viruses: Orthomyxoviruses — MCQs
Which receptors do avian influenza HA viruses primarily bind to?
True about influenza -
A man with chills, fever, and headache is thought to have "atypical" pneumonia. History reveals that he raises chickens, and that approximately 2 weeks ago he lost a large number of them to an undiagnosed disease. Which of the following is the most likely diagnosis of this man's condition?
Which of the following medications is not indicated for the treatment or prophylaxis of seasonal influenza?
During the discharge of a COVID patient treated with steroids and remdesivir, which of the following will you inform him about? 1. Repeat RT-PCR after 7 days of discharge 2. Watch for the persistence of Anosmia 3. Watch for headache and nasal discharge 4. Monitor glucose levels 5. Watch for Sinusitis symptoms
Which of the following does not have a viral etiology?
In lymphoid tissue biopsy from a patient with suspected measles, multinucleated giant cells with 'clockwise' nuclear arrangement are observed. What are these cells called?
A 20-year-old woman presents with headache, fever, and neck stiffness. On examination, her blood pressure is 100/70 mm Hg, pulse 100/min, temperature 38.6, and the neck is stiff and painful to flex and extend. The ears, throat, and sinuses are normal, there are no focal neurologic signs, and the remaining examination is normal. There are no reported similar cases in the community. Which of the following is the most likely source of her infection?
Which of the following statements about Norwalk virus is false?
How many segments of RNA does the Influenza virus have?
RNA Viruses: Orthomyxoviruses Indian Medical PG Practice Questions and MCQs
Question 1: Which receptors do avian influenza HA viruses primarily bind to?
- A. Alpha 2-9 sialic acid receptors
- B. Alpha 2-6 sialic acid receptors
- C. Alpha 2-8 sialic acid receptors
- D. Alpha 2-3 sialic acid receptors (Correct Answer)
Explanation: ***Alpha 2-3 sialic acid receptors*** - Avian influenza viruses preferentially bind to **alpha 2-3 sialic acid receptors**, which are abundant in the **gastrointestinal tract of birds**. - This specificity explains why these viruses primarily infect birds and generally require adaptation to infect humans efficiently. - The α2-3 linkage configuration allows optimal binding of avian HA proteins. *Alpha 2-6 sialic acid receptors* - These receptors are the **primary binding targets for human-adapted influenza A viruses**, found abundantly in the **human upper respiratory tract**. - Avian influenza viruses typically bind less efficiently to α2-6 receptors unless specific mutations occur in the HA protein. - The shift from α2-3 to α2-6 binding preference is a key adaptation for human transmission. *Alpha 2-8 sialic acid receptors* - Alpha 2-8 linkages exist in **polysialic acid chains** and certain gangliosides but are **not recognized binding targets for influenza HA proteins**. - Influenza viruses specifically recognize α2-3 or α2-6 linkages, not α2-8. *Alpha 2-9 sialic acid receptors* - Alpha 2-9 linkages are **not biologically relevant receptors for influenza viruses**. - The key receptor specificity determinant for influenza is the distinction between α2-3 (avian) and α2-6 (human) linkages.
Question 2: True about influenza -
- A. Incubation period 2-3 weeks
- B. Pandemic is caused by Type-B virus
- C. Most infections are subclinical (Correct Answer)
- D. Type-A virus causes Reye's syndrome
Explanation: **Most infections are subclinical** - Many individuals infected with influenza virus experience **mild symptoms** or no symptoms at all, making the infection subclinical. - This characteristic contributes significantly to the **spread of the virus**, as asymptomatic carriers can unknowingly transmit it. *Incubation period 2-3 weeks* - The typical incubation period for influenza is much shorter, usually **1 to 4 days**, with an average of 2 days [1]. - An incubation period of 2-3 weeks would be more characteristic of other viral infections, such as **chickenpox** or **measles**. *Pandemic is caused by Type-B virus* - **Influenza A virus** is primarily responsible for pandemics due to its ability to undergo both **antigenic drift** and **antigenic shift**, leading to novel viral strains that can spread globally [1]. - Influenza B viruses primarily cause **seasonal epidemics**, often affecting children more severely, and do not typically cause pandemics. *Type-A virus causes Reye's syndrome* - Reye's syndrome is a rare but severe condition associated with the use of **aspirin** (salicylates) in children recovering from certain viral infections, including **influenza A or B** and **chickenpox**. - It is not directly caused by the influenza virus itself but is a medication-related complication in the context of a viral infection, making aspirin use a contraindication in pediatric viral illnesses.
Question 3: A man with chills, fever, and headache is thought to have "atypical" pneumonia. History reveals that he raises chickens, and that approximately 2 weeks ago he lost a large number of them to an undiagnosed disease. Which of the following is the most likely diagnosis of this man's condition?
- A. Leptospirosis
- B. Relapsing fever
- C. Anthrax
- D. Ornithosis (Correct Answer)
Explanation: ***Ornithosis*** - The patient's symptoms of **chills, fever, headache, and atypical pneumonia**, combined with a history of **raising chickens** that recently died from an undiagnosed disease, are highly suggestive of ornithosis (also known as **psittacosis** or **parrot fever**). [2], [3] - This zoonotic infection is caused by **Chlamydophila psittaci** and is transmitted to humans through inhalation of contaminated aerosols from infected birds (poultry, parrots, pigeons). [2] *Leptospirosis* - **Leptospirosis** is typically associated with exposure to **contaminated water or soil** with animal urine, not direct contact with sick poultry. - While it can cause fever and headache, it often presents with **jaundice, renal failure, and hemorrhagic manifestations**, which are not mentioned here. *Relapsing fever* - **Relapsing fever** is characterized by **recurrent episodes of fever** separated by afebrile periods, caused by **Borrelia** species transmitted by lice or ticks. - The clinical presentation does not align with the typical course or epidemiological link to sick chickens. *Anthrax* - **Inhalational anthrax** can cause severe respiratory symptoms and fever but is primarily associated with exposure to **Bacillus anthracis spores**, often from infected livestock (cattle, sheep) or bioweapon exposure. [1] - The rapid death of a large number of chickens and the patient's "atypical pneumonia" do not fit the typical presentation or common transmission routes of anthrax. [1]
Question 4: Which of the following medications is not indicated for the treatment or prophylaxis of seasonal influenza?
- A. Amantadine
- B. Rimantadine
- C. Oseltamivir
- D. Acyclovir (Correct Answer)
Explanation: ***Acyclovir*** - **Acyclovir** is an antiviral medication specifically used to treat infections caused by **herpes viruses** (e.g., HSV, VZV), not influenza viruses. - It works by inhibiting **viral DNA polymerase**, a mechanism distinct from how anti-influenza drugs act. - **This drug has never been indicated for influenza** - it is the correct answer to this "not indicated" question. *Amantadine* - **Amantadine** is an M2 ion channel inhibitor that **was indicated** for influenza A treatment and prophylaxis. - Although no longer recommended due to widespread **resistance** among circulating influenza strains, it remains a drug that was formally indicated for seasonal influenza. *Rimantadine* - **Rimantadine** is also an M2 ion channel inhibitor, structurally related to amantadine, with a similar mechanism of action. - Like amantadine, it **was indicated** for influenza treatment or prophylaxis but is no longer recommended due to high rates of **resistance** in circulating influenza A viruses. *Oseltamivir* - **Oseltamivir** is a **neuraminidase inhibitor** currently approved and recommended for the treatment and prophylaxis of both influenza A and B. - It reduces viral spread by preventing the release of new virions from infected cells and remains a first-line agent for seasonal influenza.
Question 5: During the discharge of a COVID patient treated with steroids and remdesivir, which of the following will you inform him about? 1. Repeat RT-PCR after 7 days of discharge 2. Watch for the persistence of Anosmia 3. Watch for headache and nasal discharge 4. Monitor glucose levels 5. Watch for Sinusitis symptoms
- A. 1,3 and 4
- B. 3,4 and 5 (Correct Answer)
- C. 2,3 and 4
- D. 1,2,3,4 and 5
Explanation: **3, 4, and 5** - For patients treated with **steroids**, it is crucial to monitor **glucose levels** due to the potential for steroid-induced hyperglycemia [1]. - Symptoms like **headache** and **nasal discharge** (and by extension **sinusitis symptoms**) could indicate conditions like **mucormycosis**, a serious fungal infection seen in immunocompromised COVID-19 patients, especially those having received steroids. *1, 3, and 4* - A **repeat RT-PCR after 7 days** of discharge is generally not recommended as per current guidelines, as viral shedding can persist without infectivity. - While monitoring for headache, nasal discharge, and glucose levels is appropriate, omitting the direct vigilance for **sinusitis symptoms** is less comprehensive. *2, 3, and 4* - While **anosmia** (loss of smell) can persist post-COVID, it is primarily a lingering symptom of the infection itself and typically resolves spontaneously, not usually requiring specific discharge instructions for monitoring its persistence to prevent complications. - The focus should be on new or worsening symptoms that might indicate post-COVID complications or secondary infections. *1, 2, 3, 4, and 5* - Including **repeat RT-PCR** and solely "watch for the persistence of Anosmia" without emphasizing resolution or specific actions makes this option less pertinent for discharge advice. - The priority for discharge instructions should be preventable complications and warning signs of serious conditions.
Question 6: Which of the following does not have a viral etiology?
- A. Hepatocellular carcinoma
- B. Nasopharyngeal carcinoma
- C. Colorectal adenocarcinoma
- D. Breast ductal carcinoma (Correct Answer)
Explanation: ***Hodgkin's lymphoma*** - Hodgkin's lymphoma is primarily associated with **genetic factors** and environmental triggers instead of a viral cause [1][2]. - It can arise from **Reed-Sternberg cells**, which are not related to viral infections [1][2]. - EBV is not associated with certain subtypes of Hodgkin lymphoma [3]. *Nasopharyngeal carcinoma* - Strongly linked to **Epstein-Barr virus (EBV)**, which plays a significant role in its pathogenesis. - It is characterized by **nasal obstruction** and symptoms related to tumor invasion, with a clear viral etiology. *Hepatocellular carcinoma* - Often associated with **hepatitis B and C viruses**, which are well-known risk factors for liver cancer. - Chronic infection leads to **cirrhosis**, predisposing individuals to carcinoma development. *Burkitt's lymphoma* - Associated with **EBV**, particularly in endemic forms in Africa, affecting the jaw or abdomen [4]. - It involves **aggressive B-cell proliferation**, strongly linked to viral infection [4]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 556-557. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 614-616. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 618. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 335-336.
Question 7: In lymphoid tissue biopsy from a patient with suspected measles, multinucleated giant cells with 'clockwise' nuclear arrangement are observed. What are these cells called?
- A. Cowdry type A
- B. Warthin-Finkeldey cells (Correct Answer)
- C. Negri bodies
- D. Henderson-Paterson bodies
Explanation: ***Warthin-Finkeldey cells*** - These are **multinucleated giant cells** with many nuclei arranged in a **\"clockwise\" or syncytial pattern**, a characteristic histopathological finding in **lymphoid tissues (lymph nodes, tonsils, spleen) during prodromal measles**. - They represent a key diagnostic marker for measles infection, formed by the fusion of infected lymphoid cells. - They are typically found **before the appearance of the measles rash**. *Cowdry type A* - **Cowdry type A inclusion bodies** are intranuclear inclusions characteristic of **herpes simplex virus** and **varicella-zoster virus** infections. - They are eosinophilic inclusions surrounded by a clear halo, seen in herpesvirus-infected cells, not measles. *Negri bodies* - **Negri bodies** are eosinophilic, cytoplasmic inclusion bodies found in neurons (especially hippocampal pyramidal cells), characteristic of **rabies infection**. - They are pathognomonic for rabies virus and are not observed in measles. *Henderson-Paterson bodies* - **Henderson-Paterson bodies** are large, eosinophilic intracytoplasmic inclusions (molluscum bodies) found in epidermal cells infected with **molluscum contagiosum virus**. - They are pathognomonic for molluscum contagiosum and have no association with measles.
Question 8: A 20-year-old woman presents with headache, fever, and neck stiffness. On examination, her blood pressure is 100/70 mm Hg, pulse 100/min, temperature 38.6, and the neck is stiff and painful to flex and extend. The ears, throat, and sinuses are normal, there are no focal neurologic signs, and the remaining examination is normal. There are no reported similar cases in the community. Which of the following is the most likely source of her infection?
- A. skin
- B. oral ingestion
- C. an infected heart valve
- D. nasopharynx (Correct Answer)
Explanation: ***Nasopharynx*** - The nasopharynx is a common reservoir for **meningitis-causing bacteria** such as *Neisseria meningitidis* and *Streptococcus pneumoniae*. - These bacteria can colonize the nasopharynx without causing local illness and then cross the mucosal barrier to enter the bloodstream, eventually reaching the **meninges**. *Skin* - Skin infections typically cause **localized symptoms** such as redness, swelling, and pain, possibly with pus formation. - While skin infections can lead to bacteremia and distant infections, there are no skin lesions or signs of infection mentioned in this case. *Oral ingestion* - Oral ingestion typically leads to **gastrointestinal symptoms** such as nausea, vomiting, or diarrhea. - While some pathogens ingested orally can spread systemically, it is not the most direct or common route for the symptoms described. *An infected heart valve* - An infected heart valve (endocarditis) would commonly present with **new heart murmurs**, **constitutional symptoms** (fever, fatigue), and signs of **embolism**, which are not mentioned here [1]. - While endocarditis can cause bacteremia and systemic spread, it would typically have more distinct cardiac findings. *General Clinical Presentation* - Headache, fever, and neck stiffness (meningism) are the classic presenting features of bacterial meningitis [1].
Question 9: Which of the following statements about Norwalk virus is false?
- A. Is a RNA virus
- B. Causes gastroenteritis
- C. Cultivated in cell culture (Correct Answer)
- D. Belongs to Caliciviridae
Explanation: ***Cultivated in cell culture*** - **Norwalk virus** (now known as **norovirus**) is notoriously difficult to cultivate in standard laboratory cell cultures, making research and vaccine development challenging. - Its inability to grow in vitro is a defining characteristic, differentiating it from many other common viruses. *Belongs to calciviridae* - This statement is **true**; Norwalk virus is the prototype and best-known member of the genus *Norovirus* within the family **Caliciviridae**. - **Caliciviridae** are a family of non-enveloped, positive-sense, single-stranded RNA viruses. *Causes gastroenteritis* - This statement is **true**; Norovirus is the leading cause of **acute gastroenteritis** worldwide, particularly in outbreaks in crowded settings such as cruise ships, hospitals, and schools. - It causes symptoms like **nausea, vomiting, diarrhea**, and abdominal cramps. *Is a RNA virus* - This statement is **true**; Norovirus has a **single-stranded, positive-sense RNA genome**. - Its RNA genome is essential for its replication cycle as it can directly serve as mRNA.
Question 10: How many segments of RNA does the Influenza virus have?
- A. 5 segments of single-stranded RNA
- B. 8 segments of double-stranded DNA
- C. 8 segments of single-stranded DNA
- D. 8 segments of single-stranded RNA (Correct Answer)
Explanation: ***8 segments of single-stranded RNA*** - The **Influenza virus** is characterized by its segmented genome, which consists of **eight distinct negative-sense single-stranded RNA (ssRNA)** molecules. - This segmentation is crucial for its high mutation rate and ability to undergo **antigenic shift** and **antigenic drift**, leading to new strains. *5 segments of single-stranded RNA* - This option is incorrect because the Influenza virus specifically has **eight segments**, not five. - While it is a single-stranded RNA virus, the number of segments is a key characteristic. *8 segments of double-stranded DNA* - This option is incorrect as Influenza is an **RNA virus**, not a DNA virus, and its genetic material is single-stranded, not double-stranded. - No known influenza viruses have a **double-stranded DNA genome**. *8 segments of single-stranded DNA* - This option is incorrect because Influenza is an **RNA virus**, not a DNA virus. - Its genetic material is composed of **RNA**, specifically negative-sense single-stranded RNA.
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