Question 1

Picornaviridae taxonomy refresher: Which genera are included within the family Picornaviridae for human medicine and classic teaching?

Accepted Answer

Introduction: Picornaviridae are small, non-enveloped, positive-sense RNA viruses of major clinical importance. A common exam task is to recognize which familiar genera belong to this family. Given Data / Assumptions: Genera listed: Enterovirus (polio, coxsackie, echo), Rhinovirus (common cold), Hepatovirus (hepatitis A virus). Family features: icosahedral capsid, positive-sense RNA, cytoplasmic replication. We select inclusion within Picornaviridae. Concept / Approach: Enterovirus, Rhinovirus, and Hepatovirus are canonical picornavirus genera in medical microbiology texts. They differ in acid stability and tissue tropism, but share genome organization and replication strategy typical of picornaviruses. Step-by-Step Solution: List the classic human-related picornavirus genera. Confirm each listed genus is recognized as part of Picornaviridae. Choose the aggregate answer that includes all three. Select “All of these.” Verification / Alternative check: Standard family trees place poliovirus (Enterovirus), rhinoviruses, and HAV (Hepatovirus) squarely under Picornaviridae, despite ecological differences. Why Other Options Are Wrong: Any single genus choice is incomplete; “None” contradicts well-established taxonomy. Common Pitfalls: Assuming rhinoviruses are excluded because they are acid-labile; acid lability does not change family placement. Final Answer: All of these.

Question 2

Aseptic meningitis – causative picornaviruses: Which listed viruses are well-known causes of aseptic (viral) meningitis outbreaks in humans?

Accepted Answer

Introduction: Aseptic meningitis most often has viral etiologies. Among enteroviruses (a subset of Picornaviridae), several groups classically cause community outbreaks, particularly in summer and early fall. Recognizing these causative agents is key in clinical microbiology and epidemiology. Given Data / Assumptions: Candidate groups include polioviruses, coxsackieviruses, and echoviruses. We focus on historic and textbook associations. We select the most inclusive correct option. Concept / Approach: Multiple enteroviruses can cause aseptic meningitis. Coxsackie A/B and echoviruses are frequent culprits; poliovirus can also cause aseptic meningitis (separate from paralytic disease) as part of its spectrum. Therefore, all three categories belong on the list of recognized causes. Step-by-Step Solution: Identify which virus groups are enteroviruses. Recall their clinical syndromes including meningitis. Select the aggregate option encompassing all three. Choose “All of these.” Verification / Alternative check: Public health bulletins and textbooks consistently report seasonal aseptic meningitis due to coxsackie and echo viruses; poliovirus can present with febrile illness and meningitis without paralysis. Why Other Options Are Wrong: Single selections are incomplete; “None” is contradicted by abundant epidemiology. Common Pitfalls: Assuming poliovirus only causes paralysis; many infections are subclinical or present as aseptic meningitis without paralysis. Final Answer: All of these.

Question 3

Poxviridae in human disease: Which listed poxvirus genera include species that cause disease in humans?

Accepted Answer

Introduction: Poxviruses are large, enveloped DNA viruses with complex symmetry. Several genera contain pathogens relevant to human health. Recognizing which genera matter clinically helps guide differential diagnosis of vesiculopustular eruptions and nodular lesions. Given Data / Assumptions: Orthopoxvirus includes variola (smallpox), vaccinia, monkeypox. Parapoxvirus includes orf virus (zoonosis from sheep/goats). Molluscipoxvirus includes molluscum contagiosum virus. Concept / Approach: All three listed genera contain human pathogens—some historically devastating (variola), some re-emerging (monkeypox), and some producing benign but contagious lesions (molluscum). Thus, the comprehensive correct selection is “All of these.” Step-by-Step Solution: Match each genus to a human disease. Orthopox → smallpox/monkeypox; Parapox → orf; Molluscipox → molluscum contagiosum. Confirm multiple genera are involved. Select “All of these.” Verification / Alternative check: Clinical dermatology references list characteristic lesion morphologies for each genus and document human cases globally. Why Other Options Are Wrong: Any single genus is incomplete; “None” is contradicted by well-known human infections. Common Pitfalls: Assuming parapox viruses are purely veterinary; orf is a classical occupational zoonosis in humans. Final Answer: All of these.

Question 4

Transmission routes – Molluscum contagiosum: How is molluscum contagiosum virus commonly transmitted in the community and in adults?

Accepted Answer

Introduction: Molluscum contagiosum virus (a poxvirus) produces umbilicated papules on skin. Understanding transmission helps with counseling, prevention, and infection control in schools, sports, and sexual health clinics. Given Data / Assumptions: Viral lesions contain infectious material. Fomites and skin-to-skin exposure facilitate spread. In adults, genital lesions are often sexually transmitted. Concept / Approach: The chief route is direct contact with lesions or contaminated objects (e.g., towels, razors, wrestling mats). In sexually active adults, sexual contact is an important mode. Therefore, the best answer that captures both community and sexual contexts is “Both (a) and (b).” Step-by-Step Solution: Identify contact as the main mechanism of spread. Recognize a special case: sexual transmission among adults. Choose the option that includes both routes. Select “Both (a) and (b).” Verification / Alternative check: Dermatology guidelines emphasize contact precautions and patient education about avoiding shaving lesion areas and sharing personal items; sexual health resources note transmission via intimate skin contact. Why Other Options Are Wrong: Direct only – incomplete; omits sexual transmission. Sexual only – incomplete; children commonly acquire via nonsexual contact. None/Airborne – airborne spread is not the principal mode. Common Pitfalls: Assuming a respiratory route similar to varicella; molluscum is primarily a contact-spread dermatosis. Final Answer: Both (a) and (b).

Question 5

Acid stability among picornaviruses: Which listed viruses are acid-labile (readily inactivated by gastric acid) and therefore typically confined to the upper respiratory tract rather than the gut?

Accepted Answer

Introduction: A classic distinguishing feature among picornaviruses is their response to acidic pH. Acid stability correlates with transmission route and tissue tropism. This item tests whether you can identify the acid-labile outlier responsible for common colds. Given Data / Assumptions: Enteroviruses (polio, coxsackie, echo) typically survive gastric acidity. Rhinoviruses are associated with the upper respiratory tract. We choose the virus group inactivated by stomach acid. Concept / Approach: Rhinoviruses are acid-labile and grow best at cooler temperatures of the nasal mucosa, favoring transmission by respiratory secretions and fomites. In contrast, enteroviruses are acid-stable, enabling fecal–oral spread and intestinal replication. Step-by-Step Solution: Partition picornaviruses into respiratory (rhinoviruses) and enteric (enteroviruses). Recall the acid sensitivity profile. Select the acid-labile group: rhinoviruses. Exclude enteroviruses that tolerate gastric pH. Verification / Alternative check: Laboratory conditions for rhinovirus culture use near-neutral pH and lower temperatures; enteroviruses survive simulated gastric fluid, matching their epidemiology. Why Other Options Are Wrong: Echoviruses, Polioviruses, Coxsackieviruses – all are enteroviruses and are characteristically acid-stable. None – incorrect because rhinoviruses are the well-known acid-labile group. Common Pitfalls: Confusing “labile” with “stable”; remember “rhino” for nose/respiratory and acid-labile. Final Answer: Rhinoviruses.

Question 6

Poxvirus morphology: What is the symmetry of the nucleocapsid of poxviruses as described in classic virology texts and electron microscopy?

Accepted Answer

Introduction: Most viruses are categorized by helical or icosahedral symmetry. Poxviruses are an exception and are frequently tested for their unusual architecture. Recognizing this exception prevents classification errors. Given Data / Assumptions: Poxviruses are large, brick-shaped, enveloped DNA viruses. They replicate in the cytoplasm despite being DNA viruses. The question asks for nucleocapsid symmetry. Concept / Approach: Electron microscopy shows that poxviruses have a complex symmetry—neither purely helical nor icosahedral. Their core, lateral bodies, and envelope form a distinctive structure not classifiable by the two standard categories, hence the term “complex.” Step-by-Step Solution: Recall typical viral symmetries: helical and icosahedral. Identify poxviruses as the classic exception with complex architecture. Select “Complex.” Exclude the standard geometries. Verification / Alternative check: Atlases of electron micrographs depict the brick-like virion with dumbbell-shaped core and lateral bodies, validating the complex classification. Why Other Options Are Wrong: Icosahedral/Helical – do not describe poxvirus structure. All/None – “All” is incorrect because only “Complex” applies; “None” ignores the accepted terminology. Common Pitfalls: Assuming all DNA viruses have icosahedral capsids; poxviruses are a major exception. Final Answer: Complex.

Question 7

Herpangina etiology: Within the coxsackievirus groups, which group is classically associated with herpangina (painful vesicles and ulcers on the soft palate/tonsillar pillars)?

Accepted Answer

Introduction: Herpangina is an enteroviral illness characterized by sudden fever, sore throat, and small vesicular lesions on the posterior oropharynx. Identifying the principal viral group helps with clinical recognition and counseling during seasonal outbreaks. Given Data / Assumptions: Coxsackieviruses are divided into group A and group B. Multiple clinical syndromes are associated with these groups. We select the group most strongly linked to herpangina. Concept / Approach: Coxsackie A viruses (several serotypes) are classically associated with herpangina and hand-foot-and-mouth disease. Group B more often causes pleurodynia, myocarditis, and pericarditis. Therefore, the correct selection for herpangina in exam settings is group A. Step-by-Step Solution: List major coxsackievirus clinical associations. Match herpangina to the group A cluster of diseases. Select “Group A.” Exclude group B and distractors. Verification / Alternative check: Outbreak summaries attribute herpangina primarily to group A serotypes (e.g., A1–A10, A12, A22, A24), aligning with classic teaching. Why Other Options Are Wrong: Group B – associated more with chest pain syndromes and cardiac involvement. Both/None – “both” overstates the association; “none” contradicts epidemiology. Echovirus group – echoviruses can cause pharyngitis or meningitis but herpangina is classically linked to coxsackie A. Common Pitfalls: Confusing hand-foot-and-mouth disease (often coxsackie A16 or enterovirus A71) with herpangina; they overlap but are distinct syndromes. Final Answer: Group A.

Question 8

Orthopoxvirus diseases: Which human and animal diseases are caused by members of the genus Orthopoxvirus (consider classic examples such as vaccinia, variola, and cowpox)?

Accepted Answer

Introduction: Orthopoxvirus is a genus within the Poxviridae family that includes medically important viruses historically and currently relevant to humans and animals. Understanding which specific diseases are caused by Orthopoxvirus members reinforces taxonomy, host range, and public health history. Given Data / Assumptions: The options list vaccinia, smallpox (variola), and cowpox as possible diseases. Orthopoxviruses are large, enveloped DNA viruses that replicate in the cytoplasm. The question seeks which diseases in the list are associated with Orthopoxvirus. Concept / Approach: Key Orthopoxvirus members include Variola virus (smallpox), Vaccinia virus (used in smallpox vaccine and recombinant vectors), Cowpox virus (zoonotic infections), and Monkeypox virus. These viruses share antigenic relatedness, which enabled cross-protection and eradication strategies for smallpox. If several listed diseases are known Orthopoxvirus infections, the inclusive answer is appropriate. Step-by-Step Solution: Identify variola as the agent of smallpox, a historic Orthopoxvirus. Recognize vaccinia as the vaccine strain, also an Orthopoxvirus. Recall cowpox as a zoonotic Orthopoxvirus that infected milkers historically. Since all three are Orthopoxvirus diseases, select the comprehensive option. Verification / Alternative check: Standard virology texts place Variola, Vaccinia, and Cowpox viruses within Orthopoxvirus. Antigenic overlap among Orthopoxviruses is the foundation of cross-protection in vaccination history. Why Other Options Are Wrong: Vaccinia / Smallpox / Cowpox (alone): Each is correct but incomplete because multiple items are true simultaneously. None of these: Incorrect because all three listed diseases are caused by Orthopoxvirus members. Common Pitfalls: Assuming only variola is relevant; in fact, several Orthopoxvirus species cause human or veterinary disease. Another pitfall is confusing Orthopoxvirus with other pox genera such as Parapoxvirus. Final Answer: All of these are Orthopoxvirus diseases (vaccinia, smallpox, cowpox).

Question 9

Cell culture support for polioviruses: Which cell lines can support the growth of poliovirus in the laboratory?

Accepted Answer

Introduction: Poliovirus is a positive-sense RNA enterovirus historically propagated in tissue culture for research and vaccine production. Recognizing permissive cell lines is a classic laboratory virology competency. Given Data / Assumptions: Candidate cell lines include human amnion, monkey kidney, and HeLa. We assume standard lab conditions with appropriate media and temperature. Outcome of interest is ability to support poliovirus growth and cytopathic effect. Concept / Approach: Poliovirus has long been cultivated in primate-derived cell lines, notably monkey kidney cells, and also in continuous human cell lines such as HeLa. Human amnion cells can also support growth. If each listed line is permissive, the correct choice is the inclusive option. Step-by-Step Solution: Recall Salk and Sabin vaccine production history using primate kidney lines. Note the robust poliovirus replication and CPE documented in HeLa cells. Recognize human amnion cells as historically used for certain enteroviruses. Conclude all listed cell lines can support poliovirus growth. Verification / Alternative check: Classic virology lab manuals and historical vaccine literature document poliovirus propagation in these cells, confirming their permissiveness. Why Other Options Are Wrong: Any single line alone: Incomplete because more than one listed line is permissive. None of these: False because several listed lines are well established for poliovirus. Common Pitfalls: Equating historical primate kidney use with exclusivity; continuous human lines like HeLa are also suitable under appropriate conditions. Final Answer: All of these cell lines can support poliovirus growth.

Poxviridae and Picronaviridae Questions