22 Year 3: Medical Virology exam questions on Virology MCQs for medical students. Includes MCQs, answers, explanations and written questions. Sample: Which of t
This MCQ set contains 22 questions on Virology MCQs in the Year 3: Medical Virology unit. Each question includes the correct answer and a detailed explanation for active recall and exam preparation.
Correct answer: B – Most persons who are seropositive for HSV-2 but report no symptoms still shed virus from the genital area intermittently
Most HSV-2 seropositive individuals are asymptomatic but still shed virus intermittently from the genital mucosa — making them unknowing transmitters. This asymptomatic shedding is the primary driver of HSV-2 spread. HSV-2 is actually associated with increased HIV acquisition risk, making C false.
Correct answer: C – Lesions present, symptoms usually severe, HSV-1 and HSV-2 antibodies are not present
A true primary first episode HSV-2 infection means no prior HSV exposure of any type. Therefore both HSV-1 and HSV-2 antibodies are absent, and the clinical presentation is typically severe — extensive lesions, systemic symptoms (fever, malaise, lymphadenopathy), and prolonged viral shedding.
Correct answer: C – Retroviruses
Retroviruses (e.g., HIV) carry two identical copies of positive-sense single-stranded RNA and the enzyme reverse transcriptase, which converts viral RNA into DNA for integration into the host genome. This diploid RNA genome is unique to retroviruses among animal viruses.
Correct answer: E – Temperate phages
Temperate phages integrate their genome into the bacterial chromosome as a prophage, establishing a stable long-term lysogenic relationship with the host. They replicate silently with the bacterium until triggered to enter the lytic cycle. Examples include bacteriophage lambda (λ).
Correct answer: C – Retroviruses
This describes the retrovirus replication cycle. Their positive-strand RNA genome is converted to double-stranded DNA by reverse transcriptase, then integrated into the host genome by integrase as a provirus. This is distinct from other positive-strand RNA viruses that use their genome directly as mRNA.
Correct answer: D – Any of these
Congenital CMV is the most common intrauterine infection. It can cause a wide spectrum of damage including mental retardation, sensorineural hearing loss, hepatosplenomegaly (enlarged spleen and liver), microcephaly, and chorioretinitis. Severely affected infants may present with "blueberry muffin" rash due to extramedullary hematopoiesis.
Correct answer: A – Have no capsid protein or envelope
Viroids are the smallest known infectious agents — they consist of a short, circular, single-stranded RNA molecule with no protein coat (capsid) and no envelope whatsoever. They are even smaller than viruses and cause disease primarily in plants (e.g., potato spindle tuber disease).
Correct answer: D – Prions
Prions are misfolded proteins (PrP^Sc) that cause fatal neurodegenerative spongiform encephalopathies. They contain no nucleic acid — making them unique among all known infectious agents. They are extraordinarily resistant to heat, radiation, and standard disinfection. CJD, Kuru, scrapie (sheep), and variant CJD (Mad Cow) are all prion diseases.
Correct answer: D – Epstein-Barr virus
EBV is strongly associated with Burkitt's lymphoma — a B-cell malignancy classically presenting as a jaw tumor in African children. EBV immortalizes B lymphocytes. It is also associated with infectious mononucleosis, nasopharyngeal carcinoma, and Hodgkin's lymphoma.
Correct answer: C – Both A and B
Acute Encephalitis Syndrome (AES) is defined as inflammation of the brain parenchyma, most commonly caused by viral infections (HSV, JE virus, enteroviruses, arboviruses). Both statements are correct — AES is viral-mediated inflammatory brain disease.
Correct answer: E – All the above
AES presents with the classic triad of fever, altered consciousness/confusion, and neurological deficits. Additional symptoms include vomiting, seizures, headache, photophobia, and focal neurological signs depending on the brain region affected.
Correct answer: D – All the above
Management of AES is supportive and includes corticosteroids (to reduce cerebral edema), mechanical ventilation (if respiratory compromise), and anticonvulsants (to control seizures). Acyclovir is added if HSV encephalitis is suspected. ICU-level care is often required.
Correct answer: B – HSV-1 and HSV-2
Genital herpes is caused by both HSV-1 and HSV-2. Historically HSV-2 was the dominant cause, but HSV-1 now accounts for a significant and growing proportion of genital herpes cases, especially in young adults, likely due to orogenital transmission.
Correct answer: C – HSV is readily inactivated by drying and soap and water
HSV is an enveloped virus and is therefore relatively fragile outside the host. It is rapidly inactivated by desiccation (drying), soap, and water — explaining why fomite transmission is rare. Most transmission actually occurs during asymptomatic shedding (making D false).
Correct answer: D – All of the above
All three are nucleoside analogue antivirals active against HSV. Acyclovir is the prototype; Valacyclovir is the oral prodrug of acyclovir with better bioavailability; Famciclovir is the prodrug of penciclovir. All three are used for genital herpes treatment and suppression.
Correct answer: D – She is always at risk for shedding the virus
Once infected with HSV, the virus establishes lifelong latency in sensory ganglia. Viral shedding — both symptomatic and asymptomatic — occurs intermittently for life. There is no cure, and she will always carry transmission risk. Suppressive antiviral therapy (acyclovir/valacyclovir) can reduce but not eliminate shedding.
Correct answer: B – Hepatitis B virus
Hepatitis B virus (HBV) is the only DNA virus among the major hepatitis viruses. It belongs to the Hepadnaviridae family with a partially double-stranded circular DNA genome. HAV is a picornavirus (ssRNA), HCV is a flavivirus (ssRNA), and HDV is a virusoid (negative-sense ssRNA).
Correct answer: B – Nervous system
Poliovirus enters via the fecal-oral route and replicates in the gut, but its primary tropism is the anterior horn motor neurons of the spinal cord. Destruction of these neurons causes the flaccid paralysis characteristic of paralytic poliomyelitis. The virus uses CD155 (PVR) as its receptor on neural cells.
Correct answer: D – Fecal-oral route
HAV is transmitted exclusively by the fecal-oral route — contaminated water, raw shellfish, unwashed produce, and poor hand hygiene. It is a non-enveloped virus, making it resistant to environmental conditions. Unlike HBV/HCV, it is NOT sexually transmitted or bloodborne as a primary route.
Correct answer: D – All of these
HBV is found in blood, semen, vaginal secretions, saliva, breast milk, and other body fluids. Blood has the highest viral concentration. This explains its transmission routes — sexual contact, needlesharing, vertical (mother to child), and rarely saliva (deep kissing, bites).
Correct answer: C – Detection of IgM anti-HAV by ELISA
The gold standard for acute HAV diagnosis is detection of IgM anti-HAV antibodies by ELISA — these appear at onset of symptoms and persist for 3-6 months. Elevated aminotransferases indicate liver injury but are nonspecific. Fecal HAV detection is possible but not the standard diagnostic method.
Correct answer: A – They replicated in the host cell cytoplasm
Herpesviruses are DNA viruses that replicate in the nucleus, NOT the cytoplasm. DNA replication, transcription, and capsid assembly all occur in the nucleus. The virus then acquires its envelope by budding through the nuclear membrane. This distinguishes them from poxviruses, which are the only DNA viruses that replicate in the cytoplasm.