MLT GlobeVirology: Herpesviruses
36 Virology MCQs on Herpesviruses with answers and explanations.
A teenager with fever, pharyngitis, cervical lymphadenopathy and atypical lymphocytes has a positive heterophile antibody (monospot) test. The diagnosis is:
The monospot detects heterophile antibodies that agglutinate horse red cells, produced in EBV infectious mononucleosis.
A virus hides silently in sensory ganglion neurons for decades and later reactivates. Which virus family behaves this way?
Alphaherpesviruses (HSV, VZV) establish lifelong latency in sensory ganglia and reactivate as cold sores or shingles. Toga-, picorna- and orthomyxoviruses cause acute infections.
Which statement about varicella and herpes zoster is NOT true?
Varicella is a generalised vesicular rash of primary infection; zoster is a painful dermatomal eruption from reactivated VZV, usually in older or immunosuppressed people.
Which statement about infectious mononucleosis is correct?
Classic mononucleosis is EBV infection, typically in adolescents, with heterophil antibodies and atypical lymphocytes. Treatment is supportive.
A 10-day-old infant has fever, seizures and CSF pleocytosis; herpes simplex encephalitis is suspected. Which test on CSF is most sensitive?
CSF PCR detects HSV DNA with high sensitivity and specificity and is the test of choice. HSV culture of CSF is rarely positive, and IgG may be maternal.
Which infection most characteristically produces many reactive (atypical) lymphocytes on the blood film?
EBV-infected B cells trigger a large CD8 T-cell response seen as atypical (Downey) lymphocytes, often >10% of leukocytes.
Which lesion is classically caused by herpes simplex virus type 1 rather than type 2?
HSV-1 classically causes oral and facial lesions and adult encephalitis; HSV-2 mainly genital and neonatal infection. Zoster is VZV reactivation.
Which virus is the most common infectious cause of congenital malformations and sensorineural hearing loss?
Congenital CMV affects about 0.5-1% of live births and is the leading non-genetic cause of hearing loss.
Which drug is the treatment of choice for herpes simplex infections such as encephalitis or severe genital herpes?
Acyclovir is phosphorylated by viral thymidine kinase and inhibits HSV DNA polymerase. Azithromycin is antibacterial; amantadine and oseltamivir act on influenza.
A child has a very itchy rash with crops of vesicles at different stages on the trunk and face. Which virus causes chickenpox?
Chickenpox is primary VZV infection; lesions in various stages (papules, vesicles, crusts) are typical. Later reactivation causes zoster.
A student has malaise, fatigue, sore throat, many atypical lymphocytes and a positive heterophil antibody test. What is the likely cause?
A positive heterophil (Monospot/Paul-Bunnell) test with atypical lymphocytosis indicates EBV mononucleosis. Toxoplasma and CMV give heterophil-negative illness.
A patient has a painful vesicular eruption along one thoracic dermatome. Which specimen best confirms varicella-zoster virus?
Unroofing a fresh vesicle and swabbing its base gives cells and fluid rich in virus for PCR or DFA; PCR is now the method of choice.
Large cells with 'owl's eye' intranuclear inclusions in a lung biopsy of a transplant patient suggest infection with:
CMV causes cell enlargement (cytomegaly) with large intranuclear inclusions surrounded by a clear halo. Adenovirus inclusions are smudgy and lack this pattern.
Roseola infantum (sixth disease), with high fever followed by a rash as the fever falls, is caused by:
HHV-6 (and sometimes HHV-7) causes roseola in infants; parvovirus B19 causes fifth disease.
Which statement about the human herpesviruses is NOT true?
EBV and CMV usually cause mononucleosis-like illness without vesicles; only HSV and VZV typically cause vesicles. All eight human herpesviruses are enveloped dsDNA viruses that become latent.
After primary gingivostomatitis, where does herpes simplex virus type 1 usually remain latent?
HSV-1 travels up sensory nerves and becomes latent in the trigeminal ganglion, reactivating as cold sores. EBV, not HSV, is latent in B cells.
Infectious mononucleosis is suspected in a teenager. Which investigation is NOT practical for routine diagnosis?
EBV cannot be grown in routine cell culture. Diagnosis uses heterophil antibodies and EBV-specific serology (VCA IgM/IgG, EBNA).
A newborn has suspected congenital cytomegalovirus infection. Which test on which specimen, collected within the first 3 weeks, is now the method of choice?
Neonates shed CMV heavily in urine and saliva; PCR within 21 days of birth is sensitive and distinguishes congenital from later infection. IgG may be maternal.
Which statement about cytomegalovirus infection is NOT true?
CMV is carried in leukocytes (monocytes, neutrophils), not erythrocytes; this is why leukoreduced blood lowers transfusion risk. It causes retinitis, reactivates and crosses the placenta.
Which statement best describes herpes simplex virus infection?
HSV remains latent in sensory ganglia and reactivates with triggers such as UV light, fever or emotional stress, despite circulating antibodies. Visceral or CNS disease is uncommon.