Viral Life Cycle and Disease Practice Questions
20 free Viral Life Cycle and Disease practice questions for the USMLE Step 1. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
A patient develops fever and rash after a trip to the Caribbean. RT-PCR confirms dengue virus. Which viral genus does dengue belong to?
- A Picornavirus
- B Flavivirus
- C Adenovirus
- D Paramyxovirus
Correct answer: Flavivirus
Dengue virus is a flavivirus, an enveloped, positive-sense single-stranded RNA virus in the family Flaviviridae, alongside Zika, yellow fever, West Nile and Japanese encephalitis viruses. It is transmitted by Aedes aegypti and Aedes albopictus mosquitoes and has four serotypes, which is why a second infection with a different serotype carries the highest risk of severe dengue.
HIV requires which enzyme to convert viral RNA into DNA?
- A RNA polymerase II
- B Reverse transcriptase
- C DNA polymerase I
- D Integrase
Correct answer: Reverse transcriptase
Reverse transcriptase converts HIV RNA into complementary DNA, enabling integration into the host genome.
A patient with a history of bone marrow transplant develops pneumonia from CMV reactivation. What type of virus is CMV?
- A Enveloped dsDNA herpesvirus
- B Non-enveloped ssRNA virus
- C Enveloped negative-sense RNA virus
- D Segmented dsRNA virus
Correct answer: Enveloped dsDNA herpesvirus
CMV is a herpesvirus, which are enveloped, double-stranded DNA viruses. They are known for latent infections with reactivation.
Influenza virus requires which process to produce infectious progeny due to its segmented genome?
- A Antigenic drift
- B Antigenic shift
- C Frameshift mutation
- D Rolling-circle replication
Correct answer: Antigenic shift
Antigenic shift results from reassortment of influenza's segmented RNA genome. This leads to major antigenic changes and pandemics.
A patient develops muscle paralysis due to poliovirus. Which receptor does poliovirus use for entry?
- A CD155 (PVR)
- B CD55 (DAF)
- C CD4
- D CCR5
Correct answer: CD155 (PVR)
Poliovirus binds CD155 (also called PVR or Necl-5) on host cells. It is a picornavirus that spreads through the GI tract.
A man develops jaundice and dark urine 6 months after acute viral hepatitis. Which hepatitis virus is most likely to cause chronic infection?
- A Hepatitis A
- B Hepatitis C
- C Hepatitis E
- D Hepatitis D alone
Correct answer: Hepatitis C
Hepatitis C frequently progresses to chronic infection due to its high mutation rate and ability to evade immunity.
A patient with parotitis also develops orchitis. Which virus is most likely responsible?
- A Measles virus
- B Mumps virus
- C Rubella virus
- D Adenovirus
Correct answer: Mumps virus
Mumps virus, a paramyxovirus, causes parotitis and can lead to orchitis in males.
A patient with rabies shows eosinophilic intracytoplasmic inclusions in neurons. What are these inclusions called?
- A Councilman bodies
- B Löwy bodies
- C Negri bodies
- D Guarnieri bodies
Correct answer: Negri bodies
Negri bodies are cytoplasmic inclusions found in neurons infected with rabies virus. They are diagnostic on histology.
A patient infected with HPV-16 develops cervical intraepithelial neoplasia. Which viral proteins inactivate tumor suppressors?
- A E1 and E2
- B E5 and E7
- C E6 and E7
- D E3 and E4
Correct answer: E6 and E7
HPV E6 inhibits p53 and E7 inhibits Rb, promoting uncontrolled cell division and carcinogenesis.
Rotavirus infection causes severe diarrhea by which mechanism?
- A Enterotoxin overproduction
- B Villous atrophy
- C NSP4-mediated chloride loss
- D Invasion of intestinal mucosa
Correct answer: NSP4-mediated chloride loss
Rotavirus NSP4 acts as an enterotoxin causing chloride and water loss. It also causes villous shortening.
Herpes simplex virus remains latent in which location?
- A Dorsal root ganglia
- B Red bone marrow
- C Regional lymph nodes
- D Hepatic sinusoids
Correct answer: Dorsal root ganglia
HSV establishes latency in sensory ganglia such as the trigeminal and sacral ganglia. Reactivation causes recurrent lesions.
A man develops severe watery diarrhea after a cruise. Stool PCR detects Norovirus. What is the genome of this virus?
- A Enveloped double-stranded DNA
- B Non-enveloped positive-sense RNA
- C Enveloped negative-sense RNA
- D Segmented double-stranded RNA
Correct answer: Non-enveloped positive-sense RNA
Norovirus is a non-enveloped, positive-sense RNA virus commonly associated with outbreaks on cruise ships.
A patient with roseola (HHV-6) presents with high fever followed by a rash. Which cells does the virus primarily infect?
- A Neutrophils
- B CD4+ T cells
- C Hepatocytes
- D Endothelial cells
Correct answer: CD4+ T cells
HHV-6 infects CD4+ T cells. It causes exanthem subitum (roseola) in infants.
A man returns from Africa with hemorrhagic fever caused by Ebola virus. To which viral family does Ebola belong?
- A Filovirus
- B Flavivirus
- C Togavirus
- D Orthomyxovirus
Correct answer: Filovirus
Ebola is a filovirus, an enveloped negative-sense RNA virus known for causing severe hemorrhagic fever.
A newborn exposed to rubella in utero develops congenital cataracts. What property of rubella enables transplacental infection?
- A Segmented RNA genome
- B Viremia in the mother
- C Cytoplasmic replication
- D Reverse transcription
Correct answer: Viremia in the mother
Rubella causes maternal viremia, allowing the virus to cross the placenta and infect the fetus.
A patient with hepatitis B shows ground-glass hepatocytes. Which component of HBV accumulates in hepatocytes?
- A HBcAg
- B HBeAg
- C HBsAg
- D HBxAg
Correct answer: HBsAg
Ground-glass hepatocytes result from accumulation of HBsAg (surface antigen) within the endoplasmic reticulum of infected hepatocytes.
A patient with vesicular rash on the trunk is diagnosed with varicella-zoster virus. Where does VZV establish latency?
- A Enteric neurons
- B Dorsal root ganglia
- C Corticospinal neurons
- D Retinal ganglion cells
Correct answer: Dorsal root ganglia
VZV remains latent in dorsal root or trigeminal ganglia. Reactivation causes shingles.
A patient with viral meningitis is found to have an enterovirus infection. Which virus is most likely responsible?
- A Coxsackievirus
- B Adenovirus
- C Herpes simplex virus
- D Rabies virus
Correct answer: Coxsackievirus
Coxsackievirus, a picornavirus, is a common cause of viral meningitis, especially in children.
A patient with hepatitis D infection becomes severely ill after acquiring HBV simultaneously. What term describes this situation?
- A Reactivation
- B Superinfection
- C Coinfection
- D Antigenic shift
Correct answer: Coinfection
Coinfection occurs when both HBV and HDV are acquired at the same time. It is typically less severe than superinfection.
An infant with laryngotracheobronchitis (croup) presents with a barking cough and inspiratory stridor. Which virus is the most likely cause?
- A Respiratory syncytial virus
- B Parainfluenza virus
- C Rhinovirus
- D Adenovirus
Correct answer: Parainfluenza virus
Parainfluenza virus, a paramyxovirus, is the classic cause of croup. It leads to subglottic swelling and the characteristic barking cough.