Star-shaped enteric virus — Which virus appears star-like under electron microscopy and is transmitted via the fecal–oral route?

Introduction / Context:
Electron microscopy historically aided in distinguishing small, non-enveloped enteric viruses. Morphology plus transmission route can help identify likely pathogens in gastroenteritis outbreaks.

Given Data / Assumptions:

• “Star-shaped” refers to a characteristic surface pattern seen in astroviruses.
• Transmission for these small enteric viruses is predominantly fecal–oral, often through contaminated food, water, or fomites.
• Caliciviruses (e.g., norovirus) have distinct morphology; hepatitis E is a separate enteric hepatitis agent with different imaging features; hepatitis D depends on hepatitis B and is parenteral/sexual.

Concept / Approach:
Astroviruses are named from “astron” (star) due to their 5- to 6-pointed star-like appearance on EM after negative staining. They are recognized causes of pediatric diarrhea and institutional outbreaks.

Step-by-Step Solution:

Verification / Alternative check:
Molecular diagnostics (RT-PCR) corroborate EM findings in epidemiologic investigations of diarrheal disease.

Why Other Options Are Wrong:

• Calicivirus (norovirus): not star-shaped; EM shows distinct cup-like depressions.
• Hepatitis E virus: enterically transmitted but not star-shaped; causes hepatitis rather than classic short-incubation gastroenteritis.
• Hepatitis D virus: requires HBV and spreads mainly via blood/sexual routes.

Common Pitfalls:
Confusing different small RNA enteric viruses based solely on size; morphology and clinical syndromes provide helpful clues.

Final Answer:
Astrovirus