Enveloped hepatitis viruses: All of the following are enveloped except which virus?

Introduction:
The presence or absence of a lipid envelope influences environmental stability, transmission route, and resistance to disinfectants. Among hepatotropic viruses, envelope status is a high-yield identification point.

Given Data / Assumptions:

• We must pick the non-enveloped virus among listed hepatitis viruses.
• HAV and HEV typically spread fecal–oral; HBV, HCV, and HDV spread mainly via blood and body fluids.

Concept / Approach:
HAV is a non-enveloped, positive-sense RNA virus in the Picornaviridae family (genus Hepatovirus), conferring environmental resilience. HBV (Hepadnaviridae), HCV (Flaviviridae), and HDV (a defective RNA agent requiring HBV) are enveloped. HEV is non-enveloped in stool but can be quasi-enveloped in blood; however, the classic exam contrast focuses on HAV as the archetypal non-enveloped member among the choices.

Step-by-Step Solution:
List envelope status for each hepatitis virus. Identify HAV as classically non-enveloped and environmentally hardy. Select HAV as the exception among enveloped viruses.

Verification / Alternative check:
Textbook virology differentiates enteric non-enveloped HAV from blood-borne enveloped HBV, HCV, and HDV.

Why Other Options Are Wrong:

• HBV / HCV / HDV: Enveloped viruses transmitted parenterally and via body fluids.
• HEV: Often considered non-enveloped in stool; some curricula may not include it in the classic list; the most consistent single best answer here is HAV.

Common Pitfalls:
Overlooking special quasi-envelope forms of HEV in blood; for standard MCQ framing, HAV is the clear non-enveloped pick.

Final Answer:
Hepatitis A virus (HAV) is not enveloped.