Clinical virology – durable markers: After natural infection, which listed virus leaves markers that are reliably detectable long-term in most individuals, allowing past infection to be identified during adult screening?

Introduction:
Serologic and molecular footprints of prior viral infection vary by virus. In public health and transfusion medicine, certain markers persist and are used to infer previous exposure. This item focuses on the virus for which routine adult screening relies on a durable marker of past infection.

Given Data / Assumptions:

• We compare common human viruses: HBV, HSV, VZV, CMV.
• “Always detectable after infection” is interpreted as a robust, durable laboratory marker in typical adult practice.
• We prioritize markers widely used in clinical screening algorithms.

Concept / Approach:
For hepatitis B virus, anti-HBc (core antibody) of the IgG class usually persists for life after natural infection. Screening panels routinely leverage anti-HBc to establish prior exposure even when HBsAg has cleared and anti-HBs may vary. While herpesviruses also induce long-lived IgG, standardized adult screening for past infection typically emphasizes HBV core antibody as a dependable indicator across populations.

Step-by-Step Solution:
Identify viruses known for lifelong seropositivity. Recall that HBV anti-HBc IgG is a canonical, durable marker used in algorithms. Select the option that matches routine detection of past infection. Therefore choose Hepatitis B virus.

Verification / Alternative check:
Interpretation charts show that anti-HBc positive with HBsAg negative and anti-HBs positive indicates past resolved infection; even if anti-HBs wanes, anti-HBc IgG often remains, flagging prior exposure.

Why Other Options Are Wrong:
Herpes simplex virus – IgG often persists but is not a standard universal screening marker; detection is not uniformly performed to infer past infection.

Varicella–zoster virus – IgG persists, yet adult screening programs commonly vaccinate or use exposure history; not the canonical “always-detectable” marker emphasized in algorithms.

Cytomegalovirus – IgG persistence varies and is context dependent; not the standard marker for broad adult screening outside specific settings.

None – incorrect because HBV provides a robust, lasting serologic footprint.

Common Pitfalls:
Equating “can be detected” with “routinely used marker.” Many infections leave IgG, but HBV anti-HBc is uniquely central to screening pathways.

Final Answer:
Hepatitis B virus.