Medical virology fundamentals: Which of the following human diseases is caused by a DNA virus (select the single best answer)?

Introduction / Context:
Viruses are broadly grouped by genome type into DNA and RNA viruses. Many high-yield exam questions test whether you can quickly match common diseases to their genome class. Knowing this helps with understanding replication sites, mutation rates, and vaccine strategies.

Given Data / Assumptions:

• We compare familiar infections: polio, yellow fever, measles, smallpox, and influenza.
• Only one listed disease is caused by a DNA virus.
• We assume standard modern taxonomic assignments.

Concept / Approach:
Smallpox is caused by Variola virus, a large double-stranded DNA virus in the Poxviridae family. In contrast, poliomyelitis (Picornaviridae), yellow fever (Flaviviridae), measles (Paramyxoviridae), and influenza (Orthomyxoviridae) are all RNA viruses. Therefore, smallpox is the single correct DNA-virus disease among the options.

Step-by-Step Solution:
List genome classes for each disease agent. Identify the only dsDNA agent: Variola virus (smallpox). Confirm all other listed diseases are caused by RNA viruses. Select “Smallpox.”

Verification / Alternative check:
Key medical microbiology texts categorize Poxviridae as DNA viruses that replicate in the cytoplasm, whereas the others are RNA viruses with different replication strategies.

Why Other Options Are Wrong:

• Poliomyelitis: Caused by poliovirus, a positive-sense RNA virus.
• Yellow fever: Caused by yellow fever virus, a positive-sense RNA flavivirus.
• Measles: Caused by measles virus, a negative-sense RNA paramyxovirus.
• Influenza: Caused by segmented negative-sense RNA orthomyxoviruses.

Common Pitfalls:
Assuming “ancient” diseases are DNA-based; genome type is independent of historical prevalence.

Final Answer:
Smallpox is caused by a DNA virus (Variola virus).