Which of the following viruses are not RNA viruses: HAV, Influenza virus, HCV, Lassa virus, Smallpox, Adenovirus?

RNA Viruses vs DNA Viruses

Smallpox and Adenovirus are the only DNA viruses in the list; all others (HAV, Influenza virus, HCV, and Lassa virus) are RNA viruses.

Classification of Viruses by Nucleic Acid Type

RNA Viruses (from the list)

1. HAV (Hepatitis A Virus)

   • HAV is an enteric picornavirus with a single-stranded RNA genome of positive-strand polarity, approximately 7478 bases in length 1.
   • It belongs to the Picornaviridae family and is transmitted via the fecal-oral route 2.

2. Influenza Virus

   • Influenza is a non-segmented positive-strand RNA virus 2.
   • It is primarily transmitted from person to person through respiratory droplets when infected individuals cough, sneeze, or talk 2.
   • Influenza viruses can cause significant cardiovascular complications in addition to respiratory disease 3.

3. HCV (Hepatitis C Virus)

   • HCV is an RNA virus with a genome length of approximately 9,600 kilobases 2.
   • It belongs to the Flaviviridae family and is a major cause of chronic liver disease worldwide 2.
   • HCV RNA can be detected in infected individuals using qualitative or quantitative tests 2.

4. Lassa Virus

   • Lassa virus is an enveloped virus containing two single-stranded RNA genome segments 4.
   • It is the causative agent of Lassa fever, a hemorrhagic fever endemic in West Africa 4.
   • Lassa virus is one of the viral hemorrhagic fevers for which ribavirin has been approved as treatment 5.

DNA Viruses (from the list)

1. Smallpox (Variola Virus)

   • Smallpox virus belongs to the Poxviridae family, which are large, complex DNA viruses.
   • It has been eradicated globally through vaccination campaigns but remains a potential bioterrorism agent 6.

2. Adenovirus

   • Adenoviruses are non-enveloped, double-stranded DNA viruses.
   • They can cause respiratory, gastrointestinal, and ocular infections.

Key Distinctions Between RNA and DNA Viruses

RNA viruses generally have higher mutation rates compared to DNA viruses due to the lack of proofreading mechanisms in RNA polymerases. This contributes to their ability to evolve rapidly and potentially evade host immune responses.

DNA viruses typically have more stable genomes and often establish persistent or latent infections. They generally encode more proteins than RNA viruses due to their larger genome size.

Clinical Relevance

Understanding the genetic material of viruses is crucial for:

1. Developing appropriate diagnostic tests (PCR for DNA viruses vs. RT-PCR for RNA viruses)
2. Designing targeted antiviral therapies
3. Understanding patterns of viral evolution and drug resistance

For hepatotropic viruses specifically, HAV and HCV are RNA viruses, while hepatitis B virus (HBV) is a DNA virus that replicates via an RNA intermediate using reverse transcriptase 2, 1.