Recording-2025-03-16T20:30:07.628Z Lecture 13.5

Viral Genomes

• Types of Viral Genomes

  • Viruses can have either DNA or RNA genomes, typically only one or the other.

  • Rare exceptions of viruses with both types exist.

• DNA Genomes

  • Can be further classified into:

    • Double-Stranded DNA (DS)

      • Examples include:

        • Herpesviridae:

          • Example: Chickenpox virus (Varicella virus)

          • Characteristic: Double-stranded DNA virus.

        • Papillomaviridae:

          • Example: Human Papillomavirus (HPV)

          • Key Points:

            • Causes warts and cervical cancer.

            • Vaccination recommended for pre-sexually active individuals.

        • Adenoviridae:

          • Example: Mast adenovirus

          • Key Use: Common cold infections.

        • Hepadnaviridae:

          • Unique structure: Part single-stranded and part double-stranded DNA.

          • Example: Hepatitis B virus (HBV).

    • Single-Stranded DNA (SS)

      • Rare; notably includes parvoviruses, which can cause childhood rashes.

RNA Genomes

• General Characteristics

  • Primarily consist of single-stranded RNA (SS).

  • RNA viruses can be categorized as plus or minus sense:

    • Plus-Strand RNA:

      • Functions as mRNA and is ready for translation upon entering host cells.

      • Examples:

        • Picornaviridae:

          • Example: Poliovirus, Hepatitis A virus.

        • Caliciviridae:

          • Example: Norovirus (leading cause of foodborne illness).

        • Flaviviridae:

          • Example: Yellow fever virus, Hepatitis C virus.

        • Retroviridae:

          • Example: HIV (Human Immunodeficiency Virus).

    • Negative-Strand RNA:

      • Must be converted to positive sense before translation can occur.

      • Examples:

        • Paramyxoviridae:

          • Example: Measles virus.

          • Notable impact: Leading cause of infectious death in some regions.

        • Filoviridae:

          • Example: Ebola virus, known for high fatality rates in outbreaks.

        • Orthomyxoviridae:

          • Example: Influenza virus (concern for potential pandemics).

        • Reoviridae:

          • Only group classified as double-stranded RNA.

          • Example: Rotavirus, a significant childhood illness leading to diarrhea.

Key Notes on Disease Impact

• Hepatitis: Inflammation of the liver caused by various viruses, with different strains across viral families.

• Common Cold: Broadly categorized as upper respiratory infection with numerous causes; adenoviruses are one contributor.

• Norovirus: Frequently causes outbreaks in confined settings; symptomatically leads to gastroenteritis.

• Measles: Serious infectious disease, previously prevalent; nutritional status can affect disease severity.

• Influenza: Historical pandemic potential, with monitoring and vaccines pivotal for public health.