Clinically Important RNA Viruses Overview

Clinically Important RNA Viruses

• RNA viruses are classified into various families based on envelope presence, capsid symmetry, RNA structure, and clinical significance.
• Key RNA virus families include Reoviruses, Picornaviruses, Caliciviruses, Flaviviruses, Togaviruses, Retroviruses, Coronaviruses, Orthomyxoviruses, Paramyxoviruses, Rhabdoviruses, Filoviruses, Arenaviruses, and Bunyaviruses.

Virus Families Overview

• Reoviruses: Non-enveloped, icosahedral, double-stranded RNA. Notable for causing diarrhea in infants (Rotavirus).
• Picornaviruses: Non-enveloped, linear single-stranded RNA. Includes poliovirus (aseptic meningitis) and rhinoviruses (common cold).
• Caliciviruses: Non-enveloped, single-stranded RNA. Major pathogen is Norovirus, linked to gastroenteritis.
• Flaviviruses: Enveloped, single-stranded RNA. Key viruses include Hepatitis C, Yellow fever, and Zika virus, often transmitted by arthropods.
• Togaviruses: Enveloped, single-stranded RNA. Notable for Rubella virus and encephalitis viruses.
• Retroviruses: Enveloped, single-stranded RNA that reverse transcribes into DNA. Key virus is HIV, responsible for AIDS.
• Coronaviruses: Enveloped, single-stranded RNA. Include mild cold viruses and severe pathogens like SARS-CoV-2, leading to respiratory disease.
• Orthomyxoviruses: Enveloped, segmented negative-sense RNA. Includes influenza viruses that can undergo genetic reassortment.
• Paramyxoviruses: Enveloped, non-segmented negative-sense RNA. Includes pathogens like Measles, Mumps, and Respiratory Syncytial Virus (RSV).
• Rhabdoviruses: Enveloped, negative-sense RNA. Key pathogen is Rabies virus, characterized by bullet-shaped morphology.
• Filoviruses: Enveloped, negative-sense RNA. Include Ebola and Marburg viruses, requiring high containment for study.
• Arenaviruses: Pleomorphic, enveloped viruses with ambisense RNA. Include Lymphocytic choriomeningitis virus and Lassa virus.

Replication and Maturation Strategies

• RNA viruses can be categorized based on their genomic RNA structure and replication strategies, affecting how they synthesize proteins and mature.
• Positive-strand viruses: Include Picornaviridae, Togaviridae, Retroviridae. Genomic RNA is infectious and acts as mRNA.
• Negative-strand viruses: Include Orthomyxoviridae, Paramyxoviridae, Rhabdoviridae. Require viral enzymes to transcribe RNA.
• Replication cycle: Varies among families, affecting total time for maturation and site of genome replication (cytoplasm or nucleus). Example: Picornaviridae (6-8 hours) versus Orthomyxoviridae (15-30 hours).

Key Clinical Symptoms Associated with Viruses

• Rotavirus: Diarrhea in infants.
• Poliovirus: Aseptic meningitis, flaccid paralysis.
• Rhinovirus: Common cold.
• Hepatitis A & E: Hepatitis.
• Norovirus: Gastroenteritis.
• Yellow fever: Fever, nausea, jaundice.
• HIV: AIDS.
• Influenza virus: Flu and associated complications.
• Measles: Cough, cold, conjunctivitis, rash.
• Rabies virus: Fever, agitation, hydrophobia.

Conclusion

• Understanding the classification, replication mechanisms, and clinical implications of RNA viruses is crucial for diagnostics and treatment of viral infections.

This quiz explores the various families of clinically important RNA viruses, detailing their characteristics and clinical significance. Topics include Reoviruses, Picornaviruses, Caliciviruses, and more. Test your knowledge on the structure, transmission, and diseases caused by these viruses.