Human Viral Diseases - Prepared Notes

Major Criteria for Virus Classification

  • Type of genomic nucleic acid
    • DNA or RNA
  • Nucleic acid strandedness
    • Double-stranded (ds) or single-stranded (ss), partially ds
  • Sense of ss nucleic acid
    • Positive (+), negative (-), or ambisense
  • Capsid morphology
    • Icosahedral, helical, or complex
  • Envelope presence
    • Present or absent
  • Genome segmentation
    • Number of segments in genome
  • Genomic structure
    • Specific properties, such as type of RNA cap or location of structural genes
  • Electron micrographic (EM) appearance
    • Visual characteristics under electron microscope
  • Size of virion and/or genome
    • Varies between different families

Classification of Human Virus Families

  • Adenoviridae: dsDNA, 1 segment, Icosahedral, Naked
  • Anelloviridae: ssDNA (-), 1 segment, Icosahedral, Naked
  • Arenaviridae: ssRNA (-), 2 segments, Helical, Enveloped
  • Astroviridae: ssRNA (+), 1 segment, Icosahedral, Naked
  • Caliciviridae: ssRNA (+), 1 segment, Icosahedral, Naked
  • Coronaviridae: ssRNA (+), 1 segment, Helical, Enveloped
  • Filoviridae: ssRNA (-), 1 segment, Helical, Enveloped
  • Flaviviridae: ssRNA (+), 1 segment, Icosahedral, Enveloped
  • Hepadnaviridae: Partially ssDNA, 1 segment, Icosahedral, Enveloped
  • Herpesviridae: dsDNA, 1 segment, Icosahedral, Enveloped
  • Orthomyxoviridae: ssRNA (-), 6-8 segments, Helical, Enveloped

Common Routes of Virus Transmission to Humans

  • Respiratory route: Droplets and aerosols; viruses include influenza virus, varicella-zoster virus, etc.
  • Faecal-oral route: Involves polioviruses, hepatitis A virus, rotavirus, etc.
    • Poliomyelitis: Can lead to serious disease including paralysis.
    • Coxsackieviruses: Cause HFMD, herpangina, myocarditis, and meningitis.
    • Hepatitis A: Liver infection causing jaundice, fatigue.
    • Rotavirus: Causes gastroenteritis.
    • Norovirus: Known for severe vomiting, diarrhea.

Direct Contact Infections

  • HPV (Human Papillomavirus): Genital and common warts; high-risk strains cause various cancers.
  • HSV-1 (Herpes Simplex Virus Type 1): Oral herpes, genital herpes, and other infections.

Sexual Contact Infections

  • HIV-1: Leads to AIDS; prevention through safe practices and ART.
  • HTLV-1: Often asymptomatic; can cause severe complications.
  • HBV (Hepatitis B): Causes chronic infection leading to liver issues; prevention through vaccination.

Urine-Associated Virus Infections

  • CMV (Cytomegalovirus): Spreads through body fluids; can cause severe symptoms in immunocompromised individuals. Congenital CMV can lead to significant health issues in newborns.

Animal-Borne Infections

  • Rabies: Zoonotic; presents with neurological symptoms; prevention through vaccination and immediate treatment post-exposure.

Arthropod-Borne Viruses

  • Dengue: High fever, severe headache; prevention focuses on mosquito bite avoidance.
  • Yellow Fever: Can lead to severe complications; vaccination recommended.
  • Zika Virus: Linked to congenital malformations; prevention includes mosquito bite avoidance.

Rodent-Associated Transmission

  • Hantavirus: Can lead to HPS (Hantavirus Pulmonary Syndrome) and HFRS (Haemorrhagic Fever with Renal Syndrome); both life-threatening if untreated.

Bat-Associated Viruses

  • Nippah virus: Transmission through bats and pigs; leads to severe respiratory illness and neurological issues.

Further Reading

  • Resources for detailed information available via online academic articles and health organizations.