Virology

Viruses & Virology

Definition of Virus

  • Virus: A type of parasite that can only reproduce inside a host cell.

    • Cannot reproduce independently.

    • Host range: The number of different host cells a virus can infect.

    • Can cause damage or kill host cells through the process of lysis after replicating new viruses.

    • Can kill host cells through the production of toxins.

    • The viral envelope may also contain toxic elements.

Viral Genomes

  • Viral genomes can consist of:

    • Single-stranded DNA or Double-stranded DNA.

    • Single-stranded RNA or Double-stranded RNA.

  • Viruses can be categorized based on their genome type.

Capsid Structure

  • Capsid: The protein shell that encloses the viral genome.

    • Constructed from protein units called capsomers.

Reproduction of Viruses

  • The process of viral reproduction involves:

    • Entry into a host cell where it hijacks the cellular machinery.

    • Utilizes host cell enzymes, ribosomes, tRNAs, and ATP to replicate.

    • The virus self-assembles and ultimately causes the host cell to lyse (break open) to release new viral particles.

Pathology of Viruses

Influenza Virus

  • Influenza: A significant concern, especially the bird flu.

    • Has the ability to jump species, referred to as zoonosis.

    • Often results in severe and infectious outcomes in humans.

Continued Virology Notes

Viral Infection Process

  • Steps in viral infection:

    • Identification of a suitable host by the virus.

    • Commandeering the host cell to produce new viral DNA.

    • Reassembly of new viral particles within the host cell.

    • Lysis of the host cell, which leads to the release of new viruses to infect additional cells.

  • Zoonosis increases virulence and likelihood of pandemics due to:

    • Higher transmission rates among humans.

    • Historical cases such as the influenza pandemic where living in close quarters facilitated spread.

    • The 1918 influenza pandemic is noted as one of the worst, exacerbated by lack of isolation and quick onset of infection.

HIV and AIDS

  • HIV (Human Immunodeficiency Virus): A retrovirus that consists of RNA and is noted for its high mutation rate.

    • Leads to AIDS (Acquired Immunodeficiency Syndrome), which is a condition characterized by a significantly weakened immune system.

    • Antiretroviral treatment such as HAART (Highly Active Antiretroviral Therapy) became available in 1986 and significantly affects the viral load in individuals with HIV.

    • Presents challenges related to genetic barriers in treatment efficacy.

Notable Viral Outbreaks

SARS-CoV and SARS-CoV-2

  • SARS-CoV (Severe Acute Respiratory Syndrome Coronavirus) emerged in 2003.

    • Originated from bats, transitioned to cats, and then to humans.

  • SARS-CoV-2 (causing COVID-19) likely jumped from bats with potential intermediaries such as pangolins or raccoon dogs.

COVID-19 Vaccine and Mortality

  • The effectiveness of COVID-19 vaccines:

    • Studies indicate vaccines can halve mortality rates among infected individuals.

    • Anaphylaxis occurs at an extremely rare rate of approximately 0.5 per million doses administered.

    • Other rare complications reported include thrombosis and Guillain-Barre syndrome.

Exam Content and Preparation

  • Be aware of potential topics related to previous examinations to review and prepare for future assessments.

  • Pay special attention to the historical and modern implications of viral diseases on human health and responses by the medical community.