Pathology 18

• Viruses possess genetic information in DNA or RNA and lack the machinery necessary to create progeny.
• Viruses are unable to generate energy or substrate as they lack organelles, ribosomes, and mitochondria.
• Viruses can only replicate in living host cells and do not undergo binary fission or mitosis during replication.
• Viruses are the smallest infectious agents, ranging from 20 nm to 300 nm in size.
• Human viruses have a relative size of 5.
• Viruses have a structure consisting of a virus particle or virion, genetic material, capsid, nucleocapsid, and envelope.
• Viruses can contain either DNA or RNA as their genetic material, which can be single-stranded or double-stranded.
• The capsid is a protein coat that surrounds and protects the viral genetic material, composed of repeating protein subunits called capsomers.
• Some viruses have an outer lipid envelope derived from the host cell membrane, studded with viral glycoproteins and referred to as enveloped viruses.
• Not all viruses have an envelope; those lacking it are referred to as naked viruses.
• Viral glycoproteins are proteins with attached carbohydrate molecules, often found on the surface of the viral envelope or capsid and play a crucial role in viral attachment to host cells.
• Enveloped viruses may have matrix proteins located beneath the viral envelope, which help anchor the envelope to the capsid.
• Herpes simplex virus (HSV) can be transmitted through direct contact with infected skin or mucous membranes.
• The complement system, a group of proteins in the blood, can help in the destruction of viruses directly or enhance the effectiveness of antibodies.
• The common cold virus (rhinovirus) can be transmitted through direct contact with respiratory secretions or contaminated surfaces.
• Airborne is a route of transmission for measles.
• Ingestion is a route of transmission for rotavirus and norovirus, causing gastroenteritis.
• Rabies and Dengue are examples of zoonotic diseases.
• Cytomegalovirus (CMV) can cause congenital infection.
• Human Immunodeficiency Virus (HIV) can be transmitted from an infected mother to her child during childbirth or through breastfeeding.
• Droplets are a route of transmission for influenza virus and SARS-CoV-2, the virus responsible for COVID-19.
• Hepatitis B virus (HBV) and Hepatitis C virus (HCV) can be transmitted through blood, sexual fluids (Sexually transmitted disease), and breast milk.
• Some viruses have spikes or fibers protruding from the capsid or envelope, involved in attaching the virus to host cells.
• Viruses are classified based on their type of genetic material, structure and symmetry, and other characteristics.
• Memory immune response persists after the infection is resolved, allowing for a quicker and more effective response upon re-exposure.
• Varicella-zoster virus (VZV) causes chickenpox initially and can later reactivate to cause shingles.
• The adaptive immune response is more specific and takes a bit longer to develop, involving T cells and B cells.
• The host immune response toward viral infection involves the recognition of viral components, such as viral proteins or nucleic acids, and can involve the innate immune response, adaptive immune response, and memory immune response.
• Phagocytosis is a process where immune cells such as macrophages and dendritic cells can engulf and digest virus particles or infected cells.
• Oncogenic viruses activate oncogenes to transform normal cells into cancerous cells.
• Herpesvirus replication stops in the host cell cytoplasm, resulting in latency.
• The innate immune response is immediate, non-specific, and involves interferons and natural killer (NK) cells.
• Cancer-inducing viruses include Human T lymphotropic virus 1 & 2, Epstein-Barr virus (EBV), Papillomaviruses (HPV 16 & 18), Hepatitis B and C virus.
• Excessive cytokine production, known as a cytokine storm, can contribute to severe inflammation and tissue damage in some viral infections.
• Retroviruses use reverse transcriptase to enter the nucleus, integrate into the host genome, and are transcribed by the host polymerase.
• Paramyxovirus, Orthomyxovirus, Rhabdovirus, Picornavirus, Togavirus, Flavivirus, Herpesvirus, Adenovirus, Hepadnavirus, Parvovirus are examples of viruses that use ssRNA(+) as their genome.
• Cytokines are signaling molecules produced by immune cells that regulate the immune response.
• New viral particles are assembled from the synthesized viral genetic material and proteins.
• Viruses can also be classified based on their envelope composition, structure, and the presence of a viral attachment protein (VAP).
• Viruses can be classified based on the genetic content into DNA Viruses and RNA Viruses.