Virulence and Pathogenicity Flashcards
Pathogenicity
Ability of a virus to cause disease in host
Pathogen
Virus that can cause disease
Pathogenesis
Manner or Mechanisms of development of disease
Virulence
Degree of pathogenicity
Avirulent
Non virulent or no damage to host
Variables related to virus that affect virulence (5)
Genetic variation of virus Route of entry Affinity to organs Dose of infection Immuno Evasion
Variables related to HOST that affect virulence
Species
IS
Host physiological factors such as nutrition, age, etc.
Fever
LD 50
Minimum dose of a virus that can cause death in 50 % of a population
Routes of infection (5)
Skin Mucous Membrane GIT Transcutaneous Infection Respiratory tract
Transcutaneous infections are through
Bites of arthropods, infected animals, or contaminated objects (syringes)
How can a virus spread in host (6)
Local spread on epithelial surfaces To subepithelial invasion and lymphatic spread To bloodstream the all over Disseminated Infection Systemic Infection Via Nerves
Viremia
Presence of virus in blood
Primary Viremia can happen how (2)
From epithelium to blood
Directly injected through bite or syringe
What is primary viremia
initial entry to BLOOD
What does it means that is in 2ry viremia
Virus has replicated and multiplied in major ORGANS and once more entered the circulation
Disseminated infection is
Spread beyond Primary site of infection
Systemic infection
If a number of organs or tissues are infected
Spread through nerves (4)
Peripheral nerves
Receptor neurons in nasal olfactory epithelium
Cross BBB
CNS
Neurotropic virus
Viruses that can infect neural cells
May occur by neural or hematogenous spread
Neuroinvasive
Enter CNS after infection of peripheral site
Neurovirulent
Can cause disease of nervous tissues, manifested by neurological symptoms and often death
Pantropic viruses
Can replicate in more than one host organ tissue
Mechanisms of viral injury (5)
Inhibition of host cell nucleic acid synthesis
Inhibition of host cell RNA synthesis (transcription)
Inhibition of protein synthesis
Cytopathic effects of Toxic viral proteins
Interference with cellular membrane function
What are the outcomes of viral injury (5)
Cell lysis/bursting following virus replication allowing release of new viruses Apoptosis Oncoviruses Persistent infection Immunosuppression
