From slides Flashcards
three requirements to ensure infection
- Sufficient infectious particles
- Accessible, permissive and susceptible
- Absent, quiesient or limited antiviral defense
Routes of viral entry into a host
Respiratory Tract Alimentary or Gastrointestinal Tract The urogenital tract The Conjunctiva Skin Trans-placential or perinatal
Viral spread
localized, disseminated, systemic
IFN (interfearon response)
Cytokines that induce ISGs, cause physiological changes Interfearons inhibit viral replication through ISGs
Patterns of infection
Acute (influenza), Peristient ( HIV), Latent (Herpes), Chronic (hepatitis)
Quasispecies
non identical virus in population, lots of sequence mutants in virus.
Drivers of viral evolution
- mutation and selection
- large number of progeny
- selection: host antiviral
- large number of mutants
- Quasispecies effect
Red queen conflict:
constantly mutate to beat virus but they have to be mutating to beat us. Arms race btwn us and virus
ex: TRIM5a change in HIV, PKR change in pox, hepatitis, influenza
constraints of viral evolution
- extreme mutants do not survive
- metastability of capsid
- selection
- genome is only so big
The forces that drive viral emergence is:
- Human population / social behavior (travel)
- Climate changes and environmental changes
- Ecological factors
- Genetic and biological factors
- Microbial evolution / adaptation
Stable
Both virus and host survive and multiply. Some are permanent.
Ex: herpes, cold, flu, measels, HPV
Evolving
instability and unpredictability. May be benign or fatal.
ex: HIV, small pox, west nile
Dead-end
frequent cross-species infection, new host may not spread it, contribute little to the spread of the natural infection
Ex: west nile
Resistant
viral infection is blocked
WNV
emerging, flavivirus via mosquitos
Zika
neurotropic, mosquitos mother to child
yellow fever
mosquitos, jefferson
Nipah
mylasia 1998, from bats urine and human to human, emerging virus
hanta virus
mouse in yosemite
SARS
pneumonia like symptoms mechanical ventilation, emerging virus , og from china doctor
MERS-coV
corona virus,
Mayaro virus
mosquitos, fever aches pain, from earthquake
Ebola Virus
mucosal membranes, immune mediated, infected macrophages, loss of blood flow leads to organ failure.
BSL-4
highest mortality
