Patterns of Viral Infections Flashcards
Name the transmission routes of viruses
skin, respiratory, faecal-oral, blood, sexual contact, maternal-neonatal, germline, iatrogenic (contaminated needles), nosocomial (HAI)
how do viruses disseminate from the entry site
local infection, apical release, dissemination, basal release, systemic, haematogenous or neural spread
local infection, primary viraemia, amplifies, secondary viraemia, target organ
define tropism
the predilection of viruses to infect certain tissues and not others
what is tropism based on?
susceptibility - receptor interactions
permissivity - ability to use host cell to complete replication
accessibility - ability of virus to reach tissue
list the patterns of viral infection and give characteristics of each
- acute infection followed by clearance = asymptomatic, antigenic variation
- acute infection but accidental tissue infected with permanent damage
- persistent infection = chronic has low replication levels in tissue that regenerate, latent = viral genomes maintained but no virus seen until reactivation when immunity is low
- oncogenensis
summarise viral persistence strategies
evade immune surveillance by downregulating MHC
infect tissue with reduced immune surveillance
CTL escape by mutation
what affects infection outcome?
viral sequence, virus load, host immune response, host comorbidity, confection, meds, host genetics/age/gender
how does viral sequence affect infection outcome?
two staring of same virus differ by single mutation that means one if a vaccine and the other is pathogenic
how does viral load affect infection outcome?
first person in family to be infected has mild case whilst second is more severe due to close contact and higher infectious dose
how do co-infections affect infection outcome?
some infections only infect people with another infection
list severe influenza predisposing co morbidities
asthma, respiratory viruses, obesity, immunosuppression, immunodeficiency, elderly, diabetic, pregnant
