• Their infections show very wide clinical spectrum: vary from subclinical or mild to severe or fatal disease.

• Severity of infections depends on:

  • Host factors & immunologic status

  • Virulence of viral strain

  • Innoculum dose that infects human

• Show a distinct geographical distribution, esp. in tropical parts of the world.

• Occur from spring to late fall when climatic conditions (warm climate&rain) favour mosquito proliferation.
  

PATHOGENESIS

Replicate in the gut of vector → during blood sucking, transmit to human via saliva → entering from skin → 1st replication in epithelial cells → blood and lymph circulation → target organ (vascular endothelium and reticuloendothelial cells) → 2nd replication → viremia → invade multi-organs (brain, liver, kidneys, muscles)

Category: Microbiology Notes