Entry into the Host Gastrointestinal tract-ahostile environment; gastric acid, bile salts, etc Genitourinary tract-relatively less hostile than the above, but less frequently exposed to extraneous viruses Conjunctiva-an exposed site and relatively unprotected
Entry into the Host • Gastrointestinal tract- a hostile environment; gastric acid, bile salts, etc • Genitourinary tract-relatively less hostile than the above, but less frequently exposed to extraneous viruses (?) • Conjunctiva - an exposed site and relatively unprotected
Sites of virus entry Eyes(conjunctiva Mouth Respiratory tract Skim: abrasion arthropod vectors Alimentary canal Urogenital tract
Sites of virus entry
Transmission patterns HorzontalTransmission: Direct person-to person spread Verticaltransmission: Relies on PerSiSTe cE of the agent to transfer infection from parents to offspring. Several forms of vertical transmission can be distinguished: 1 Neonatalinfection at birth, e.g. gonorrhoea AIDS 2. Infection in utero e.g. syphilis, CMV, Rubella CCRSLAIDS 3. Germ line infection -via ovum or sperm
Transmission patterns • Horizontal Transmission: Direct person-toperson spread. • Vertical Transmission:Relies on PERSISTENCE of the agent to transfer infection from parents to offspring. Several forms of vertical transmission can be distinguished: • 1.Neonatal infection at birth, e.g. gonorrhorea, AIDS. • 2.Infection in utero e.g. syphilis, CMV, Rubella (CRS), AIDS. • 3. Germ line infection - via ovum or sperm
Primary Replication Having gained entry to a potential host, the virus must initiate an infection by entering a susceptible cell. This frequently determines whether the infection will remain localized at the site of entry or spread to become a systemic infection
Primary Replication • Having gained entry to a potential host, the virus must initiate an infection by entering a susceptible cell. This frequently determines whether the infection will remain localized at the site of entry or spread to become a systemic infection
Localized infections iruses PrimaryReplication Rhinoviruses URT Rotaviruses Intestinal epithelium Papillomaviruses Epidermis
Localized Infections • Viruses Primary Replication • Rhinoviruses U.R.T. • Rotaviruses Intestinal epithelium • Papillomaviruses Epidermis