Routes of infections
✓ skin
✓ alimentary tract
✓ respiratory tract
✓ genital tract
✓ in utero
Stages of viral infection
- Initiation of infection at primary site
- Replication of virus and spread to secondary site
- Manifestations of the viral diseases
Manifestations of the viral diseases; dependent on the virulence of the virus and host factors
✓ age, general health and immune status of the host
✓ dose of infective virus
✓ genetics of host and the virus
Severity of viral infections
✓ inapparent infection
✓ acute infection
✓ chronic or persistent infection
(incubation period) stages in the spread of a typical systemic viral infection
✓ infection of susceptible host w/ viral pathogen
✓ replication at site of tissue invasion
✓ spread to and replication in regional lymph nodes
✓ entry into bloodstream
✓ primary viraemia
✓ replication in bone marrow, and other organs
✓ secondary viraemia
✓ lesions in target organs
✓ clinical signs of the disease
types of host cells in terms of virus-host interaction;
- permissive cell
- non-permissive cell
- semi-permissive cell
cellular changes resulting from replication of virus
- cell death
- cell lysis
- transformation of cells
- alterations in cell’s morphology
- steady state of infection w/o causing injury to the host cell
- cytopathic effects
types of virus infection at cellular level
- abortive infection
- lytic infection
- persistent viral infection
are the intracytoplasmic eosinophilic inclusion bodies in the neural cells and are pathognomonic of rabies
negri bodies
are small, multiple inclusions found in vaccinia-infected cells
guarnieri bodies
are large inclusions seen in fowl pox
bollinger bodies
are very large inclusion bodies seen in the molluscum contagiosum infected cell
molluscum bodies
routes by which viruses are shed
✓ coughing and sneezing (aerosol)
✓ faeces
✓ body fluids (semen, saliva, urine, milk)
✓ arthropod vectors of arboviruses
✓ surgical procedures for some blood-borne viruses
✓ transplacental route/ via birth canal
✓ DNA of germ cells
