Microbiology 5: Patterns of viral infection Flashcards
Define the term Tropism
The tropism of a virus is the place where it replicates
What defines the tropism of a virus
Tropisim may be determined by the expression of the host cell receptor. HIV enters cells through the CD4 molecule found on T cells.
Compare, with named examples, the different modes of transmission of viruses
add pic Viruses in skin can be transmitted by direct skin contact- poxvirus Viraemic viruses are transmitted through blood- ebola and dengue virus Enteric viruses are transmitted through the fecal oral route- poliovirus, norovirus, hepatitis A virus Viruses may be shed into the oral cavity and transmitted in saliva ( human cytomegalovirus, EBV, mumps) add pic
Define nosocomial
Acquired in hospital
Define iatrogenic
relating to illness caused by medical examination or treatment.
List the differnt outcomes of infection by viruses?
Acute Infection Persistent Infection Latent re-activating Infection Slow Infection Oncogenesis
What is an Acute Infection?
An infection that is followed by viral clearence Influenza
What is an persistent infection?
Persistant infections are infections that are not cleared by the adaptive immune response. They may be chronic or lifelong(latent, slow) Chronic - low level replication in tissues which regenerate (EXAMPLE: Chronic carriers of hepatitis B and C viruses.) Latent - viral genomes are maintained but no virus is seen until episodes of reactivation at times at which you are immunocompromised. EXAMPLE: herpes viruses
Describe and give an example of an latent virus infection?
Herpes simplex virus The virus establishes a latent infection in terminally differentiated and non-dividing nuerons of the peripheral nervous system.
What is oncogenesis?
A number of viruses are suspected of causing cancer in animals, including humans, and are frequently referred to as oncogenic viruses. Examples include human papillomaviruses, the Epstein-Barr virus, and the hepatitis B virus, all of which have genomes made up of DNA. Oncogenesis - affect the way our cells control themselves
What type of cancer does Hepatitus B and C cause?
Hepatitis B and C viruses cause hepatocellular carcinoma
Name some cancers that can be caused by the Epstien-Barr Virus
Burkitt’s Lymphoma Hodgkin’s Lymphoma Nasopharyngeal Carcinoma
How does Varicella Zoster virus cause shingles and what disease does it also cause?
Virus enters the body through the respiratory route VZV can infect many cell types including peripheral blood mononuclear cells (PMBCs) and skin cells From the skin site it can infect sensory neurones where it remains latent Virus can be reactivated when cellular immunity is impaired causing a painful rash at nerve endings - SHINGLES You only get symptoms after secondary viraemia Incubation Period: 14 days
How is poliovirus transmitted.
Poliovirus transmitted by fecal oral route
Where does Rubella have a strong tropism for?
Rubella causes mild rash except in early stage fetus where virus has a strong tropism for dividing neuronal tissue.
