022 How viruses cause disease Flashcards
How is yellow fever transmitted?
By arthropod
What is localised infection?
When the site of entry, infection and disease all occur at the same site.
Why might rhinitis caused localised infection?
Because optimum temperature for replication is 33 degrees.
Describe the infection of papillomavirus?
When there is an abrasion, papillomavirus will enter the site. As the basal keriatinocyte replicates, the virus will replicate along with it. In non-dividing cells, viral DNA amplification occurs. In dividing cells, virus will produce more virions. To begin with, only early genes are expressed and very low levels of protein are made. Later as it replicates to squamous layer, early and late viral genes are expressed and virions are produced.
How long is the minimum time for papillomavirus infections to complete its cycle?
4-6 weeks
Do enveloped or unenveloped virus survive better in environments?
Unenveloped viruses survive better because the envelope is more sensitive to external conditions.
How are most systemic viruses spread in the body?
Through lymph nodes
What is primary and secondary viraemia?
Primary viraemia occure when the virus enters the capillaries through tissues such as lymph nodes. After it is transported to the liver/spleen etc The virus will replicate and exit efferent arterioles as secondary viraemia. The virus can not be transported through its exit portal and release e.g. through respiratory secretions.
What is true and incomplete latency?
True latency is when non-productive and productive phases occur alternatively. E.g. VZV. Incomplete latency is when some cells are productive but others are non-productive e.g. HIV.
What is productive and non-productive infections?
Productive - virus replication with production of virions
How may EBV cause cancers? What is the disease symptoms of EBV caused by?
It infects oral epithelial cells and infects B cells, causing uncontrollable B cell proliferation that could lead to cancer. Heterophile antibodies are produced. T cell activation (CD8) also occurs to control the B cell infection. This, however, contributes to symptoms.
How does Rubella disease depend on host status?
In mothers, it may present as a rash. In fetus it could present as congenital infection
How does herpes simplex disease depend on host status?
In immunocompetent it can present as an ulcer. In immunocompromised, it can present as pneumonia.
