L22 - Smallpox Flashcards
how is smallpox spread
secretions from nose and mouth
= respiratory disease
how long after exposure do people develop symptoms
2 weeks
is smallpox related to chickenpox
No
= early rash is often confused with chickenpox
pathogen of smallpox
dsDNA virus = Variola
what is special about smallpox/variola
first disease to be controlled by vaccination
= completely removed from environment
progression of symtpoms for smallpox
Fever - 2 weeks after exposure
2-4 days after fever rash begins to develop
= rash devlops into smallpox
symtpoms - smallpox vs chicken pox
smallpox victims have pox on soles of feet and palms of hand
= very rare in chicken pox
pox is more in extremities and arms/legs than chicken
fever is BEFORE the rash in smallpox
name of family of viruses smallpox comes from
Poxviridae
= includes Vaccinia = the vaccine virus
also includes poxes for a range of animals:
- monkeypox
- camel pox
- cowpox
describe variolas structure
dsDNA virus
brick shaped with multiple lipid envelopes and a core
core holds linear DNA
lateral bodies outside of core
- hold viral proteins for infection
= virus structure is complex and poorly understood
replication cycle of smallpox
- Virus binds and invades into cytoplasm host
- uncoats outermembrane and inner core membrane surrounding genome
- production of early genes via pre-synthesied RNA polymerase
= DNA polymerase/replicative elements
- virus replicates at ‘Viral factories’ in cytoplasm
- once replicated late genes are expressed and new viral molecules formed
what is unique as a DNA virus about smallpox
rreplicates entirely in cytoplasm
= viral factories
describe the variolas genome
linear dsDNA genome
ends of nucletides contain inverted terminal repeat sequences
= tandem repeats and palindromic sequnces
Hairpin loops at very end of DNA formed by palindromic sequnces folding back on themselves
= covalent bonds
= protect from nucleases
what does variola carry with it for ‘early’ gene expression and what is amde in early gene expression for ‘late’ proteins
pre-synthesised RNA polmerase
= genome also holds genes for DNA polymerases
= substitute for host cells
what is variolation - before vaccination
deliberatley infecting sombody with parts of infected people
brief history of smallpox vaccination
Chinese and Indian cultures used variolation for a long time
Lady montague introduced variolation to UK in 1720s
Edward jenner began infecting ppl with cowpox
= found that they didnt get smallpox
