Smallpox/Rabies Flashcards
Structure of Pox viruses
ds DNA
Contain RNA polymerase (not infectious genome)
no symmetry
unenveloped
One thing that distinguishes Pox viruses from other DNA viruses
they contain a DNA-dep RNA pol: only DNA virus that does this. reason: they repl in the cytoplasm.
Pox viruses form what in the cytoplasm?
INclusion bodies
Which viruses form inclusion bodies in teh cytoplasm? which form inclusion bodies in the nucleus?
Cytoplasm: pox viruses.
Nucleus: herpes
How is smallpx transmitted?
Resp
How does smallpox manifest in the body?
First viremia: lungs, liver, spleen.
Second viremia: skin. x 10 days later
Clinical presentation of smallpox/
papules, vesicles, pustules.
What is an example of pantropic virus?
Measles, smallpox.
What is the tropism of Hepatitis?
Liver
What type of vaccine for smallpox?
Live, vaccinia virus (similar to but not identical to smallpox)
Has smallpox been eradicated?
YES
What is the strategy for dealing with isolated cases of smallpox that arise? Why did it work?
Ring vaccination. Worked because post-exposure vaccination works up to 4d post-exposure.
Smallpox has how many serotypes?
ONE.
Does smallpox have non-human reservoirs?
NO
Does smallpox result in any asymptomatic infections?
NO.
What is an example of a pox virus that we might see clinically?
Molluscum contagiosum
How is molluscum contagiosum transmitted?
Cutanous contact
How long is the incubation for mollusc. contag?
2-8 wks
What is the clinical presentation of mollusc. contag?
after 2-8 weeks, pearly white papules appear.
What type of virus is rabies?
Rhabdovirus.
Characteristics of rhabdoviruses?
Bullet-shaped, enveloped, helical, -RNA (single molecule)
Does the rabies/rhabdovirus bring along its own polymerase?
YES, brings in its own RNA-dep RNA pol.
How is rabies transmitted?
Through the bite of an infected animal that has virus in its saliva.
Tropism of rabies?
Nerve cells.
Describe the replication of rabies virus in an infected animal.
wave of viral replication moves up peripheral nerves from the bite, infects CNS, and then down a neural route to the salivary glands. Virus can grow in sal glands of rabid animals, this providing virus in the bite that is transmissive.
How long is the rabies incubation period?
Long: week to months.
Rabies: fatal to what organisms?
Usually fatal for human, dog
Initial and later sx of rabies?
Initial: fever, anorexia
Later: hydrophobia due to pain with swallowing.
How does herpes simplex infect the CNS?
Via neural pathway (same as rabies)
How do most viruses infect the CNS?
via viremia. Ex: HSV, VZV are latent in sensory ganglia. when reactivated, move down sensory nerves to the cutaneous site at which lesions appear.
Diagnosis or Rabies depends on what unique finding?
Negri bodies (cytoplasmic inclusions). Fluorescent Ab to rabies confirms that these bodies are from rabies virus.
Review of inclusion bodies: Rabies have what? Pox viruses have what? Herpes have what:
Rabies: cytoplasmic Negri bodies
Pox: cytoplasmic inclusions
Herpes: nuclear inclusions
What type of vaccine is used for rabies?
Killed. Cultured in diploid cells, then killed/inactivated.
With rabies, can you immunize after infection?
Yes: the long incubation allows for this. however, once Sx are seen in the CNS, death will ensue. Generally the vaccine is given in 5 doses.
What is special about rabies treatment after possible contact with the virus?
Combination of passive immunization (pooled donated human serum, which is given to delay symptoms) and killed vaccine is given.
