Lecture 35

Question 1

1. Where was Ebola first identified?
2. What are the symptoms?
3. When does death occur?
4. What are some other hemorrhagic fevers?

Answer 1

1. From the village of Yambuku, northern Zaire. Blood taken from a Belgian nun who died, thought to be yellow fever, but instead was Ebola. Named after the river near Yambuku.
2. Symptoms:
   
   1. Begin 2 days to 21 days after containing the virus. Fever, sore throat, muscle pain, headache, followed by vomiting, diarrhea, skin rash and by decreased liver and kindney function and bleeding externally and internally.
3. Typically six to sixteen days after symptoms appear, is due to low blood pressure resulting from fluid loss.
4. Lassa fever, Marburg Hemorrhagic Fever, Hantavirus Pulmonary Syndrome.

Question 2

1. What is the causitive agent of the disease?
2. What is the Genus?

Answer 2

1. Family - Filoviridae: filamentous, coiled. 80 nm X up to 14,000 nm.
2. Ebolavirus
   
   1. Zaire ebolavirus - most dangerous
   2. Sudan, Tai Forest, Budibugyo - also cause disease in humans.
   3. Reston virus - does not cause disease in humans, does in other primates.

Question 3

1. What kind of virus is Ebola?
2. Genes:
   
   1. NP?
   2. VP35?
   3. VP40?
   4. GP?
   5. VP30?
   6. VP24?
   7. L?

Answer 3

1. Negative strand RNA virus. Genome is 18 to 19 kb in size. Ebola RNA genome has seven genes.
2. Genes:
   
   1. nucleoprotein: encapsidates the genome, protecting it from nucleases.
   2. polymerase cofactor: blocks immune system respone.
   3. matrix protein: virus assembly and budding.
   4. envelope glycoprotein: binds to target cell receptor/infect taget cells.
   5. minor nucleoprotein: transcription anti-termination factor.
   6. membrane-associated protein: blocks immune system response.
   7. RNA dependent RNA polymerase: transcription of genes, genome replication.

Question 4

Describe the life cycle of ebola

Answer 4

1. Attachment of virus to cell surface receptors.
2. Fusion of viral membrane with cell membrane.
3. Entry of virus into cell.
4. Release of nucleocapsid.
5. Transcription of genes into plus-strand mRNAs.
6. Production of viral proteins
7. Replication of genome.
8. Assembly of virus progeny
9. Budding off of virus, acquirig envelope from host cell membrane.
10. New viruses infect other cells.

Question 5

1. What kind of cells does Ebola replicate in?
2. How does infection begin?
3. What does the virus target when in the body?
4. What does immune system cells do?

Answer 5

1. In many kinds of cells. Myeloid cells, lymphocytes, liver cells, endothelial cells, etc.
2. Begins by contact of the virus with mucous membranes or entry through skin breaks.
3. Targets endothelial cells (line the inside of blood vessels), liver cells, and several kinds of immune system cells.
4. Carry the virus to the lymph nodes, where the virus continues to reproduce. From lymph nodes, the virus enters the lymphatic system and bloodstream and spreads throughout the body.
   
   1. Destruction of immune system cells leads to a weakened immune response to the virus.
   2. Destruction of endothelial cells, seen as widespread hemorrhaging, results in edema (swelling) and hypovolemic (low blood volume) shock.

Question 6

1. What is thought to serve as the reservoir?
2. How is it spread to humans?
3. Why is human expansion negative in this particular case?

Answer 6

1. Recent evidence implicates bats, especially fruit bats. The virus is present also in monkeys and other wild animals of Central Africa. EVD is zoonosis.
2. From the wild - handling of fruit bats, monkeys, other “bushmeat”. Contacting blood and tissue of an infected animal. Possibly from fruit fed on and dropped by fruit bats. From another person - contact with body