Viral Haemorrhagic fevers

Question 1

Common features of VHFs (viral haemorrhagic fevers)

Answer 1

• enveloped RNA viruses
• animal or insect host
• sporadic human outbreaks
• no effective vaccines or antivirals (apart from yellow fever)

Question 2

Baltimore classification of viruses

Answer 2

Class 4 = +ssRNA

Class 5 = -ssRNA

Question 3

4 virus families contain members causing VHF

Answer 3

• Arenaviridae
• Bunyaviridae
• Flaviviridae (Yellow fever etc)
• Filoviridae (Ebloa etc)

Question 4

Ebola (Filoviridae)

Answer 4

-filo=thread like
-filamentous, pleomorpic particles
5 subtypes
eg Zaire (highest mortality)

Question 5

Filovirus structure

Answer 5

• outer envelope has glycoproteins (GP) on surface
• envelope surrounds a matrix containing the nucleocapsid (NP)
• Genomic RNA is encapsidated by (NP)
• regulatory regions flank the coding regions (7 genes)

Question 6

Filovirus replication cycle

Answer 6

1. filovirus attachment
2. Macropinocytosis
3. early endosome
4. fusion at endosomal membrane
5. release of viral ribonuclear capsid into the cytoplasm
6. viral transcription/translation/reokication
7. budding from host cell membrane

Question 7

Filovirus replication cycle

Answer 7

• Receptor binding
• Genome transcribed & replicated in cytoplasm
• Viral proteins translated
• Proteins & -ve strand genome packaged into particles
• Virus buds from the cell

Question 8

Ebola course of infection

Answer 8

• acute onset (2-21days)
• fever, chills &myalgia
• multisystem involvement (v and d, chest pain, confusion, headache, coma)
• haemorrhage
• shock and convulsions

Question 9

Origin of Ebola

Answer 9

• fruit bats natural host reservoir

- contact

Question 10

Ebola vaccine preparation

Answer 10

-modified human adenovirus

ebola virus glycoprotein gene

Question 11

FLAVIVIRUSES that cause HF: Yellow fever

Answer 11

• liver disease
• acute infection (3-6days incubation)
• death in 20-50% of severe cases
• after 7-10 days illness

Question 12

FLAVIVIRUSES: Dengue

Answer 12

• dengue haemorrhagic fever

- fatality rates 1-10%

Question 13

Arboviruses

Answer 13

• yellow fever

- degue fever

Question 14

Zoonoses and HF

Answer 14

• a disease which can be transmitted to humans from animals

- Arboviruses (arthropod borne)

Question 15

Flavivirus genome organisation:

Answer 15

positive sense RNA genome

-10kb in length

Question 16

YELLOW FEVER

Answer 16

• carlos finlay 1880 and walter reed 1900 established link between mosquitos and yellow fever
• building of panama canal

Question 17

Yellow fever vaccine:

Answer 17

17D

-Live attenuated yellow fever vaccine (mutations in E)

Question 18

Dengue haemorrhagic fever (DHF) - vector control

Answer 18

• aeded aegypti - mosquito host for degue and yellow fever

- yellow fever does not occur in asia

Question 19

Ecological changes influencing VHFs

Answer 19

-travel -globalisation
-air conditioning
-blood transfusion
etc

Question 20

Flavi

Answer 20

yellow fever and degue

Question 21

Filo

Answer 21

ebola