8.1 Haemorrhagic Fever

Question 1

Which four virus families are involved with causing hemorrhagic fever?

Answer 1

• Arenaviridae (Group 5)
• Filoviridae (Group 5)
• Flaviviridae (Group 4)
• Bunyaviridae (Group 5)

Question 2

List the viruses in each family causing hemorrhagic fever

Answer 2

• Arenaviridae ,, Lassa Fever + Argentina, Bolivian, Venezuelan and Brazilian Hemorrhagic fever
• Filoviridae ,, Ebola and Marburg Hemorrhagic fever
• Flaviviridae ,, Yellow Fever and Dengue Hemorrhagic fever
• Bunyaviridae ,, Rift valley, Hemorrhagic fever with renal syndrome ad Crimean-Congo hemorrhagic fever

Question 3

List the types of clinical features caused by dengue

Answer 3

• Most are asymptomatic
• Classical dengue fever ,, fever, rash, headache, muscle/join pain, nausea, vomiting and rarely hemorrhagic — recovery period of several weeks
• Dengue hemorrhagic fever(DHF)/Dengue shock syndrome(DSS) ,, fever, hemorrhagic, vascular leakage, petechiae, hepatitis

Question 4

What is ‘antibody dependant enhancement’?

Answer 4

Antibody dependant enhancement occurs when the antibodies generated during an immune response recognise and bind to a pathogen but are unable to prevent infection instead these antibodies act as a ‘Trojan horse’ and allow for the pathogen to get into the cells and exacerbate the immune response.

Eg. The first infection with a serotype of DEN produces neutral antibodies to that serotype, the second infection with a different serotype will not be neutralised by the first set of antibodies and instead allow macrophages to take up the virus and spread the virus through the body

Question 5

Give reasons for the increase in the spread of dengue

Answer 5

• unplanned urbanisation
• lack of mosquito control in these newly populated centres
• advent of modern air travel ,, this increased the movement of people who were infected and carrying DENV
• increased international commerce and trade has led to vector transport
• spread of vector due to changing environment

Question 6

What is the major issue with dengue vaccines?

Answer 6

The problems in the development of a vaccine for dengue reflect the requirements for the vaccine to provide immunity to each of the four serotypes (be tetravalent)

This is because ,,
- infection with one serotype provides long-term immunity to this serotype but not to others
- sever DEN infection is associated with prior infection with a different serotype
- one or several serotypes can circulate simultaneously and can change from one season to the next

Question 7

How is the ChemeriVax-DEN vaccine made?

Answer 7

The genes that encode for the YFV prM-Env have been replaced by those of DENV ,,

The Env protein being the dominant viral antigen which neutralises the antibodies and the prM, an enveloped protein of unknown function also inducing the neutralising of antibodies

Question 8

What were the contributing factors causing the mortality rate in the 2000 Gulran outbreak?

Answer 8

• lack of awareness of healthcare workers of hemorrhagic fever
• taliban government: underdeveloped health system
• no reporting of suspected cases following the first cases
• the DoH only initiated investigation two weeks later
• control measures and treatment were 25 days late
• general public lack of awareness

Question 9

How was dengue and yellow fever excluded as possible causes of the 2000 Gulran outbreak?

Answer 9

• is not carried by mosquitos
• does not share similar clinical features

Question 10

Why is CCHF the most likely cause of the 2000 Gulran outbreak?

Answer 10

Was found in the same area with the same clinical features and was isolated from patients samples during the second outbreak.