Viral Hemorrhagic Fevers

Question 1

what are the common clinical manifestations of viral hemorrhagic fevers? What is life threatening and which is not?

Answer 1

Fever, shock, hemorrhage
Shock can be life threatening
the bleeding is usually not life threatening

Question 2

what are the 4 families of VHFs? What are the 2 common morphological features of these viruses?

Answer 2

Arena, fili, bunya, flaviviruses

all enveloped and all have RNA genomes

Question 3

VHF viruses are a zoonsis. What does this mean for their survival and transmission and geography?

Answer 3

Require their reservoir to survive, transmission is usually through a vector (animal, arthropod). Geographically restricted

Question 4

Describe primary VHF transmission

Answer 4

1)Sporadic cases and outbreaks with humans
2)Accidental transmission to humans and only in areas where human and vector/reservoir habitats overlap
3)Transmissed to humans by vectors or with direct contact with the reservoir, not by human-human contact
4)

Question 5

Describe secondary VHF transmission

Answer 5

Transmission between humans

Very few VHFs are transmitted between humans (ebola)

Question 6

How does primary transmission of ebola occur?

Answer 6

through contact with bats or primates (think bush meat)

Question 7

How does secondary transmission of ebola occur?

Answer 7

direct contact with blood or secretions of infected individuals

Question 8

What is the incubation period of ebola? Are patients infected with the virus infectious when asymptomatic?

Answer 8

Incubation: up to 21 days

Asymptomatic carriers are not infectious

Question 9

What is the mortality rate for people infected with ebola and how do they die?

Answer 9

70% mortality for those infected and death from hypovolemic shock and multi organ failure

Question 10

Describe the 4 modes of pathogenesis of VHFs

Answer 10

1) Uncontrolled cytokine response causing a cytokine storm
2) infection and necrosis of the liver causing decreases in clotting factors contributing to bleeding
3) increased vascular permeability causing fluid loss
4) infection of adrenal glands causing a decrease in steroids leading to hypotension and hypovolemic shock

Question 11

How are specific VHFs diagnosed?

Answer 11

Diagnosis is initially based on clinical criteria and judgement with lab testing done to confirm/exclude diagnosis

Question 12

What are the different methods of laboratory diagnoses of VHFs?

Answer 12

Serology of IgM and IgG

Molecular methods: RT-PCR (all VHFs are RNA viruses)

Question 13

How are viral hemorrhagic fevers treated?

Answer 13

With a few exceptions, there are no cures and no real treatments
Supportive care to manage symptoms (rehydration)