Zoonoses and emerging human viral infections

Question 1

Definition of an emerging disease

Answer 1

A new disease of humans, not previously seen or a recurrence of an infection that has previously disappeared from the human population

Question 2

Definition of enzootic

Answer 2

infection maintained in an animal population

Question 3

Definition of epizootic

Answer 3

increased transmission of infection in an animal population

Question 4

Why are viruses host specific?

Answer 4

• few genes

- entirely dependent on host cell for replicaton

Question 5

Adaptive mechanisms of zoonotic viruses

Answer 5

• point mutation
• recombination
• reassortment
• host RNA modification

Question 6

Define a quasi-species

Answer 6

A population of related viruses that differ by point mutations

Question 7

Possible effects of point mutations

Answer 7

Altered protein structure

• altered antigenicity
• altered drug senstivity
• altered function

Non-coding region
- altered level of expression

Question 8

Describe the Poliovirus and tissue tropism

Answer 8

• Enterovirus that replicates in GALT
• change in tissue tropism triggered by favourable mutation
• replicate in CNS

Question 9

Examples of viruses that often use recombination

Answer 9

• coronaviruses
• picornaviruses
• retroviruses

Question 10

Examples of viruses that often use reassortment

Answer 10

• Influenza A
• rotaviruses
• bunyaviridae

Question 11

Another name for virus reassortment

Answer 11

Antigenic shift

Question 12

Characteristics of fulminant clinical illness

Answer 12

• fever and rash
• encephalitis
• viral haemorrhagic fever
• shock syndrome

Question 13

Pathogenesis of Rabies

Answer 13

Enters nerve endings by binding acetyl choline receptors

Travels up axons to the brain

Question 14

Reservoir hosts of Rabies

Answer 14

• carnivora

- chiroptera (bats)

Question 15

Describe Marburg and Ebolavirus disease

Answer 15

• Haemorrhagic fever

Question 16

Contributing factors for Ebola outbreaks

Answer 16

• poverty
• destroyed infrastructure
• no trust in authority
• delayed recognition of outbreak
• collapsed healthcare system
• slow international response

Question 17

Incubation period of Ebola

Answer 17

2-21 day

Question 18

Treatment of Ebola

Answer 18

• replace lost fluid

- maintain BP

Question 19

What is a spill over host?

Answer 19

A second animal host that is not the usual reservoir

Question 20

Problems with spill over hosts

Answer 20

• amplify infection
• often get ill
• contact with humans

Question 21

Types of arthropod vectors

Answer 21

• mosquitoes
• ticks
• sandflies

Question 22

Most common VHF in SA

Answer 22

Crimean Congo Haemorrhagic fever

Question 23

Vector of Congo fever

Answer 23

tick

Question 24

Yellow fever virus type

Answer 24

Flavivirus

Question 25

Animal reservoir of YF

Answer 25

forest monkey

Question 26

Vector of YF

Answer 26

various species of Aedes and Haemogogus mosquitoes

Question 27

Vector of Dengue fever

Answer 27

Aedes Aegypti mosquito

Question 28

Predominant cycle of dengue fever

Answer 28

Urban

Question 29

Steps to becoming a human infection

Answer 29

- exposure to reservoir - cross species infection - transmission to a 2nd human host - adaptation to a new species - sustained human to human transmission

Question 30

Staged of an animal virus

Answer 30

- agent only in animals - primary infection - limited outbreak - long outbreak - exclusive human agent

Question 31

Factors which determine the ability of an organism to establish itself as a human infection

Answer 31

- duration of infectivity - ease of transmission to new hosts - milder disease phenotype - capacity for immune evasion - population size/density

Question 32

Define a reproduction rate

Answer 32

The average number of secondary cases generated by a single infected individual

Question 33

Define herd immunity

Answer 33

Collective immunity to a pathogen in the population

Question 34

Phases of global alert in pandemic monitoring

Answer 34

``` 1 - animal infection 2 - potential pandemic threat 3 - sporadic human cases 4 - significant increase in risk of pandemic 5 - pandemic is imminent 6 - pandemic phase ```

Question 35

Virology of influenza virus

Answer 35

Orthomyxovirus Segmented genome 2 envelope glycoproteins

Question 36

Why is influenza so antigenically variable?

Answer 36

- Immunity is directed to HA | - high mutation rate of this region

Question 37

How does a flu pandemic arise?

Answer 37

- new strains of influenza arise from reassortment between human and avain flu strains

Question 38

Human factors responsible for emerging infections

Answer 38

- population growth - urbanisation - population movement - global air travel - food production

Question 39

Viral factors responsible for emerging infections

Answer 39

- new vector - new vertebrate hosts - antigenic variation - altered pathogenicity - altered tissue tropism

Question 40

Ecological factors responsible for emerging infections

Answer 40

- altered prevalence of animal species - proliferation of vectors - expansion of vectors to new areas