22. Emerging viruses

Question 1

what are the 4 states of host virus interactions?

Answer 1

stable
Evolving
dead end
resistent host

Question 2

what is a stable virus host interaction?

Answer 2

the virus and human can survive
like herpes
herpes can only infect humans so would be bad if it killed them

Question 3

what is an evolving host virus interaction?

Answer 3

virus moving to an immunologically naive population
- from animals
- from one part of the world to another
eg Ebola or SARS-CoV-2

Question 4

What is a Dead-end virus host interaction?

Answer 4

spread by a vector but once it infects humans the human cannot transmit it on

Question 5

what is a resistant host virus host interation?

Answer 5

the virus cannot infect the host and the infect is blocked

Question 6

What is a reason we are having more emerging viruses?

Answer 6

improving diagnostics leads to more emerging infections but there is just more data not necessarily more viruses

Question 7

what is a newly emerging viral disease?

Answer 7

it is completely new in the global human population

Question 8

what leads to a re emerging viral disease?

Answer 8

a break down of normal control methods causing a virus to become more prevalent in a population

Question 9

what was the point in history where generally disease started spreading rapidly?

Answer 9

when we started domesticating animals and moving into towns
transmission via water, air and direct contact

Question 10

what are the convergent forces for disease emergence?

Answer 10

globalisation and air travel
mega-cities and the poverty in them
Deforestation
altered ecosystems
movement of people and goods
microbial evolution

Question 11

how do we initially recognise new emerging diseases?

Answer 11

occurrence of a outbreak
development of diagnostic techniques like being able to detect viruses in sewage

Question 12

what new viruses are more likely to be recognised?

Answer 12

clinically unique viruses that have distinct symptoms

Question 13

why was zika virus so hard to identify?

Answer 13

very similar symptoms to dengue to malaria

Question 14

what contributes to emergence of new viral diseases?

Answer 14

virological determinants
environmental factors
host determinants
host population determinants
new tech for viral diagnosis

Question 15

what are the virological determinants?

Answer 15

mutation
recombination
reassortment
fitness
adaptation

Question 16

what are environmental factors?

Answer 16

ecological and zoonotic influences

Question 17

what are host determinants?

Answer 17

specific risk behaviours
innate resistence
acquired immunity
physiological factors

Question 18

what are host population determinants?

Answer 18

behaviours
Social
transport
commercial
iatrogenic factors (caused by medical examination or treatment)

Question 19

why do emerging RNA viruses evolve much faster then DNA viruses?

Answer 19

1. RNA viruses use Viral RdRp with very higher error rates
2. RdRp don’t have proof reading ability
3. DNA viruses use host DdRp which are more accurate

Question 20

what do high mutation rates in RNA viruses result in?

Answer 20

Quasispecies

Question 21

what are Quasispecies?

Answer 21

all the viruses in one body will have slightly different genomes that make up the consensus genome for the virus
- minor population variants

Question 22

what causes emergence of new viral phenotypes?

Answer 22

mutation and recombination
closely related segmented viruses reassort their genome in dual infections
both DNA and RNA viruses can undergo recombination with other closely related species like coronaviruses

Question 23

what is a controversial method of creating emerging viruses?

Answer 23

genetic engineering in gain of function research with bird flu and ferrets
dangerous and was not done in proper containment
altering things to find out what makes a human infectious virus and made a human infecting virus

Question 24

where do many emerging viruses come from?

Answer 24

zoonotic viruses
Especially bats

Question 25

West African ebola outbreak 2014 determinants

Answer 25

viral: evolution of the viral genome possibly making enhanced transmission environmental: zoonotic transmission so contact with wildlife host: burial customs like touching the dead host population: transport and outbreak along a trading route

Question 26

what changed between the normal Ebola outbreaks and the 2014 Ebola outbreak?

Answer 26

most outbreaks were in isolated villages that could be easily contained but the 2014 outbreak happened in a village along a new major transport route. the main change was the location

Question 27

how are the current Ebola outbreaks contained?

Answer 27

mainly by quarantine and rapid testing high success vaccine so introduced ring fence vaccination

Question 28

what is the disadvantage of the Ebola vaccine?

Answer 28

it is only effective against 1 strain

Question 29

Zoonotic transmission of Coronaviruses

Answer 29

they have intermediate reservoirs from bats - MERS = camels - SARS = civet cats - SARS-CoV-2 = some wild animal mostly respiratory but also infect other tissues Airborne transmission in small and large droplets

Question 30

what are most human coronavirus?

Answer 30

common colds

Question 31

what is the biggest difference in epidemiology between SARS-CoV and SARS-CoV-2?

Answer 31

SARS-CoV is believed not to be spread until you have symptoms SARS-CoV-2 can be transmitted asymptomatically so people can spread it without knowing

Question 32

what is the interspecies transmission of SARS-CoV?

Answer 32

bats transmits to palm civet and some small evolution before passing on to humans transmission can occur both ways between humans and civet cats as the viruses are very similar

Question 33

why are bats big reservoirs for viruses?

Answer 33

they can persist without much harm to the bats bats live in big flocks so lots to infect

Question 34

who does MERS-CoV mostly infect and where do they acquire that infection?

Answer 34

People with co morbidities and contact with camels for sport/eating/transport

Question 35

what is the difference between SARS-Cov and SARS-CoV-2?

Answer 35

the furin cleavage site on the spike protein

Question 36

how is the SARS-CoV-2 spike protein different?

Answer 36

part of the protein is cleaved by the host cell proteins before it leaves the cell make it more pathogenic and transmissible

Question 37

what was transmission pathway for SARS-CoV-2?

Answer 37

food markets to local humans spread around the local city international travel made it spread around the world

Question 38

how has the disease SARS-CoV-2 changed over time?

Answer 38

newer variants are more transmissible but less virulent latest varients don't enter the lower respiratory tract

Question 39

what changing ecological factors have been linked with emerging diseases?

Answer 39

installing dams or irrigation rerouting wildlife migration patterns wildlife smuggling air conditioning deforestation Urbanisation

Question 40

what increases human contact with arthropod/insect vectors?

Answer 40

movement to native habitats due to expanding population increasing vector density and spread - changing climate

Question 41

how does Zika virus mostly exist?

Answer 41

in a stable life cycle in an arthropod vector and an animal

Question 42

what happens when Zika virus jumps to humans?

Answer 42

evolve and create a new life cycle without the arthropods reservoir

Question 43

what are the symptoms of Zika?

Answer 43

most people have no overt symptoms in pregnant people it causes foetal abnormalities

Question 44

what happens West Nile virus enter humans?

Answer 44

it is a dead end virus so can't be transmitted on

Question 45

how do Zika virus outbreaks occur?

Answer 45

Naive population is badly effected but develop immunity to protect against reinfection the outbreaks occur in waves as immunity wanes and the virus can take over again

Question 46

what are the 2 phases of prevention and control of emerging disease?

Answer 46

investigative phase Interventional phase

Question 47

what happens in the investigation phase of disease control?

Answer 47

1. disease is characterised 2. assess the risk to the population 3. infectious agent must be identified and characterised 4. Development of diagnostics 5. develop integrated approach

Question 48

what happens in the interventional phase of disease control?

Answer 48

1. commnication with population 2. Technology transfor to local agencies 3. public health measures like vector and water management 4. recognition of the effect of human activity on disease pattern 5. global surbeillance and warning systems