Lecture 7- Evolution and emergence of new viruses

Question 1

Why is viral evolution very fast?

Answer 1

• replicate fast
• large progeny numbers
• Hugh mutation rates

Question 2

What is a quasispecies?

Answer 2

the viral genomes within a single infected patient which are slightly different ti the genome in other patients because of evolution specific to that host

Question 3

What happens when a virus encounters a bottleneck is encountered?

Answer 3

Only one or two quasi species survive

Question 4

what is the purpose of combination therapy in HIV infected patients?

Answer 4

• monotherapy increases the risk of a single nucleotide change creating resistant strains
• In combo therapy virus needs 5/ more simultaneous mutations mutations= unlikely

Question 5

What is the name of the treatment against HIV?

Answer 5

HAART highly active anti-retroviral therapy

Question 6

What is antigenic drift?

Answer 6

Antigens gradually change over a period of time due to pressure exerted by antibodies

Question 7

How do new viruses emerge?

Answer 7

• zoonosis
• genetic variation
• increased exposure- Tavel/ world population
• increased exposure- spread of vector
• new discoveries

Question 8

Name some viruses which were recently discovered

Answer 8

Hepatitis C
HPV 16 and 18
HHV8 - causes kapok’s sarcoma
Merkel cell polyoma virus

Question 9

What influences the emergence of infections?

Answer 9

• Environmental modification
• world population
• climate change
• travel
• farming practice (monoculture)
• immunosuppression
• Medical progress

Question 10

What are arboviruses?

Answer 10

Viruses transmitted to humans by arthropods such as mosquitoes and ticks

Question 11

Name some arboviruses

• what sort of virus do they tend to be?
• what is their host?

Answer 11

Yellow fever
Dengue
West Nile
Chikingunya
- Flaviviruses= single strand positive- sense RNA genomes
- Mosquitoes

Question 12

What causes the levels of arboviruses to increase

Answer 12

• global waring= increased distribution of mosquitoes
• Decrease in mosquito control
• imports
• stagnant water (dams)

Question 13

Which animals are dead end hosts for the west Nile virus?

Answer 13

Horses

Humans

Question 14

What group of viruses does the West Nile virus belong to?

Answer 14

The Japanese encephalitis group of flaviruses- disease goes to the brain

Question 15

Which group of people were most affected by WNV in New York?

Answer 15

The elderly

Question 16

What is Antibody dependent enhancement of Infection? Which viral infection does this apply to?

Answer 16

Dengue Haemorrhagic Fever

• 4 serotypes
• 1st infection you develop antibodies against this serotype
• 2nd infection- antibodies from first serotype make you more sick

Question 17

What are the risk factors for Dengue Haemorrhagic Fever?

Answer 17

• Virus strain
• Pre-eisting anti-dengue antibody (from previous infection, maternal antibodies in infant)
• Age
• Higher risk in secondary infections
• Higher risk in locations with two or more serotypes circulating simultaneously at high levels

Question 18

Why is it that dengue antibodies cause opposite reactions (neutralise or enhance infection)?

Answer 18

NEUTRALISE: homologous antibodies bind tightly to vision and stop it entering the cell
ENHANCE: non-homologous = low affinity binding but doesn’t block. Antibodies can bind to Fc receptors on immune cells and enter easily

Question 19

What are the symptoms of Zika virus?

Answer 19

Headache
Pale skin, rash
Fever
Muscle pain, athralgia
diarrhoea 
red eyes

Question 20

Define the term Zoonosis. What is a potential consequence of Zoonosis

Answer 20

A disease which can be transmitted from animals to humans. Can cause a pandemic but don’t spread easily

Question 21

What was the animal source of ebola

Answer 21

Fruit bats or monkey species

Question 22

How was the spread of Ebola managed?

Answer 22

• Protective ebola suit worn
• Contact tracing and containment
• isolation of infected individuals

Question 23

Where did Severe Acute Respiratory Syndrome originate and spread to? and which animal did it drift from?

Answer 23

• from bats and civets
• started in China
• spread to Vietnam, Singapore

Question 24

How is SARS spread?

Answer 24

Through respiratory droplets

especially through nebulisers in hospitals

Question 25

Which age group doe sit particularly affects

Answer 25

High mortality rate in the elderly

Question 26

Why was the epidemic overcome so quickly?

Answer 26

Long period of time between symptoms and infectious stage so you can isolate the symptomatic individuals

Question 27

Which virus causes SARS? Which receptor does the virus bind to? and with which molecule does it bind?

Answer 27

• Coronavirus (largest RNA virus 30kb and +ve sense RNA)
• envelop spike protein highly plastic can adapt to bind to different receptors
• receptor is ACE-2 protein

Question 28

What is MERS, which virus causes it and which animal species did it originate from?

Answer 28

MIDDLE EASTERN RESPIRATORY SYNDROME

• coronavirus
• fruit bats –> camels –> humans

Question 29

What does MERS cornovirus cause in older infected persons?

Answer 29

• ARDS (acute respiratory distress syndrome)

Question 30

Which receptor does coronavirus bind to?

Answer 30

DPP4 in the lungs

Question 31

Give an example of virus recombination

Answer 31

Swine Flu H1N1- Human flu and Avian flu mix in pigs forming a new virus

Question 32

What is antigenic drift?

Answer 32

where a virus circulates in humans and slowly changes over years.

Question 33

What is H7N9? Where does it originate from?

Answer 33

Bird Flu

China