Lecture 6- Viruses

Question 1

Name the forms of Direct transmission

Answer 1

Direct:
-Person to person contact (=Ebola)
-Droplet transmission (sneeze=covid)

Question 2

Name the forms of indirect transmission:

Answer 2

Indirect:
-Airborne transmission (dust particles with droplet nuclei=chickenpox)),
-Vector transmission (picked up by carrier; mosquito= malaria)
-Waterborne (infecting water supply=cholera)

Question 3

What is virulence/ virulent bacteria

Answer 3

It is how much the virus/ bacteria affects the hosts fitness
-highly virulent creates more offspring
-if too virulent, it can kill host before being transmitting

Question 4

how does natural selection favor viruses:

Answer 4

-how severe the disease they cause is
-how easy it is for hosts to catch it (transmissibility)

Question 5

give an example of a more virulent and less virulent virus

Answer 5

more: cholera; can easily infiltrate water systems

less: sexually transmitted diseases; host needs to be active to transmit virus

Question 6

What is an outbreak, epidemic, pandemic and endemic:

Answer 6

Outbreak: sudden increase in cases above what is usually expected (town)

Epidemic: outbreak goes beyond small/ restricted areas. (province)

Pandemic: epidemic that has spread through a large region, multiple continents/worldwide.(country)

Endemic: When a disease is consistently present in a particular region, making it predictable.

Question 7

What makes viruses so adaptable (3)

Answer 7

-simple construction (viral genome)
-short generation time (easily picked up and transmitted)
-high mutation rates (frequent errors means more mutations)

Question 8

Viruses evolve in two ways, what it antigenic drift?

Answer 8

-In host, viruses undergo slow/limited evolution

basically there are small changes in the virus that occur gradually though the accumulation of mutations
=new strains of virus

Question 9

Viruses evolve in two ways, what is antigenic shift?

Answer 9

Viruses show rapid evolution when they infect new hosts

basically large, abrupt changes that occur often because the cell has been infected by multiple viruses = little no to protection against

Question 10

What are the two influenza subtypes?

Answer 10

-Hemagglutinin: binding+ selectivity

-Neuraminidase: let new copies of virus out of cell to infect others

Question 11

Why is influenza “swine flu” an example of antigenic shift?

Answer 11

-It was a virus that produced large and rapid changes.

-people were affected because immune systems did not recognize it (no natural immunity)

Question 12

Why was the 2009 swine flu virus highly transmissible, but not highly virulent, in comparison to the 1918 flu?

Answer 12

2009; It was easily passed from host to host, but most people recovered, few people died.

1918; the second wave killed young people as it triggered immense immune response that destroyed hosts cells meaning it was highly transmissible and virulent, but …quickly became less virulent over time (antigenic drift)

Question 13

How did the 1918 flu evolve into the 2009 flu and then into seasonal flu

Answer 13

-in 1918 it was a bird flu that moved into humans
-we gave that to pigs
-pigs turned it into swine flu

-in 2009, it swapped genes with another bird, becoming H1N1 pandemic

Question 14

Why is commensalism related to bats and viruses

Answer 14

Commensalism is when one individual receives benefit, and the other is indifferent; bats are a reservoir for viruses (ebola), as bats developed some immunity, the virus co exists without killing them.

Question 15

What are early and late symptoms of ebola

Answer 15

Early: arthritis, backache, chills, fatigue, nausea

Later: Gastrointestinal bleeding, eye and genital swelling, hemorrhagic rash (cytokines=permeability of blood vessels)

Question 16

Why is 1918 flu so successful compared to ebola 2014

Answer 16

-Although both were very swift and lethal ,
Ebola transmission is more difficult than influenza because it requires close personal contact with body fluids (can be avoidable by quarantine, protective equipment…)

Question 17

Even if ebola was not easily contagious, how did it manage to kill so many people in Africa?

Answer 17

-because transmission can be shaped by environment and infrastructure, the epidemic was bigger than previous outbreaks because it happened in more densely populated areas

Question 18

How is coronavirus mainly transmitted, how was this analyzed on train passengers in china

Answer 18

-through respiratory droplets;

time and location are important, as the closer you are for a longer time=the more likely you are to receive the virus

Question 19

Whats the difference between a RT-PCR test and an Rapid antigen test

Answer 19

RT; amplifies the amounts of RNA and DNA

Rapid: no amplification, it needs the signal to be large enough to detect

Question 20

Why is covid 19 considered a pandemic

Answer 20

-more cases than expected on multiple continents
-spread rate very unpredictable