Influenza Pandemics and Epidemics

Question 1

How many genes does an influenza virus have

Answer 1

8 genes

Question 2

how does an influenza virus change its surface antigens

Answer 2

• antigenic shift - an abrupt change that results in the release of a new virulent form of the virus every few decades
• antigenic drigt - gradual change in the surface antigens that is sufficient to allow the virus to evade recognition by the immune system but it cannot maintain its high virulence

Question 3

How many people die from seasonal flu a year

Answer 3

About 10,000 people in the UK (2 per 1000 infected), and half a million worldwide, die from influenza each year

Question 4

in non pandemic years what are deaths like versus pandemic years

Answer 4

• In non-pandemic years there is high death rate in elderly and other vulnerable people but with pandemics the deaths are in younger adults and due to a virulent pneumonia with massive destruction of the lung tissue

Question 5

what is the natural reservoir of the influenza virus

Answer 5

• Wild ducks and other aquatic birds = these can infect other domestic birds and chickens which can then infect humans

Question 6

define epidemic

Answer 6

the occurence of more cases of disease, injury or other health conditions than expected in a given area or among a specific group of persons during a paritciular peroid

Question 7

define pandemic

Answer 7

• this is when an epidemic spreads across mutiple contients and regions

Question 8

What are the types of epidemics

Answer 8

• Common source epidemics
• propagated epidemics
• mixed outbreak

Question 9

What is a common source epidemic

Answer 9

• a group of people get infected from a common source of infection
• these infected people cannot transfer the infection to other people

Question 10

What is a propagated epidemic

Answer 10

• in a propagated epidmeic a group of people get infected from a common source of infection
• these infected people can then transfer the infection to other people

Question 11

What is a propagated epidemic

Answer 11

• in a propagated epidmeic a group of people get infected from a common source of infection
• these infected people can then transfer the infection to other people
• therefore the number of people infected group expotentially

Question 12

What is a mixed outbreak

Answer 12

• has features of both common source epidemics and propagated epidemics

Question 13

How do epidemics spread from one person to another

Answer 13

• Airbourne infection
• arthropod transmission
• contact transmission
• faecal oral transmission

Question 14

Name the two types of droplet infections and what is the difference between them

Answer 14

• Droplets - greater than 5 micrometers

- Droplet nuclei - less than 5 micrometers

Question 15

Name the two types of droplet infections and what is the difference between them

Answer 15

• Droplets - greater than 5 micrometers (transmitted over 1 m)
• Droplet nuclei - less than 5 micrometers (transmitted more than 1m as can remain suspeneded in air as they are smaller)

Question 16

What are the 5 stages of Epidemics

Answer 16

Stage 1
- animal infections only

Stage 2
- human to human transmission

Stage 3
- wide human transmission - expotentional increase

Stage 4
- padnemic activity is decreasing

Stage 5
- disease activity level reaches the level of seasonal flu