L19- Epidermiology

Question 1

What is an endemic disease?

Answer 1

Low level frequency of people affected at regular intervals. eg colds and flues

Question 2

What is an epidemic disease?

Answer 2

A sudden increase in frequency above the expected. e.g. chicken pox

Question 3

What is a pandemic disease?

Answer 3

Increase simultaneously over wide area eg. AIDS and swine flu

Question 4

How do we measure the frequency of infection?

Answer 4

1. Morbidity rate- number ill per 100,000

2. Mortality rate- relationship between deaths and cases- shows how severe it is,

Question 5

How do you define an epidemic numerically?

Answer 5

> 400 cases/100,000 population/week

Question 6

What is a common source epidemic?

Answer 6

Sharp rise to a peak and rapid decline. Caused by one source. eg food poisoning from pie shop.

Question 7

What is a propogated epidemis?

Answer 7

Slow rise and gradual decline. Usually with season change e.g. chicken pox.

Question 8

What percentage of the population vaccinated proved herd immunity for these diseases?
a/flu
b.polio
c.measles

Answer 8

a. 90%
b. 70%
c. 90-95% (highly contagious)

Question 9

How can the organism, vaccinated against, change?

Answer 9

Antigenic drift- mutations cause antigens to change so vaccine becomes ineffective

Question 10

Which disease has a 2-3 year cycle of antigenetic drift?

Answer 10

Flu. Orthomyxovirus- ss RNA. New vaccine has to be made frequently.

Question 11

What happens in flues that swaps the RNA around?

Answer 11

Antigenic shift of 2 or more different flu virus strains. There are 8 RNA segments that swap. Can also happen between species e.g. bird flu

Question 12

What are 3 types of control measures for an epidemic?

Answer 12

1. eliminate the source (quarantine)
2. break connection between source and host
3. raise level of her immunity- vaccinate

Question 13

Give 4 examples of emergence of new diseases?

Answer 13

1. HIV/aids virus- 1983 (jumped species barrier)
2. Ebola virus- 1976 (jumped barrier)
3. Legionnaire’s disease- 1976
4. E. coli haemorrhagic colitis- 1982 (jumped barrier)

Question 14

How does legionnaires disease spread?

Answer 14

The bacteria live in amoebae in water and get into cooling systems and aerosols. causes disease in human lungs.

Question 15

Giev 2 examples of re-emergence of diseases.

Answer 15

1. TB and Diptheria- reduction in herd immunity over collapse of communism in russia.
2. Hospital acquired infections (HAI). Rise in antibiotic resistance. eg MRSA

Question 16

What is MRSA?

Answer 16

Methicillin resistant staphylococcus aureas. Danger in hospitals.

Question 17

What factors are responsible for emergence and reemergence of pathogens?

Answer 17

1. move to cities
2. transportatioin
3. economic development and change in land use
4. international travel
5. microbial adaption eg flu