Epidemiology Of Infectious Diseases

Question 1

What is an infection

Answer 1

An infection is said to occur when micro organisms (viruses, bacteria etc) invade and multiply in the body.

Question 2

What is contamination?

Answer 2

Contamination is the presence of a constituent, impurity or any undesirable element that spoils, corrupts, infects, makes unfit or make inferior the physical body, material, natural environment, workplace etx

Question 3

What is a disease?

Answer 3

Disease is defined as harmful deviation from the normal structural and functional state if an organism, generally associated with signs and symptoms and different in nature from physical injury.

Question 4

What’s the triad of infection?

Answer 4

Agent
Host
Environment

Question 5

What’s an incubation period?

Answer 5

Incubation period is the time from initial invasion of infectious agent to onset of the disease.

Question 6

What are the Determinants of incubation period?

Answer 6

1. State of immunity of an individual
2. Pathogenicity - ability of the organism to cause disease
3. Microbial load
4. Location - part of the body involved

Question 7

Differentiate between pathogenicity and virulence

Answer 7

Pathogenicity is the ability of the organism to cause a disease.

Virulence is the ability of the disease to kill.

Question 8

Highlight significance of incubation period

Answer 8

1. Prognosis determination
2. Quarantine
3. Contact tracing
4. Vaccine development
5. Epidemic control - is achived when there is no new case after 2 incubation periods of the disease.
6. mgt of the disease

Question 9

What are the two disease with no mode of exit?

Answer 9

Tetanus and dracunculiasis

Question 10

What are the modes of transmission?

Answer 10

1. Direct - no vehicles
2. Indirect - vehicles are used e.g food, water, vector

Question 11

What’s carriership?
What are the types of carriership?

Answer 11

Carriership is the ability to transmit infectious agent without manifesting the disease.

Types
1. Incubatory carriership - transmit agent during incubation period. E. G Hep. B, HIV, measles

2. Convalescent carriership - transmit agent after or during manifestation of the disease e.g typhoid

Question 12

How do you treat a typhoid carrier?

Answer 12

A typhoid carrier should be treated with antibiotics for 14days.

Question 13

How is a typhoid carrier treated?

Answer 13

A typhoid carrier should be treated with antibiotics for 14days because Salmonella typhi is stored in the urinary and gall bladders.

Question 14

What’s are the ways in breaking chain of transmission?

Answer 14

1. Increase immunity if the host.
2. Reduce susceptibility
3. Eliminate/reduce vehicles
4. Destroy breeding site of agents.

Question 15

What are the criteria for isolation?

Answer 15

A patient is only isolated if the disease has the following:
1. High infectivity
2. High virulence
3. No extra human reservoir

Question 16

Differentiate the following epidemic, endemic, pandemic and outbreak.

Answer 16

EPIDEMIC: occurrence of a disease in excess of what is expected if that population at that given time.

ENDEMIC: Regular occurrence of a disease at all times in a particular place.

PANDEMIC: An epidemic across atleast two countries in 2 different continents. i.e global epidemic.

OUTBREAK: occurrence of a disease in excess of what is expected of that population over a SHORT period of time. i.e Short epidemic.

Question 17

What are the types of outbreak?

Answer 17

Common source outbreak
Propagated source outbreak

Question 18

What’s the difference between point source and continuous source?

Answer 18

Point source: outbreak is from the same source and at the same time. People contact it at same time

Continuous source: outbreak is from same source but at different times. They contact it at different time.

Question 19

Differentiate b/w common and propagated source.

Answer 19

Common source: outbreak is from the same source.

Propagated: source is not the same.

Question 20

What is median time on a point source outbreak curve?

Answer 20

The time when 50% of people manifest signs and symptoms of the disease/infection.

Question 21

Who is a primary case?

Answer 21

The first person to bring infection (in propagated source outbreak)

Question 22

Using formula, diff btw attack rate and secondary attack rate.

Answer 22

ATTACK RATE = no.of new cases divided by
No of susceptible persons, multiply by 100

Question 23

Differentiate btw attack rate and secondary attack rate.

Answer 23

Attack rate is not a good measurement of spread.
In attack rate, primary case is involved.
Attack rate is useful in common source outbreak.

SAR is a good measurement of spread.
It does not include the primary case.
It is useful in propagated outbreak

Question 24

Ways to reduce SAR

Answer 24

Immunization of people to reduce susceptibility.
Chemoprophylaxis

Question 25

Outline the steps in investigation of disease outbreak

Answer 25

1. Verify diagnosis
2. Verify there is an epidemic.
3. Open register for cases identified. Tools in identifying cases: spot map, epidemic curve, case control study
4. Immunize control to reduce susceptibility.
5. Treat all cases.
6. Communicate the factors to the people.
7. Write a report of the epidemic and it’s intervention.
8. Surveillance.

Question 26

What is surveillance?

Answer 26

Surveillance is continuous watchfulness of factors responsible for the spread of a disease. This is achieved through data collection