L2: General Epidemiology of Communicable Diseases

Question 1

Def of Infection

Answer 1

Entry, development &/or multiplication of the infectious agent in the body of man or animal.

Question 2

Depending on factors in both host and organism; Infection results into either:

Answer 2

• A clinically manifest disease (Infectious disease). Or
• The presence of infection without recognizable clinical signs or symptoms and identifiable only by laboratory means (Inapparent infection-subclinical infection).

Question 3

Def of Infestation

Answer 3

The lodgment, development and reproduction of a parasite on the body surface or inside body tissues

Question 4

Def of Contamination

Answer 4

The presence of an infectious agent on a body surface, in clothes, bedding, toys, surgical instruments or dressings, or other inanimate articles or substances including water and food.

Question 5

Def of Communicable disease

Answer 5

• An illness due to a specific infectious agent or its toxins that arises through transmission from an infected person, animal or inanimate reservoir to a susceptible host.
• It may be either directly or indirectly

Question 6

Def of Latent Infection

Answer 6

• Infectious agent lies “dormant” within the host without clinical manifestations.
• It reactivates under certain conditions causing the disease.

Question 7

Ex of agents with Latent Period

Answer 7

herpes zoster, Pulmonary tuberculosis

Question 8

Def of Opportunistic infection

Answer 8

Nonpathogenic agents, cause disease when host immunity decreased

Question 9

Examples of Opportunistic infection

Answer 9

Pneumocystis carinii, Toxoplasma, CMV

Question 10

Def of Zoonotic infection

Answer 10

• An infection or infectious disease transmissible under natural conditions from vertebrate animals to humans

Question 11

what is World Health Organization (WHO)?

Answer 11

• A part of the United Nations that deals with major health issues around the world.
• The World Health Organization sets standards for disease control, health care, and medicines; Conducts education and research programs; and publishes scientific papers and reports.
• The headquarters are located in Geneva, Switzerland.

Question 12

WHO Regions

Question 13

International Health Regulations (IHR)

Answer 13

Question 14

Public health Emergency of International Concern (PHEIC)

Answer 14

Question 15

The WHO should be notified if …….

Answer 15

Question 16

Types of occurrences and spread (distribution) of infectious diseases in communities

Answer 16

• Sporadic
• Cluster
• Endemic
• Epidemic
• Outbreak
• Pandemic

Question 17

Sporadic Spread

Answer 17

The infrequent and irregular occurrence of a disease (without common source of infection)

Question 18

Cluster Spread

Answer 18

The aggregation of cases grouped in place and time.

Question 19

Endemic Spread

Answer 19

• The constant presence of an infectious disease within a given geographic area.
• It may also refer to the usual prevalence (baseline level) of a given disease within such area

Question 20

Endemicity of a disease is determined by ……

Answer 20

the existence of its ecological factors (agent, host and environment)

Question 21

Epidemic

Answer 21

• An increase in the number of cases of a disease above what is normally expected in that population in that area.
• The number of cases indicating epidemic varies according to the infectious agent, size and type of population and time and place of occurrence.

Question 22

Epidemic threshold

Answer 22

• The critical number or incidence above which an urgent measure is required to control the emerging epidemic.
• Each disease has a specific threshold that depends on its infectivity, transmissibility and the degree of endemicity in a locality.

Question 23

Outbreak

Answer 23

Epidemic in limited geographic area or confined group.

Question 24

Pandemic

Answer 24

Epidemic that spreads over several countries or continents (Epidemic that crosses international borders)

Question 25

trends of occurrence of infectious diseases

Answer 25

The occurrence of disease changes over time, Some of these changes occur regularly, while others are unpredictable.

Question 25

Epidemics, outbreaks or pandemics occur when

Answer 25

Question 26

Secular trends

Answer 26

Some diseases show long term variation in the occurrence.

Question 27

Seasonal trend

Answer 27

- Some diseases such as influenza and West Nile infection are known to have characteristic seasonal distributions. - Seasonal patterns may suggest hypotheses about how the infection is transmitted, what behavioral factors increase risk, and other possible contributors to the disease or condition.

Question 28

Day of week and time of day trend

Answer 28

In conditions related to occupational or environmental exposures that tend to occur at regularly scheduled intervals.

Question 29

Epidemiologic weeks

Answer 29

Question 30

Natural History of Disease

Answer 30

It is the progress of a disease in an individual over time in absence of intervention.

Question 31

The outcome of any infection depends on two opposing forces:

Answer 31

1. Invading organism: Dose, pathogenicity, virulence. 2. The host: Body resistance and immunity.

Question 32

Chain of infection (infectious cycle)

Answer 32

Question 33

Def of **Infectious agent**

Answer 33

An organism (virus, bacteria, fungus, protozoa or helminth) that is capable of producing infection or infectious disease.

Question 34

Agent factors that affect disease behavior

Answer 34

- Infectivity - Pathogenicity - Virulence - Antigenicity (Immunogenicity) - Resistance

Question 35

what is Infectivity?

Answer 35

Ability of agent to produce infection (invade, survive and multiply) in a susceptible host

Question 36

What is Infectivity measured by?

Answer 36

- Measured by the secondary attack rate (Proportion of exposed susceptible who become infected). - Secondary attack rate = (Number of secondary cases ÷ Number of exposed susceptible) x 100.

Question 37

what is **Pathogenecity**?

Answer 37

- Ability of the organism to produce overt clinical reaction after infection.

Question 38

What is **Pathogenecity** Measured by?

Answer 38

- Measured by the ratio of clinical to subclinical case.

Question 39

What is **Virulence**?

Answer 39

- The degree of pathogenicity of an infectious agent.

Question 40

What is Virulence measured by?

Answer 40

- Ability of organism to produce severe pathological reaction (death or irreversible damage). - Measured by case fatality rates. - Case fatality rate = (Total number of deaths from a disease / Total number of cases of that diseases) X 100.

Question 41

What is **Antigenicity (Immunogenicity)**?

Answer 41

- Ability of organism to produce specific immunity (antibodies). - Measured by rate of occurrence of a second attack.(Re infection).

Question 42

What is **Resistance** of an agent?

Answer 42

The ability of the agent to survive adverse environmental conditions.

Question 43

Environmental resistance of Agents

Answer 43