WEEK 2: CONTROL OF COMMUNICABLE DISEASES Flashcards
Define the following:
- Control.
- Elimination
- Eradication
- Extinction
Control: the reduction of disease incidence, prevalence, morbidity or mortality to a locally acceptable level as a result of deliberate efforts; continued intervention measures are required to maintain the reduction.
Elimination: Reduction to zero of the incidence of a specified disease in a defined geographical area as a result of deliberate efforts: continued intervention measures are required.
Eradication: Permanent reduction to zero of the worldwide incidence of the disease; intervention measures are no longer needed
Extinction: The specific infectious agent no longer exists in nature or in the laboratory
State the top 10 causes of death in Botswana.
- HIV and AIDS
- ischemic heart disease
- Stroke
- Lower respiratory tract infection
- Diabetes
- Diarrheal diseases
- TB
- Neonatal disorders
- COPD
- Alzheimer’s disease
In order for disease to occur there needs to be interaction between these variables.
State the 3 variables of the epidemiological triad.
Agent, Host, Environment
What is the chain of transmission?
The process by which an infectious agent leaves its host or reservoir (through a portal of exit), is conveyed by some mode of transmission and enters a susceptible host (through a portal of entry).
What is incubation period?
It is the period between the entry of the organism and the appearance of the first symptom of the disease.
What is knowledge of the incubation period important for?
*Surveillance and quarantine in some diseases
*Application of preventive measures to abort or modify the attack.
*Identification of the source of infection
What is a reservoir?
Habitat in which infectious agent normally lives, grows and multiplies.
May or may not be the source from which the agent is transferred to a host (e.g., Clostridium botulinum)
Human Reservoirs may or may not show effects of illness.
Describe the following:
Asymptomatic/healthy/passive carriers
Incubatory carriers
Convalescent carriers
Chronic carriers
Asymptomatic/Healthy/Passive Carriers:
Asymptomatic Carriers: These individuals are infected with a disease-causing microorganism but do not exhibit any symptoms of the disease.
Healthy Carriers: Similar to asymptomatic carriers, healthy carriers do not experience any symptoms of the disease, but they are carriers of the pathogen.
Passive Carriers: This term can be used interchangeably with asymptomatic carriers and healthy carriers. It refers to individuals who are carrying the microorganism without exhibiting signs of the disease.
Incubatory Carriers:
Incubatory carriers are individuals who have been exposed to an infectious microorganism and are in the incubation period of the disease. During this period, the microorganism is multiplying within their body, and they are not yet symptomatic. However, they can still transmit the pathogen to others.
Convalescent Carriers:
Convalescent carriers are individuals who have recovered from an infectious disease but continue to carry the pathogen for some time after their symptoms have resolved. During the convalescent period, they may still be able to transmit the microorganism to others.
Chronic Carriers:
Chronic carriers are individuals who continue to carry a pathogen for an extended period, often for the rest of their lives, without ever fully clearing the infection.
They may not exhibit symptoms or may have intermittent symptoms. Chronic carriers are particularly important in the transmission of diseases where the microorganism can persist in the body over the long term, such as certain viral and bacterial infections like hepatitis B and tuberculosis.
Animal reservoirs.
How does transmission occur?
Zoonosis: Transmission under normal conditions from vertebrae animals to humans.
*Touching them
*Eating uncooked products of animals.
State environmental reservoirs.
Soil (e.g., histoplasmosis)
Water (e.g., Legionella)
What is the portal of exit?
Path through which pathogens leave host.
Often correspond to site of where they are localized.
There are 2 modes of transmission: Direct and indirect. Give examples of each.
- Direct
Direct contact
Droplet spread - Indirect
Airborne
Vehicles
Vectors
Susceptible host is the final link in chain of infection.
What does susceptibility depend on?
Genetic factors
Specific immunity
Non-specific factors
What are the 4 factors that are considered when deciding on priority diseases?
- Impact
- Epidemiological potential
- Potential for prevention and control
- International importance
Describe the chain of TB transmission.
Caused by M tb (Mycobacterium Tuberculosis)
- (5 microns diameter)
Particles can be suspended in the air for several hours.
Cough, sneeze, talk by infected person.
Inhalation of droplet nuclei by susceptible host.
The TB chain of transmission is a cascade in which (1) a source case of TB.
(2) generates infectious particles
(3) that survive in the air and
(4) are inhaled by a susceptible individual
(5) who may become infected and
(6) who then has the potential to develop TB.
