Lecture 6: Infectious Disease Flashcards
What are Sporadic diseases?
Occasional cases occurring at irregular intervals
What is an Endemic disease?
Continuous occurrence at an expected frequency over a certain period of time and in a certain geographical location
What is an Epidemic or outbreak?
Occurrence in a community or region of cases of an illness with a frequency clearly in excess of normal expectancy
What is a Pandemic?
Epidemic involves several countries or continents, affecting a large population
What are Special Features of an infectious disease epidemiology?
A case of disease may also be a risk factor (even if not recognised as a case)
Immunity can occur
Speed of intervention can be critical
Define Infectious agent/ pathogen?
A viral, bacterial, protozoan or fungal substance that causes disease.
Define Infection?
The entry and development or multiplication of an infectious agent in the body – the result may or may not be apparent.
Define Infectious Disease= Communicable Disease
An illness due to a specific infectious agent or its toxic products that arises through transmission of the agent/ products to a susceptible host.
What is the meaning of contagious?
Transmitted by contact
What Happens Following a Disease Notification?
Tracing contacts of the index case infected person to:
a) identify source of the infection
b) prevent further dissemination, e.g. tuberculosis
Interviewing affected people to identify the source of infection, e.g. in foodborne poisoning case
Confirming the diagnosis by further testing the infected person, e.g. measles
What Criteria Would You Use to decide Whether a Disease Should Be Notifiable?
Effectiveness Prevalence and severity of disease Possibility of source and contact tracing Derived risks for vaccination policy International consequences Feasibility Workload Possibility of diagnosis Necessity Subsidiarity Privacy
What are the direct transmission routes?
Mucous to mucous membrane Across placenta Transplants, blood Skin to skin Sneezes, cough
What are the indirect transmission routes?
Waterborne Airborne Food borne Vector borne Object/Fomites
What is a vector?
An insect or living carrier that transports an infectious agent from an infected individual or its wastes to a susceptible individual or its food or its immediate surroundings.
What is Biological transmission?
Transmission of the infectious agent to susceptible host by bite of blood feeding vector, or by other inoculation.
What is Mechanical transmission?
Transport of the infectious agent between hosts by arthropod vector with contaminated mouthparts, antennae, or limbs. There is no multiplication of the agent within the vector.
What is the Extrinsic Incubation Period?
Time necessary after acquisition of infection by the vector for the infectious agent to multiply or develop sufficiently so that it can be transmitted by the vector to the vertebrate host.
What is the Chain of Transmission?
The spread of infection from a source to a susceptible host is referred to as the chain of infection
What are the stages of the Chain of Transmission?
Link #1: The Pathogen
This is the disease-causing organism. For many illnesses and diseases this is a virus or bacterium.
Link #2: The Reservoir
This is the natural environment that the pathogen requires for survival. Reservoirs can be a person, an animal, or an environmental component, such as soil or water. Link #3: The Portal of Exit
This link is needed for the pathogen to leave the reservoir. Link #4: The Means of Transmission
The pathogen can be transmitted either directly or indirectly. Link #5: The Portal of Entry
Entry of the pathogen can take place in one of three ways: penetration, inhalation, or ingestion.
Link #6: The New Host
Once in the new host, various factors influence the severity of infection, including the strength of the immune system
What is the Epidemiological Triad?
The Epidemiological Triad describes the interaction between the agent, host and environment, which create the conditions for the transmission of infectious agents.
