Module 4 Flashcards
Endemic
The habitual presence of a disease within a population
Epidemic
The occurrence in a community or region of a group of illnesses of similar nature, clearly in excess of normal expectancy and derived from a common or propagated source
Pandemic
A worldwide epidemic
Single-exposure, common vehicle outbreak
When all cases of an outbreak come from a single source (e.g., food) and people are exposed only once
Herd immunity
The resistance of a group of people to an attack by a disease to which a large proportion of the members of the group are immune
Incubation Period
The interval from the receipt of infection to the time of onset of clinical illness
Attack Rate
Number of people at risk in whom a certain illness develops/Total number of people at risk
This is useful for comparing the risk of disease in groups with difference exposures
Disease arises from an interaction of…
Host
The agent
The environment
A vector may also be involved
Human susceptibility
is determined by a variety of factors, including genetic background, behavioral, nutritional, and immunologic characteristics
What are the modes of disease transmission
Direct: person-to-person
Indirect: common vehicle or a vector
Virulence of the Organism
How efficient the organism is at producing disease
Clinical disease
Characterized by signs and symptoms
Non clinical Disease Classifications
Preclinical disease: a disease that is not yet clinically apparent but is destin to progress to clinical disease
Subclinical: Disease that is not clinically apparent and is not destine to become clinically apparent
Persistent: A person fails to shake the infection, and it persists for years, at times for life
Latent disease: An infection with no active multiplication of the agent
Carrier status
A person who harbors the organism but is not infected as measured by serologic studies or shows no signs of clinical illness (also called asymptomatic or presymptomatic)
What are the types of common vehicle exposures
single exposure
multiple exposure
periodic
continuous
What are the characteristics of common-vehicle outbreaks?
They are generally explosive
The are limited to the people who share the common exposure
In the case of food-borne outbreaks - they rarely occur in persons who did not eat the food
What conditions have to exist for herd immunity to exist
- The disease agent must be restricted to a single host species
- The transmission must be relatively direct
- infections must induce solid immunity (not partial)
- operates optimally when populations are constantly mixing
- the % of the population that must be immune varies depending on the disease
Incubation period
The interval from receipt of the infection to the time of onset of clinical illness
Latency period
The incubation period for noninfectious diseases
Epidemic curve
the distribution of times of onset of the disease
In a single exposure, common vehicle epidemic, the epidemic curve represents the distribution of the incubation periods
What are the three critical variables in exploring disease
- Who was attacked by the disease
- When did the disease occur
- Where did the cases arise
Secondary attack rate
the attack rate in susceptible people who were not exposed to the suspected agent who have been exposed to the primary case
What are the three critical variables in investigating an outbreak or epidemic?
When did the exposure take place
When did the disease begin
What is the incubtaion period for the disease
What is R0 (R Not
It is the basic reproduction number of an infection. It is a RATIO not a rate. And it can be thought of as the expected number of cases directly generated by one case in a population where are individuals are susceptible
The average number of new infections generated by each infected person
