1a Disease Intro Flashcards
Disease definition
Any harmful deviation from the normal structural or functioning state of an organism
Diffusion definition
The process by which diseases spread outwards from their origin
Communicable definition
An infectious disease transmissible from person to person by direct content with an affected individual; the individuals discharge or indirect means (such as a vector)
Non communicate disease
Also known as chronic diseases
Diseases not passed person to person.
Characterised by long duration and slow progress.
The 4 main types are CVDs, cancers, chronic respiratory diseases and diabetes
Contagious definition
A class of infectious disease which are easily spread by direct contact (e.g. sharing of bodily fluids) or indirect contact (e.g. coughing)
Non-contagious definition
Not spread by contact; normally require a special mode of transmission (such as vectors) or by non casual transfer of bodily fluid (such as blood transfusions or sharing needles)
Epidemic definition
Often sudden increase of a disease above what is normally expected in a population. The disease attacks many people at the same time and spreads through a population in a restricted geogrpahical area
Endemic definition
A disease which exists permanently in a geographic area or population group. Examples include sleeping sickness, confined to rural areas if sub Saharan Africa
Pandemic definition
An extensive epidemic - a pandemic is more widespread occurrence of a new disease affecting many countries or continents.
Classification of Malaria
Infectious
Non contagious
Communicable
Endemic
Epidemic
Classification of HIV
Infectious
Contagious
Communicable
Endemic
Pandemic
Classification of cholera
Infectious
Contagious
Communicable
Endemic
Epidemic
Classification of Ebola
Infectious
Contagious
Communicable
Endemic
Epidemic
Expansion diffusion
Disease spreads out from source in all directions from point of origin
Diffuses outwards into a nearby vicinity
Carriers in the source area remain infected
Expansion diffusion example
TB in East Asia
Clustering of some of the 22 high burden countries which account for 80% of all TB cases
Relocation diffusion
Disease spreads into new areas leaving the origin of the disease behind.
Disease is not contracted in areas between source and new area.
Disease dies out in previous location
Relocation diffusion example
Cholera in Haiti originated in Nepal
Brought over by aid workers after the 2010 earthquake
Contagious diffusion
Disease is spread through direct contact
Individual hosts carrying the disease pass it on to new contacts
Strongly influenced by distance (distance decay)
Contagious speeds tend to occur in a centrifugal manner from the source region outwards
Contagious diffusion example
Ebola in West Africa 2014-15
Hierarchical diffusion
Disease spreads down through a particular system
Disease spreads through an ordered system of classes or places, usually from the largest centres with highest connectivity to smaller more isolated centers
Diffusion is also channeled along road, rail and air transport networks which facilitate contact between carriers and susceptible populations.
Example of hierarchical diffusion
H1N1 started in Mexico city but spread to other large cities (NY, LA, Chicago( before contacted to smaller cities and rural towns.
2009
Mutation - antigenic shift
When two or more known strains of a virus combined to form a new strain
Time space compression
globalisation resulting in distances between places appear to contract because of changes like ease of transport and communication between these placed de to increased global connectivity . This allows diseases to spread more quickly.
Hägerstand model of diffusion
4 steps: primary step, expansion step, condensation step and saturation step.
Shows the unequal case load and diffusion rate across time and how a pathogen spreads.
Can be applied to Ebola in Liberia 2014/15
Herd immunity definition
When a high percentage of the population is protected through vaccination against the virus or bacteria making it difficult for a disease to spread because there are so few people susceptible left effect.
Neighbourhood effect
The probability of contact between the carrier and non carrier is determined by the number of people living in a 5 km x 5 km area, and their distance apart.
People living in proximity do carriers have a greater probability of contracting the disease than those further away
