Lecture 14: Theory & Science of disease Flashcards
What is a disease?
A disorder of structure or function in a human, animal, or plant, especially one that produces specific symptoms or that affects a specific location and is not simply a direct result of physical injury.
Non‐communicable diseases
A disease that is not transmitted through contact with an infected or afflicted person.
Non-communicable diseases are spread by heredity, surroundings and behavior.
Communicable diseases
An infectious disease transmissible (as from person to person) by direct contact with an affected individual or the individual’s discharges or by indirect means (as by a vector).
Communicable
Sleeping sickness Cholera Dengue Hepatitis Ebola HIV/AIDS Influenza Common Cold Malaria Measles Meningitis Polio Typhoid Yellow Fever Tuberculosis Zika
Non‐communicable
Heart disease Cancer Diabetes Hypertension Alzheimers Osteoporosis
Infectious diseases
Any infection, usually transmitted by insects–eg, ticks–eg, Lyme disease, Rocky Mountain spotted fever, ehrlichiosis, Colorado tick fever; mosquitoes– eg, California‐or La Crosse, St Louis, Eastern, Western encephalitides
Vector
A carrier, especially the animal (usually an arthropod) that transfers an infective agent from one host to another.
Examples of vectors
An organism, such as a mosquito or tick, that carries disease‐causing microorganisms from one host to another.
Human biting rate =
The number of bites by vectors per human per day
Entomological Innoculation Rate (EIR) =
Number of infectious bites received per person per year
Vector competence =
the ability of the vector to acquire, maintain and transmit pathogens
Basic reproductive number: R0
The number of cases one case generates on average over the course of its infectious period, in an otherwise uninfected population.
Helps determine whether or not an infectious disease can spread through a population.
The larger the value of R0, the harder it is to control an outbreak.
Disease risk maps
- Without unlimited cash, time, resources, we really can’t measure disease everywhere…
- Plus ‐ things change = unlimited cash, time, resources every year….?
- Governments, aid agencies, international health bodies, doctors, scientists need some information on the distribution of disease risks.
Global scale:
– WHO: situation, progress made, target areas, efficient resource use, numbers at risk
– Funding agencies/Government donors: efficient allocation, impact measurement
– Scientists: impacts of socioeconomic, environmental changes, causes of disease
– Medical profession: travel advisory, imported case estimation
Who needs maps??
• National scale:
– Governments: resource allocation, health system planning, monitoring progress
– Aid agencies: funding allocation, impact assessment
– Scientists: impacts of socioeconomic, environmental changes, causes of disease
