Disease
Dilemmas
What are the global patterns of diseases and how can factors be identified that
determine these?
Key Term Definition Example
Infectious Liable to be transmitted to people, organisms, etc. through the Influenza, Malaria
environment. Diseases caused by bacteria or viruses.
Non-Infectious A disease not liable to be transmitted through the environment. Cystic Fibrosis,
Cardiovascular
Disease
Communicable Transmissible and highly infectious. Aids, Cholera
Noncommunicabl A disease that is not transmissible directly from one person to Cancer, Heart
e another. Disease.
Contagious A class of disease easily spread by physical contact. Ebola, Yellow
Fever.
Non-contagious Not spread by contact.
Epidemic A widespread occurrence of an infectious disease in a Ebola
community at a particular time.
Endemic A disease native to a certain place. Chicken Pox
Pandemic A disease prevalent over a whole country or the world. Covid-19, Spanish
Flu
Global distributions of diseases:
Malaria:
Malaria is an infectious but noncontagious equatorial disease. It thrives in warm, humid and wet conditions
across flat and rural land. Malaria is often found around areas with high concentrations of stagnant water.
Malaria is prevalent in Ethiopia, Madagascar and DRC Congo. Areas at high risk are Southern Mexico and
Southern India. Malaria is not found in the UK, Australia or South Africa.
HIV:
HIV is prevalent across the whole world, however, is highly concentrated in central and southern Africa. This
is due to high levels of bush meat consumption. In 2015, 35 million people had HIV worldwide. For Example,
more than 20% of South Africans have HIV/AIDS and 10% of Nigerians live with HIV. Less than 0.1% of the
population in the UK and Madagascar have HIV. There are no cases in the UBE or Greenland.
Tuberculosis:
TB affects 9 million people worldwide. It is a highly contagious disease spread through livestock and wildlife.
TB is highly prevalent where there are overcrowded living conditions. 95% of people who die of TB live in
LIDCs and EDCs. The UK, US and France have relatively low cases at 0-24 cases per 100k people whereas
Russia, Ethiopia and Chile have 100-299 cases per 100,000. Greenland has zero cases.
Cardiovascular Diseases:
CVD accounts for 17 million deaths a year worldwide. CVDs are usually caused by lifestyle choices. The
number of cases usually rise with age in ACs. Mortality Rates per 100,000: UK, France, US= 120-238, India,
DRC= 363-443, Russia, Middle East= 444-861.
Disease Spread:
Distance Decay:
The number of new cases of a disease is affected by distance. Places closer to the source are more likely
to see more cases. Areas further away are less likely to be affected.
Hagerstand’s neighbourhood effect:
1) Primary Step- Small population is infected.
2) Expansion Step- Spreads rapidly and exponentially.
3) Condensation Step- It has infected most of the population however, some people are still infected.
4) Saturation Step- Herd immunity stage.
These models are probabilistic rather than deterministic.
4 types of disease diffusion:
Expansion:
One place of origin. The disease spreads out however remains in the same place overtime. For Example,
Spanish Flu which killed an estimated 40 million people within a few months.
Contagious:
Contagious disease diffusion is spread by contact with the source. The diseases’ influence is strongest at the
place of origin and the influence lessens as you get further away. For Example, the 1852 cholera outbreak in
Broad Street, London.
, Hierarchical:
This type is spread through a class or group of people and could happen where something spreads around one
city and then spreads around another city. For Example, HIV/AIDs in San Francisco which then spread to major
cities such as New York, LA and then spreads to smaller cities.
Relocation:
The disease that is spreading around one place then moves to a new region (there is a jump/leap in location).
For Example, a relocation of Cholera in Haiti in 2010 was brought in via aid workers from Nepal.
All 4 of these types of diffusion can combine, known as Mixed Diffusion. This occurred with the spread of HIV.
What is it:
Severe Acute Respiratory Syndrome is a viral respiratory caused by a Corona Virus.
Symptoms:
Fever, Body Aches, Headaches and occasionally diarrhoea.
How does it spread?
Expansion diffusion: close person to person contact via tiny droplets.
SARS management:
Isolation, Social Distancing
Police were deployed to survey the public in Hong Kong.
Toronto Health identified close contacts and towns were isolated.
International Efforts:
UN (WHO)- Global Outbreak Alert and Response Network.
Closation of borders.
Covid-19 vs SARS:
China’s outward travel has doubled since 2008.
Number of people living in cities has tripled.
Covid-19: 5 million people had travelled and left china before alerts.
SARs symptoms instant and Covid symptoms are asymptomatic in 1/3 of people.
Ebola 2014 Outbreak Case Study
What kind of disease is Ebola?
Ebola virus (EVD) is a serious viral infection that affects most commonly affects people and nonhuman
primates (such as monkeys, gorillas, and chimpanzees). Ebola is considered an emerging infectious disease.
Ebola is a communicable disease. Communicable diseases, also known as infectious diseases or transmissible
diseases, are illnesses that result from the infection, presence and growth of pathogenic (capable of causing
disease) biologic agents in an individual human or other animal host.
Ebola virus was first discovered in 1976 near the Ebola River in what is now the Democratic Republic of
Congo. Since then, the virus has been infecting people from time to time, leading to outbreaks in several
African countries. Scientists do not know where Ebola virus comes from. Based on similar viruses, they
believe EVD is animal-borne, with bats or nonhuman primates being the most likely source. Infected animals
carrying the virus can transmit it to other animals, like apes, monkeys, duikers and humans.
The virus first spreads to people through direct contact with the blood, body fluids and tissues of animals.
Ebola virus then spreads to other people through direct contact with body fluids of a person who is sick with
or has died from EVD. This can occur when a person touches these infected body fluids or objects that are
contaminated with them. The virus then gets into the body through broken skin or mucous membranes in the
eyes, nose, or mouth. People can get the virus through sexual contact with someone who is sick with or has
recovered from EVD. The virus can persist in certain body fluids, like semen, after recovery from the illness. 2
Ebola Symptoms:
2
Symptoms may appear anywhere from 2 to 21 days after contact with the virus, with an average of 8 to 10
days. The course of the illness typically progresses from “dry” symptoms initially (such as fever, aches and
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