Lecture notes
Disease Dilemmas Detailed Notes
- Module
- Disease Dilemmas
- Institution
- OCR
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1. GLOBAL PATTERNS OF DISEASESCLASSIFICATION
INFECTIONS = caused by microscopic germs such as bacteria/virus and can be spread by person or env
NON-INFECTIOUS = diseases which are not caused by pathogens such as scurvy, anaemia, diabetes, or cancer
COMMUNICABLE = disease can be spread from person to person in any form
NON-COMMUNICABLE (NCD) = also known as chronic diseases, are not passed from person to person. They
are of long duration and slow progression. There are 4 main types: cardiovascular disease, cancers, chronic
respiratory diseases, and diabetes.
CONTAGIOUS = infectious diseases that spread from person to person through contact
NON-CONTAGIOUS = disease not caused by touching infected
ZOONOTIC = infectious diseases that can transmitted from animals to humans such as ringworm or West Nile
Fever
ENDEMIC = Exist permanently in a geographical area or population group. EXAMPLE – sleeping sickness
confined to rural areas in sub-Saharan Africa and Chagas disease found in Central and South America which is
caused by small parasites transmitted by blood-sucking insects.
EPIDEMIC = An outbreak of a disease that attacks many people at the same time and spreads through a
population in a restricted geographical area. EXAMPLE – an outbreak of Ebola disease in West Africa in March
2014 led to an epidemic
PANDEMIC = An epidemic that has spread worldwide. EXAMPLE – Asian flu (1957-58) and Mexican flu (2009)
TYPES OF DIFFUSION – process of disease spreading outwards from origin
EXPANSION RELOCATION CONTAGIOUS HIERCHICAL
It has a source and When a disease leaves Spread of disease It spreads through an
spreads outwards into the area of origin and through direct contact ordered sequence of
new areas. Meanwhile, moves into new areas. with a carrier, strongly places, usually from the
carriers in the source EXAMPLE – cholera influenced by distance. largest center with the
area remain infected. epidemic in Haiti in 2010 EXAMPLE – the Ebola highest connectivity to
EXAMPLE – outbreak of which originated in epidemic in West Africa smaller more isolated
TB Nepal and was brought in 2015-15 centers.
to Haiti by international EXAMPLE – in 2009, the
aid workers flown in to H1N1 virus spread to
tackle the earthquake locations with
disaster that year. international airports
People taking flights
from one place to
another
,BARRIERS TO DIFFUSION
PHYSICAL SOCIO-ECONOMIC POLITICAL
Mountain ranges, seas, Housing conditions – high Political borders check the
deserts. Climate – major density international movement of
factor in epidemiology and Education programmes carriers of infectious
distribution of diseases. Employment – how much diseases. Imposing curfews
Distance from source. contact to limit contact with people,
Climate – some diseases Government does not have closure of public events,
more apparent in specific economy to back up such vaccination programmes.
climates such as malaria as affording vaccination Legislations – guidelines
programmes
HAGERSTRAND MODEL
Traces the diffusion process by imitating it with numbers.
The model is based on probability rather than fixed numbers
The model shows that the probability of contact between a carrier and a non-
carrier is determined by the number of people living within a 5×5km square =
neighborhood effect
The number of people infected by a disease over time follows an S-shaped curve
The process of diffusion can be stopped by physical barriers
GLOBAL VARIATIONS OF...
MALARIA HIV TUBERCULOSI DIABETES CVD
S
2021 – 247M 2021 – 38.4M 13 leading
th
The number of Leading cause
cases HIV cases. Of cause of death people with of death
worldwide and those, 36.7M and 2nd leading diabetes rose globally. 2019 –
619,000 were adults and infectious killer from 108M in 17.9M CVD
malaria deaths. 1.7M were after COVID. 1980 to 422M deaths, 32% of
The WHO under 15 years 2021 – deaths in 2014. all global
African Region and 54% were 1.6M. TB is Between 2000 deaths. Over ¾
has the highest women and present in all and 2019, there of deaths take
shares of the girls. This was a countries and was a 3% place in low-
global malaria 32% decline in mostly affects increase in and middle-
,cases, 95% of new HIV adults in their diabetes income
all malaria infections since productive mortality rates. countries. The
cases in 2021 2010. 650,000 years. Globally, 48% of all highest death
and 96% HIV related TB incidence is deaths due to due to CVD
malaria deaths. deaths in 2021 falling at about diabetes occurs in Asia
Some Most people 2% per year. occurred before and Africa with
population with HIV are in Over 80% of the age of 70. majority of
groups ae low- and cases and In lower- and countries
higher risk of middle-income deaths are in middle-income having over
contracting countries. 2/3 low- and countries, the 2,500 deaths
malaria such as of whom ae in middle-income mortality rates per 100,000 a
infants under 5, the WHO countries. due to diabetes year – Egypt
pregnant African region. People who are increased by had over 2,500
women and In 2021, 53% infected with 13%. 2021 – deaths per
patients with were in E and S HIV are 16 highest in W 100,000 in
HIV/AIDS. Africa, 13% in times more Pacific, 206M. 2019. The
COVID-19 W and Central likely to Followed by lowest death
disruptions led Africa, 15% in develop TB. In 90M in rate due to CVD
to about 13M Asia and the 2021, the Southeast Asia is in France of
more malaria Pacific and 5% largest number and 73M in 0-100 deaths
cases and in Europe and of new TB Middle East and per 100,000
63,000 more North America. cases occurred North Africa. ¾ people. Rates is
malaria deaths. in the WHO adults with lowest in AC’s
Four African South-East diabetes live in such as
countries Asia, with 46% low- and Australia and
accounted for of new cases, middle-income EDCs such as
just over half of followed by countries. 6.7M Brazil.
all malaria 23% of new deaths due to
deaths cases from the diabetes in
worldwide: WHO African 2021.
Nigeria, Region.
Democratic Rep
of Congo,
United Rep of
Tanzania, and
Niger
TEMPERATURE and DISEASES
- Temperature – affects rates of vector development and behavior - pathogens may
survive better in some conditions – viral replication
- Rainfall – flooding leads to spread of water borne diseases like cholera
- Sunlight – Tundra link to vitamin D deficiency – weaken immune system
- Impact on food production – malnutrition and undernutrition leading to lack of
vitamins leading to illnesses
- Warmer temperatures increase transmission of vector-borne disease up to the
optimum point, before slowing.
- Different vectors such mosquitos are adapted to a range of temperatures. Malaria
is most likely to spread at 25C while the zika virus is 29C
, PRECIPITATION and DISEASES
- Weaker immune systems during winter leading to an increase is seasonal diseases
such as the flu which is likely to develop around 5C
- Link to holidays so higher chance of relocation diffusions
- Lack of seasons leading to stability in climate may hinder or prolong diseases
- Seasonal precipitation also creates aquatic habitats such as stagnant pools which
allow insects and vectors to flourish
RELIEF and DISEASES
- Physical barrier to disease diffusion
- Lower population density leading to lower transmission of communicable diseases
- Malaria is concentrated in humid lowlands, water body adjacent, but absent in the
cooler highlands
WATER and DISEASES
- Some diseases are dependent on a water body - cholera
- Contaminated water due to natural disasters leading to an increase spreading of
diseases
- Contamination of supply which a high population uses – higher proportions of LIDC
populations reliant on water wells, or surface supplies
- Bodies of water are breeding grounds for bacteria and habitats for disease vectors
such as copepod vectors which transmit Guinea worm to humans
PHYSICAL FACTORS INFLUENCING VECTORS OF DISEASES
- Mosquitos in warm, humid areas close to water sources create more suitable
conditions for vector breeding to occur more quickly as eggs hatch faster in hotter
conditions. Higher humidity creates ideal conditions for malaria mosquitoes to
thrive.
- Natural barriers such as physical body such as skin mucus, or geographical barriers
such as mountain ranges or large bodies of water
- Amount of rainfall which can either cause drought or flooding leading to
waterborne diseases
- Climate change causing global temperature change allowing vectors to move into
previously uninhabited areas
SEASONAL VARIATIONS INFLUENCING DISEASE OUTBREAKS
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