Disease Dilemmas SG1 Flashcards
Define Infectious
A disease caused by a pathogen such as bacteria, virus, parasite or fungus
Define Contagious
Spread from person to person
Define Communicable
Spreadable host to host (host may be insect, animal or human), may or may not be contagious
Define Non-Communicable
Any disease which can’t be spread between people because it is non-infectious and non-contagious, it is caused by lifestyle
Define Zoonotic
Infectious diseases transmitted from animals to humans
Define Endemic
Disease which is permanently found within a particular geographical area e.g. Malaria
Define Epidemic
Large number of people with the same disease within a defined geographical location e.g. Ebola
Define Pandemic
Worldwide spread of an epidemic e.g. HIV
What is malaria classified as?
Infectious, communicable, non-contagious
What causes malaria?
The Plasmodium Falciparum parasite is spread by the Anopheles mosquito, if the mosquito bites a human the parasite enters the bloodstream and travels to the liver
What happens if a mosquito bites a person already infected with malaria?
It can become infected and spread the parasite on to other people
What is the distribution of malaria?
Occurs mainly along the equator and in the southern hemisphere, Mostly in South America, Central Africa and Asia
What % of the worlds population is at risk from malaria?
50% - 95 countries
In areas of what altitudes and rainfall does malaria transmission decrease?
Altitude over 1,500m and rainfall below 1,000mm
What is HIV classified as?
Infectious, communicable, contagious
What causes HIV?
Spreads between people through bodily fluids, unprotected sex, sharing contaminated needles and unsafe blood transfusions
What is the distribution of HIV?
Significantly varies across the globe, High proportions in sub-Saharan Africa
What is diabetes classified as?
Non-infectious, non-communicable, non-contagious
What causes diabetes?
Lifestyle or genetics
What are the two types of diabetes?
Type 1 - can’t produce insulin
Type 2 - smoking, lack of activity, diet
What is the distribution of diabetes?
High concentration in developed countries e.g. North America, High in China, Russia and Brazil
Why is diabetes mainly found in developed countries?
They have more choice over lifestyle and it is rising in lower to middle income countries as they have a lack of funding or awareness
What is tuberculosis classified as?
Infectious, communicable, contagious
What causes tuberculosis?
A bacterial infection spread by the transmission of mycobacterium tuberculosis from person to person through the air, due to sneezing and coughing
What is the distribution of tuberculosis?
High distribution in poorer areas, New cases in sub-Saharan Africa (especially near the equator), High in Southern Africa
What % of deaths from tuberculosis are in low-middle income countries?
95%
What are three reasons for the distribution of tuberculosis?
Poor living conditions in poorer communities (e.g. high population density, poor ventilation), Limited access to health services, Higher where immune system already compromised e.g. due to HIV or malnutrition
What is cardiovascular disease (CVD) classified as?
Non-infectious, non-communicable, non-contagious
What causes CVD?
Combination of lifestyle factors (e.g. diet, smoking), lack of exercise, aging population and population density
What is the distribution of CVD?
Eastern Europe, Middle East and sub-Saharan Africa has the highest number of cases, High rates in ACs but lowest mortality due to it
What % of 17 million deaths in LIDCs is due to CVD?
80%
Define Disease Diffusion
The process by which a particular disease spreads outwards from its geographical source
Define Expansion Diffusion
Occurs when a disease spreads from one place to another, often intensifying in the originating region and weakening in new areas e.g. H1N1 in Mexico
Define Relocation Diffusion
A spatial spread process whereby a disease leaves the area it originated in and moves to another e.g. SARS
Define Contagious Diffusion
Spreads due to direct contact between people e.g. cholera outbreak on Broad Street (1852)
Define Hierarchical Diffusion
Spread of disease through an ordered sequence of classes or places e.g. HIV or Ebola
What was Hagerstrand’s Model designed to stimulate?
The spread of farm subsidies in South Sweden but later applied to contagious diffusion of a disease
What is Concept 1 of Hagerstrand’s Model?
There was a Neighbourhood Effect
What is the Neighbourhood Effect?
The probability of contact between a carrier and non-carrier is determined by the number of people living in each 5x5km square and their distance apart
Who has a higher probability of contracting a disease, according to the Neighbourhood Effect?
People living in close proximity to carriers compared to those located further away
What is a limitation of the Neighbourhood Effect?
Today it is limited because we travel more, meaning people living further away can get the disease
What is Concept 2 of Hagerstrand’s Model?
The number of people infected by an epidemic approximated an S-shaped or Logistic Curve over time
What are the four steps of Hagerstrand’s S-shaped curve?
Primary, Expansion, Condensation, Saturation
Define Primary Step
There is a strong contrast in disease incidence between the area of outbreak and more remote areas
Define Expansion Step
Diffusion is centrifugal - new centres of disease outbreak occur at distance from the source which reduces the spatial contrast of the primary stage
Define Condensation Step
The number of new cases is more equal in all locations, irrespective of the distance from the source
Define Saturation Step
Diffusion decelerates as the incidence of the disease reaches its peak
What are two limitations of Hagerstrand’s S-shaped curve?
Assumes every disease behaves in the same way, Doesn’t show what happens when people begin to tackle the disease
What is Concept 3 of Hagerstrand’s Model?
The progress and diffusion of disease may be interrupted by physical barriers
What are five examples of physical barriers to diffusion?
Climate, Mountains, Oceans, Deserts, Distance
What are seven examples of socio-economic barriers to diffusion?
Curfew, Quarantine, Masks, Cancelling public gatherings, Vaccinations, Education, Political borders/check points
Define Vectors
Living organisms that can transmit diseases between humans or from animals to humans
What are six physical factors influencing the vector of malaria (mosquitoes)?
Precipitation, Seasonal variation in precipitation, Temperature, Relative humidity (RH), Relief, Water sources
How does precipitation affect the prevalence of malaria?
Female Anopheles mosquitoes lay their eggs in stagnant water, e.g. puddles. Areas with >1,000mm annual rainfall have a higher number of cases
How does seasonal variation in precipitation affect the prevalence of malaria?
Relatively sudden transmission of P.Falciparum occurs where seasonality is most marked e.g. at the end of the monsoon season the ground is saturated so more puddles for mosquitoes to lay their eggs in
How does temperature affect the prevalence of malaria?
Where average temperature is 18-40 degrees C the mosquitoes take more blood meals which increases the number of eggs laid. Larvae develop faster at higher temps, so parasites have more time to complete their lifecycle
How does relative humidity (RH) affect the prevalence of disease?
Where average monthly RH is >60% (influenced by vegetation growth) the mosquitoes have a better chance of survival and become more active
How does relief affect the prevalence of disease?
Mosquitoes can’t survive in cold temperatures, Places in Ethiopia >2,000m are too cold for P.Falciparum to develop in the mosquito vector
How does water sources affect the prevalence of disease?
More stagnant (non-flowing) water e.g. puddles makes ideal conditions for mosquitoes to lay their eggs
What % of people will become vulnerable to malaria due to a 2-3 degree C increase in temperature?
5% (several hundred million people)
How does climate change cause malaria to threaten regions of South America, sub-Saharan Africa and China?
50% higher transmission of malaria
How many more cases of malaria in under 15 year olds could result from a 1 degree increase in temperature?
3 million
When was anthrax released from the thawing permafrost in Siberia?
2016
How many reindeer died due to the anthrax outbreak in Siberia?
2,300
When was the first case of cholera reported near the Latem River in Mirebalais
12th October 2010
When was MSPP alerted of unusually high numbers of cholera from the Artibonite?
19th October 2010
When did St. Marc in the Artibonite River Delta report an explosive outbreak of cholera?
20th October 2010
When was the first case of cholera reported in Port-au-Prince?
9th September 2010
How long had it been in Haiti since the last cholera outbreak before 2010?
Over 100 years - low levels of immunity, unaware of the disease, no understanding of symptoms or treatment
What % of Port-au-Prince’s 2 million residents lived in densely populated slum areas
86%
When did troops from Nepal set up camp in Meille?
October 8th 2010
Why did the Red Cross deliver water?
There was no running water in the camps created after the earthquake for 1.5 million people
What % of rural Haitians had access to an improved water source before the outbreak?
51%
What % of rural Haitians had access to improved sanitation in 2010?
10%
Why were environmental conditions near optimal for an outbreak of cholera in Haiti?
Incidences of cholera peak when the air temperature reaches 26 degrees C and following heavy periods of rain, After the earthquake Haiti experienced above average warm air temperatures and anomalously high rainfall
How many people were infected with cholera in Haiti?
700,000 people - 7% of population
How many deaths resulted from the cholera outbreak in Haiti?
10,000
Why was there distrust of the UN?
They introduced cholera to Haiti but wouldn’t take responsibility for it
Why were victims of cholera in Haiti buried in mass graves?
To prevent the spread of disease - led to families not knowing where relatives were buried
Why were there higher death rates from cholera in rural areas of Haiti?
Poor road networks and few health centres made it difficult to access health care
What are four examples of strategies by the UN to minimise the impacts of cholera in Haiti?
Appeal for US$160 million, 680 rapid responses to cholera alerts in all 10 departments, Providing vaccines to >50,000, Provided 160,000 households with water treatment products
What are three examples of strategies by the UK government to minimise the impacts of cholera in Haiti?
Supply >1,000 trained medical staff and emergency supplies, Fund 115 doctors, 920 nurses and 740 support staff to set up 12 major cholera treatment centres, £2m of funding to Pan American Health Organisation
What are two examples of strategies by the Red Cross to minimise the impacts of cholera in Haiti?
Sanitation services and fresh water supplied daily
What are three examples of strategies by Oxfam to minimise the impacts of cholera in Haiti?
Mix chlorine solution with drinking water for local communities, Educating on how to prevent cholera, Built new latrines
What are three examples of strategies by Doctors Without Borders to minimise the impacts of cholera in Haiti?
Built a 400-bed tent hospital, Created makeshift reservoir, Offer purification drops for people who want it
What are two examples of strategies by Partners in Health to minimise the impacts of cholera in Haiti?
Psychologists work with people affected, Set up treatment centres
What are four examples of strategies by MSPP and CDC to minimise the impacts of cholera in Haiti?
Establish a national cholera surveillance system to monitor the spread, Provided Haitian news outlets with five basic prevention messages advising on how to protect from cholera (in 3 languages), Trained health workers who then went on to train 1,100 more people in mainly rural communities, Supplying Oral Rehydration Solution (ORS) sachets
In November 2019, for many months had there been no laboratory confirmed cases of cholera in Haiti?
9 months
