DD Overview fact file

What is the difference between an infectious disease and a contagious disease?

Infectious diseases are spread by pathogens (e.g. bacteria and viruses), mostly from direct contact from one person to another.

Contagious diseases are a type of infectious disease that is spread by both direct and indirect contact between people, this could be airborne or by contact with a surface where secretions have been left

State 3 causes of infectious diseases

• Bacteria

• Viruses

• Parasites

What is an endemic disease? Give an example

A disease that is permanently located in a geographical area or a population group e.g. Sleeping Sickness is endemic in rural sub-Saharan Africa

What is the difference between an epidemic and pandemic?

Epidemics affect many people at the same time but are restricted to a population in a geographic area, whereas a pandemic disease is spread worldwide

What is a disease vector? Name one

A disease vector is a disease carrier or intermediate host e.g. Anopheles mosquito that transmits malaria

Name 3 ways in which diseases can diffuse across space

• Expansion diffusion spreads outwards from an origin e.g. TB in a shanty town or waterborne disease spreading via poor sanitation

• Relocation diffusion occurs when a disease leaves its area of origin and moves to new areas e.g. Cholera originating in Nepal was relocated by aid workers to Haiti

• Contagious diffusion describes the spread of disease through direct contact with a carrier e.g. Ebola in West Africa

State 2 factors which facilitate disease diffusion and are barriers to disease diffusion

Routeways and insanitary conditions facilitate disease diffusion, mass vaccination programmes and distance are barriers to disease diffusion

What is meant by the epidemiology of a disease?

Epidemiology is the study of the causes, effects, distribution and controls of a disease in a population

Why are natural hazards often accompanied by outbreaks of disease?

Natural hazards, such as EQs or tsunamis, see sanitation systems breakdown leading to the spread of waterborne diseases from the contamination of drinking water. Medical help is disrupted and any controls preventing the spread of disease collapse. A population becomes much more susceptible to disease when their nutrition and access to clean drinking water are compromised; those already vulnerable because of a poor diet, and consequent compromised immune system or because they have never been vaccinated are the most at risk in the shorter term

How does an ageing population affect the incidence of non-communicable diseases?

Non-communicable diseases are those that cannot spread between people, such as genetic defects or cancer. As a population ages so do the prevalence of age related diseases.The more developed regions of the world, AC’s are those where age related illnesses are more prevalent e.g. heart failure, pulmonary disease and diabetes

Outline 2 environmental factors that are linked causally to communicable hosts

Communicable diseases are infectious and spread from host to host. A lack of proper sanitation or poor hygiene mean there is potential for contamination of food and water supplies and the spread of water-borne and bacterial diseases. Poor drainage provides a breeding ground for disease vectors such as mosquitoes and water snails which transmit diseases like malaria

What aspects of lifestyle are associated with the incidence of CVD and cancer?

Lack of exercise combined with an unhealthy diet lead to obesity which increase the risks of both CVD and cancer. Smoking is the single biggest single cause of cancer and is also a major risk factor for CVD

What is the epidemiological transition?

Credited to Abdel Omram, the epidemiological transition suggests there is a relationship between development and changing patterns of population age, mortality, fertility, life expectancy and causes of death. These changes are driven by improvements in health care, standards of living and the quality of the environment. He identified 3 stages: ‘the age of pestilence and famine’ in pre-industrial societies; ‘the age of receding pandemics’ in industrial societies where conditions are improving, and ‘the post-industrial society’ where infectious diseases are rare but age related diseases and cancer become more common. A 4th stage has also been suggested where medical advance delays degenerative diseases

What is the difference between undernutrition and malnutrition?

Too little food intake to maintain body weight is described as undernutrition, while malnutrition is the result of an unbalanced diet, especially where there is a shortage of proteins and essential vitamins

How does overnutrition contribute to disease?

Where there is prolonged excessive intake of food, particularly diets high in fat, sugar and salt, the bodies weight increases as does the risks of CVD, type 2 diabetes, hypertension and some cancers

Name 3 diseases caused by lack of essential vitamins

• Rickets from vitamin D deficiency

• Scurvy from vitamin C deficiency

• Pellagra from vitamin B deficiency

Name a disease caused by a protein deficiency

Kwashiorkor

Outline the epidermiology of malaria

The malaria parasite passes between 2 hosts, the Anopheles mosquito and people. Infected female Anopheles mosquitoes feed on blood as they breed and in so doing transmit the parasite plasmodium into a person they are feeding from. The parasite reproduces in the human living inducing chills, sweats, fever, muscle pain, nausea, and vomiting within 7 to 30 days. These symptoms occur as merozoites (next stage of the cycle) bursts out of the liver into the blood stream. The merozoite is then able to infect the next mosquito that feeds from a person with malaria

> Anopheles mosquito is generally limited to tropical and sub-tropical locations where it is warm and moist enough for the species to breed. Anopheles larvae need still/ stagnant water in which to breed

Describe the geography of malaria in Ethiopia

Malaria is endemic to much of Ethiopia, however it is not evenly distributed within the country. Tigray, Amhara and Gambelle provinces in the western lowlands have the highest risk particularly between June and November after the rainy season. The midlands have only occasional epidemics; and to the east where it is drier, malaria is only found along the rivers. The central highlands, one quarter of Ethiopia, are malaria free

Why are irrigation schemes often accompanied by a rise in the incidence of malaria?

Irrigation creates stagnant surface water which is an ideal breeding ground for mosquitoes

Describe 3 strategies that can be used to control malaria

1. Spraying dwellings with insecticides to kill mosquitoes

2. Insecticide treated bed nets prevent mosquitoes from biting, which they mostly do at night

3. Destroying breeding sites by removing stagnant water, or destroying the surface tension of water with drops of oil, kills mosquito larvae

How can lifestyle choice affect the incidence of cancer?

Smoking is the biggest single lifestyle choice that causes cancer in men and women. Sunbathing and the use of sun beds increases the risks of skin cancer. Unhealthy food choices including processed foods increases the risk of bowel cancer. Over recommended consumption of alcohol increases the risks of oral oesphageal and liver cancers. Lack of exercise and dietary choices has given rise to an obesity epidemic which also increases the risks of several types of cancer

Explain the relationship between socio-economic deprivation and cancer rates

There is a well-established link between cancer rates and socio-economic deprivation. Where deprivation rates are high there is an increases likelihood of smoking, high alcohol consumption and obesity. All are major causes of cancer. The most deprived areas of Britain are coincident with some of the highest cancer rates. Cancer survival rates similarly are linked to socio-economic deprivation as a result of pre-existing health status and speed of diagnosis

What can be done to improve cancer survival rates?

Direct strategies include investment in medical technology to aid diagnosis and treatment. Waiting times have been reduced between GP referral and specialist consultants, and therefore between diagnosis and treatment. Screening for bowel and cervical cancers have improved survival rates; teenage girls are given vaccinations for HPV (Human Papolloma Virus) which is set to reduce the incidence of cervical cancers. Cancer research has seen increased investment from fundraising, and this has improved understanding of the disease alongside the development of new treatments

Indirect strategies are aimed at lifestyle changes and cancer prevention. Education and health campaigns advocating healthy lifestyles and informing the public of the dangers of smoking, excessive drinking and poor diets are helping reduce the incidence of preventable cancers

Suggest 2 reasons for the current epidemic of skin cancer in the UK

The current preference fro a ‘tanned look’ has led to increases in sunbed use Increased wealth has led to longer holidays and increases in sunbathing both at home and abroad. With affordable package holidays to sunny locations we ‘cook in the sun’ in relatively short holidays, leading to burning and skin damage at cellular (DNA) level

State 2 possible causes of cholera outbreaks

Cholera is a waterborne disease that can accompany insanitary conditions where drinking water is contaminated by sewage. Cholera is a bacterium that can be passed on where there is poor sanitation and consequent personal hygiene, something often found in overcrowded conditions. Poor maintenance alongside overstretched water treatment infrastructure where populations are growing rapidly can also lead to contamination of drinking water

How does climate affect the incidence of malaria?

Malaria needs warm and moist conditions for the Anopheles mosquito to breed. It has been confined to tropical and sub-tropical locations, but as the climate warms and precipitations levels increase so the incidence of malaria is likely to spread

Why are flu epidemics most likely to occur in winter?

Current theories suggest we spend more time indoors in winter and are therefore in contact with more people. Another line of thinking suggests that we have less Vitamin D in our systems, something our bodies create when exposed to sunlight, which is though helps boost our immune system. In the northern hemisphere, between October and March, we are unable to manufacture vitamin D from the weak sunlight we are exposed to.

Recent research suggests that turning on the heating in winter dries the air that we breathe and it is thought that flu viruses thrive in dry air

Why has the threat of pandemics increased in the past 30 or 40 years?

In the past, isolation has protected communities from disease outbreaks, or contained a disease without it being able to spread far. In the past 30-40 years as incomes rise and the cost of travelling decreases, we have become much more mobile, with people commuting large distances daily and many of us travelling abroad much more often. The worldwide number of daily flights means that within 24 hours, a disease could circumnavigate the world. SARS (Severe Acute Respiratory Syndrome) travelled to 37 countries in a matter of weeks in 2003

Why do disease outbreaks often occur following natural disasters such as EQs and floods?

Natural hazards, such as EQs and floods, see sanitation systems breakdown leading to spread of waterborne diseases from the contamination of drinking water and faecal-oral transmission due to poor hygiene. Distribution of medical help is disrupted and any controls preventing the spread of disease collapse. A population becomes much more susceptible to disease when their nutrition and access to clean drinking water are compromised; those already vulnerable because of a poor diet, and consequent compromised immune system are the most at risk in the shorter term

What emergency steps can be taken to prevent the global spread of disease?

The World Health Organisation (WHO) has responsibility for monitoring and coordinating responses to health crises on a global scale work closely with other international organisations to prevent the global spread of disease. The WHO gathers health data from across the world, giving an insight into health risks. It also funds research into health issues and takes a leading role in raising awareness.

Gathering and dissemination information between governments, international agencies and aid organisations meant that during the Ebola crisis, there was a coordinated response.

The monitoring of a traveller’s body temperature meant that those with early symptoms who has come from countries with Ebola, were picked up and stopped from flying or isolated in special units in their own country. In the first decade of the 20th century, SARS and H1N1 saw many across the Asian continent wear face masks in the anticipation that it would prevent airborne disease transmission.

Governments have also recently, again, issued advice to bird/fowl owners to keep their flocks indoors to prevent spread of the bird flu virus from migrating birds.

How can physical barriers help prevent the spread of disease?

Physical barriers (such as mountain ranges, areas of rainforest or water bodies) often isolate communities and restrict population movement. Remoteness can be an advantage, reducing the risk of infection and spread of disease

How can physical barrier hinder the control of a disease outbreak?

Diseases that occur in isolated communities can delay the arrival of medical assistance and emergency aid. Where there is little immunity, diseases can quickly become fatal without outside assistance and render them more difficult to control/ contain. Natural hazards, such as flooding, can isolate an area preventing medical aid reaching a community

What preventative measures can be taken to control the spread of HIV/ AIDS?

The HIV virus is spread through the transmission of bodily fluids such as blood and semen. The modification of high risk behaviour needs public understanding through education programmes, for example, publicising the dangers of sharing needles and promoting safe sex helps people protect themselves. Promoting the human rights and equality for groups most at risk from HIV/ AIDS- women, girls, gay men, migrant workers and refugees- helps reduce discrimination and encourages these groups to access health programmes

What is mean by disease eradication?

Removal of a disease globally

Name the 3 diseases targeted by the UN in 2000 for eradication

• Polio

• Guinea worm

• Yaws

What are the advantages of grass-roots disease eradication campaigns compared with top-down campaigns?

Empowering local people, especially women (men often work away from home) means that communities are much more likely to engage with a project than one controlled by governments and international agencies. There is often a distrust and memory of corruption/ mismanagement within a community of top down projects that have failed; local control creates a sense of ownership and is much more likely to succeed

Why are many new drugs for treatment of major diseases so expensive?

For a leading pharmaceutical company to develop and test new drugs is a long and costly process. Huge investment in research and development means that for each new drug that is created, many others will fail. Recouping these huge costs and continuing to pay (and attract) the best researches comes from the sale of new patented drugs. Profits are the main driver of all transnational companies and pharmaceutical companies are no different. A patent generally lasts for 20 years in order to prevent cheap copycat versions from coming onto the market and allow the company to profit from their investment and continue researching into other drugs

Explain why the availability of generic drugs is so important in LIDCs

Generic drugs are identical to a brand name drug in all respects but without the cost associated with a patented brand. Low costs generic drugs increase availability and affordability, key factors in helping meet the needs of LIDCs

What steps can transnational pharmaceutical companies take to make patented drugs more affordable?

Some pharmaceutical companies, including GSK, have recently adopted more ethical approaches towards the developing world. There is a commitment by some TNCs to a smaller (5%) profit/ return on a range of products; discounted prices have been agreed with some nations for HIV/AIDS drugs along with the granting licences for cheap generic versions of some patented drugs. There are examples of capping the price of some patented drugs to 25% of the UK price, and investing 20% of the profit from sales to a developing nation into that countries health infrastructure