Differences Between Diseases And Pathogens Biology Essay


The term 'disease' refers to any abnormal condition of an organism that impairs function. This causes discomfort, dysfunction, distress, or death to the person afflicted or those in contact with the person.

Infectious disease is disease caused by a pathogen which enters the body and triggers the development of an infection. Infectious diseases have a range of causes, and they can be found all over the world. These diseases are considered contagious or communicable, meaning that they can be passed from person to person. It is also possible for such diseases to spread indirectly through unhygienic conditions, or from animals to people, in which case they are known as zoonotic diseases.


Most pathogens are infectious microbes, such as bacteria or viruses, which are capable of causing disease. Other parasites, such as fungi and protozoans, are also considered pathogens. Because not all microbes are harmful, pathogens refer specifically to those that can cause disease or other harm.

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Task 2


Diagram of the organism Polio


Life cycle

Polio is an infectious disease that has haunted the lives of many for over 3,000 years. The first record of Poliomyelitis in the human body dates back to ancient Egypt where inhabitants of the area engraved a documented version of paralytic Poliomyelitis into stone. When indoor plumbing came into use, in the 20th century, and sewage systems began to develop into complicated public works where waste was dumped into towns' water supplies Poliomyelitis began to spread. The disease causing organism, Poliomyelitis, spread throughout the world and threatened lives for decades. It is recommended that a childhood vaccine is given in order to prevent the RNA based virus. Efforts have been made to eradicate the disease world wide, but doctors have not completely conquered the virus.

The life cycle of Polio is described as lytic. The lytic life cycle is a five-step process where a virus invades a host cell, in this case the Polio virus receptor (PVR). The procedure begins when the virus attaches itself to the host cell. The virus, using its tail fibres, attaches itself to a receptor site, a familiar place for a virus to attach itself. In the second stage of the lytic cycle, the viral DNA is released into the cell after an entrance is created. No actual hole is made in the cells surface; however, an enzyme, having been released from the virus, weakens a specific spot so that the viral DNA can be forced through and into the cell. After changing the cell's makeup so that proteins are synthesized differently, a translation process results in viral proteins and enzymes, as well as the replication of the viral DNA from the bacteria that is hosting the virus. Once the new viruses have been successfully assembled they are released through a process known as lysis. Lysis is a phase of the lytic cycle in which a newly created enzyme causes the disintegration of the cell.

Method of infectious spread

Polio virus is a very contagious virus that can spread easily from person to person. When a person is infected with polio virus, it is expected that polio transmission among susceptible household members will occur in nearly 100 percent of children and over 90 percent of adults.

Polio virus only infects humans, and it is more common during summer months in temperate climates. In tropical climates, there is no seasonal pattern. The polio virus is rapidly inactivated by heat, formaldehyde, chlorine, and ultraviolet light.

Symptoms of disease caused

There are many symptoms of polio and not everyone will experience all of the symptoms. They symptoms vary according to the type of polio the individual has. In mild polio, some of the symptoms are: headache, nausea, vomiting, general discomfort or a slight fever for up to three days. In nonparalytic polio (aseptic meningitis): the symptoms are similar to mild cases, with the addition of moderate fever, stiff neck and back, fatigue and muscle pain. The symptoms for polio and paralytic polio are different. Individuals with paralytic polio experience tremor, muscle weakness, fever, stiffness, constipation, muscle pain and spasms, and difficulty swallowing.

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Currently, there is no treatment for polio that can kill the polio virus. Antibiotics or other medications for polio are not effective because polio is caused by a virus. Therefore, treatment for polio focuses on providing relief of polio symptoms as the body fights the polio virus. This is called supportive care.

Supportive care as treatment for polio will depend on the symptoms of polio that a person experiences. For those with mild symptoms or aseptic meningitis, supportive care may include:


Medications (such as acetaminophen or ibuprofen) to control fever or pain

Rest until the fever improves.

In these cases, after 2-10 days, polio symptoms will usually have faded completely.

If paralytic polio occurs, treatment may be more extensive and long-term. Depending on the severity of symptoms, treatment for polio can include:

Medications to reduce pain and improve strength

Antibiotic medications for bacterial infections

Breathing assistance with a mechanical ventilator.


Polio is rapidly disappearing from significant areas of the world. When the global polio eradication goal was set in 1988, approximately 35 000 cases of polio were reported world-wide. In 1995, that number had fallen to 7000, an 80% decline. Many cases of polio are not reported, it is estimated that the reported total represents only 10% of the cases that actually occur.

India has reported more than half the world's polio cases every year. As a result of its first National Immunization Days (NID) - 93 million children were immunized in a single day in January 1996 - it appears that there will be a 70% decline in reported polio cases in India. Polio was eradicated from the Western Hemisphere in 1991; the last case was a 3-year-old boy from Peru. Polio is disappearing from Western and Central Europe, North Africa, Southern and Eastern Africa, the Arabian Peninsula and the Pacific Rim of Asia, including Australia. Polio in China has gone from 5,000 cases in 1990 to 3 imported cases in 1996. Eradication is close in the remainder of World Health Organization WHO's Western Pacific Region.

Economic importance

Polio cases have decreased by over 99% since 1988, from an estimated 350 000 cases in more than 125 endemic countries then, to 1997 reported cases in 2006. In 2008, only parts of four countries in the world remain endemic for the disease - the smallest geographic area in history.


Diagram of the organism tuberculosis (TB)


Life cycle

TB is a disease that can cause a serious illness and can damage a person's

organs. Every year more than 25,000 people in the U.S. are diagnosed with TB

disease. That's only a fraction of the amount of people who carry the

Mycobacterium tuberculosis. Mycobacterium tuberculosis is a rod-shaped

bacterium. TB is spread through the air by carriers of the bacteria. People who

breathe the same air can become infected with TB. TB infection

means that the person has the TB bacteria but it is in an inactive state. When

TB bacteria enter the body, the immune system builds a wall around them. While TB

bacteria are inactive, they cannot cause any damage. The bacterium can stay alive

for many years in these walls and eventually break out. At this time TB is

active and is known as TB disease. It can now affect the person's organs. A

person can have TB disease shortly after being infected if their immune system is weak.

TB can attack any organ of the body. The lungs are the most common area of

attack. People with the TB disease have one or more of the following symptoms:

a persistent cough, fevers, weight loss, night sweats, constant fatigue, and

loss of appetite. A person with the TB disease in the late stages will produce

Blood streaked sputum. People who have Active TB disease usually only have mild

symptoms. There are three tests to diagnose TB disease. One is the Tuberculin

Mantoux PPD skin test; two is a Chest X-ray which is given after the skin test

is positive; the third a Sputum Test reveals if TB bacteria are present in the thick liquid a person coughs up. The Tuberculin Mantoux PPD skin test is given by placing a substance

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called PPD Tuberculin under the top layer of the skin with a very small needle

and syringe. The doctor will inject the needle into the skin which will only

feel like a slight pin prick. A few days later the skin test reaction will be

read by a trained health professional. If the skin around the prick is raised and it

is bigger or the same size as a pencil eraser then the person is likely to have

been infected with TB. This does not mean he or she has TB disease.

Inactive and Active TB can be treated in various ways. People who may come into contact with people who have Active TB should take precautions.

Although a person infected with the TB bacteria may not have the TB disease this could develop later in life without appropriate medication. The medication can destroy the bacteria before they become active. A person with inactive TB and other illnesses which weaken their immune system should especially take medication to prevent TB disease.

A vaccination has been developed to prevent TB infection however this is unproven. The vaccination is routinely given to teenagers.

Method of infectious spread

Tuberculosis (TB) is caused by a strain of bacteria called mycobacterium tuberculosis.

TB is spread when a person with an active infection of TB in their lungs coughs or sneezes, and somebody else inhales a droplet of contaminated saliva. However, despite being spread in the same way as a cold or the flu, TB is not as contagious.

To contract TB a person would need to spend a prolonged period of time with an infected individual. The infection is usually spread amongst members of the same household. It is highly unlikely that the infection would be contracted by sitting next to an infected person on a bus or train.

Symptoms of disease caused

Tuberculosis (TB) will not cause any symptoms until the infection has reached the lungs. As the bacteria are very slow moving, symptoms might not develop for many years after the initial exposure to the bacteria has taken place.

A TB infection of the lungs is known as pulmonary tuberculosis.

Symptoms of pulmonary tuberculosis include:

a persistent cough that brings up phlegm (thick mucus), which may be bloody,

breathlessness: symptoms of breathlessness are usually mild to begin with before gradually getting worse,

weight loss,

lack of appetite,

fever: a temperature of 38°C (100.4°F) or above,

fatigue, and

A general sense of feeling unwell.


Pulmonary TB is treated using a six-month course of a combination of antibiotics. The usual course of treatment is:

two antibiotics: isoniazid and rifampicin (every day for six months), plus

Two additional antibiotics: pyrazinamide and ethambutol (for the first two months).

To prevent the TB infection becoming resistant to the antibiotics it is essential that the infected person completes the prescribed course accurately. The person who does not complete the course or misses doses is at risk of developing multi-drug resistant TB which can be challenging to treat.


World Health Organization (WHO) estimates that the largest number of new TB cases in 2008 occurred in the South-East Asia Region, which accounted for 34% of cases globally. However, the estimated incidence rate in sub-Saharan Africa is nearly twice that of the South-East Asia Region with over 350 cases per 100 000 population.

An estimated 1.3 million people died from TB in 2008. The highest number of deaths was in the South-East Asia Region, while the highest mortality per capita was in the Africa Region.

In 2008, the estimated per capita TB incidence was stable or falling in all six WHO regions. However, the slow decline in incidence rates per capita is offset by population growth. Consequently, the number of new cases arising each year is still increasing globally in the WHO regions of Africa, the Eastern Mediterranean and South-East Asia.

Economic importance

Tuberculosis threatens one-third of the world's population. The World Health Organization declared tuberculosis a global health emergency in 1993. The magnitude of the problem changed dramatically during the 1990s due to deteriorating control in some parts of the world (notably Eastern Europe and the former Soviet Union), the spread of HIV causing a suppressed immune system, and population growth. Without a coordinated control effort, tuberculosis will infect an estimated 1 billion more people by 2020, killing 70 million.


Diagram of the organism Thrush


Life cycle

Yeasts secrete enzymes that break down carbohydrates (through fermentation) to yield carbon dioxide and alcohol. The source of carbohydrates is either living hosts or non-living hosts such as rotting vegetation, or the moist body cavities of animals. Yeasts are considered by some scientists to be closely related to the algae, lacking only in photosynthetic capability-perhaps as a result of an evolutionary trend toward a lifestyle dependent upon host nutrition. Ecologically yeasts are decomposers that secrete enzymes which dismantle the complex carbon compounds of plant cell walls and animal tissues, which they convert to sugars for their own growth and sustenance. Yeast reproduction may involve sexual spore production or asexual budding, dependent upon surrounding conditions. Though yeasts are highly tolerant of environmental variations in temperature and acidity, they thrive in warm and moist places high in oxygen and low in carbon dioxide. Whether or not they reproduce through asexual budding depends on the favourability of surrounding conditions: when times are good, yeast clones are produced by budding. In times of environmental stress, yeasts produce spores which are capable of withstanding periods of environmental hardship-perhaps even to lie dormant, until conditions improve and the mingling of genes can take place with the spore of yeast.

Method of infectious spread

Thrush is caused by a naturally occurring fungus, usually Candida albicans. The fungus is often present in the mouth and vagina and, sometimes, it does not cause any symptoms.

There are a number of factors that have been associated with triggering episodes of thrush. However, with the exception of pregnancy, antibiotics, and poorly controlled diabetes, evidence for individual risk factors have been found to be inconclusive.

Symptoms of disease caused

Some people don't have any signs or symptoms, and may not be aware they have thrush. Sometimes thrush symptoms will be noticed during a vaginal examination for a cervical screening test.

Women might notice:

Itching, soreness and redness around the vagina, vulva and anus.

Unusual vaginal discharge which may be thin, thick and look like cottage cheese.

Pain on passing urine or during sex.

Men might notice:

Irritation, burning or itching under the foreskin or at the tip of the penis.

Redness or red patches on the penis or under the foreskin.

A thick or thin discharge, like cottage cheese, under the foreskin.

Discomfort when passing urine.

Oral thrush symptoms

White spots to develop in the mouth.

Sore, cracked, red areas just outside the mouth

Affected babies may drool saliva, or refuse to feed properly because of soreness.


You can only be certain you have thrush if you have a test. The test is simple and painless. It involves taking a swab to take a sample of cells from the vagina or penis. The vagina, penis and genital area will also be examined.

Treatment is very simple and involves using antifungal cream, medication or a combination.

If left untreated, it usually goes away, as the body can often fight off some infections naturally. However untreated vaginal thrush may trigger inflammation of the urethra in a male partner.


25 percent of infants develop thrush during the first 3 months of life. Thrush is extremely rare in adults. The availability of over the counter treatment may account for the reduced reporting of the infection in adults. Although it is rare in adults it is more common in those who have a weak immune system.

Economic importance

Although there is no economic importance to thrush, there are people that do have to miss days at work due to the infection, this could be down to themselves visiting the doctor or taking the day of because of a child. Days off work cost the economy, so therefore this is the only economic importance.


Diagram of the organism Malaria


Life cycle

This small single-cell organism has three to four different forms. Each form is specialised in living in a certain place.

The gametocyte is the form that infects the mosquito and reproduces itself, as if it were both sexes. When the mosquito has sucked blood containing gametocytes, these pass into the salivary glands of the mosquito, where they develop into a new form, the sporozoite. The infection can then move on.

The sporozoite can be passed on to man when the mosquito bites, injecting its saliva into the tiny blood vessels. The sporozoite travels with the blood to the liver and enters the liver cells. In the liver some of the sporozoites divide (tachysporozoites) and become thousands of merozoites.

The merozoites are released from the liver to the blood where they are taken up by the red blood corpuscles. Some of these turn into ring-formed trophozoites that split again to form schizonts.

Schizonts burst the red blood corpuscles at a certain moment, releasing the merozoites. This release coincides with the violent rises in temperature during the attacks seen in malaria.

The trophozoites that are left over during division can, in the course of the next day, develop into the sexual form, the gametocyte, which can be taken up by a blood-sucking mosquito and start another cycle.

The incubation period (time from infection to development of the disease) is usually about 10 to 15 days. This period can be much longer depending on whether any antimalarial medication has been taken.

Plasmodium ovale and Plasmodium vivax can produce a dormant form, a hypnozoite, that can cause relapses of the disease months and even years after the original disease (relapsing malaria) because it's dormant in the liver cells. This is why it's important after these infections to be treated with primaquine to kill the liver stages.

Method of infectious spread

The plasmodium parasite is spread by female anopheles mosquitoes. If a mosquito bites a person infected with malaria, it can then carry the parasite and spread it to other people after it has developed in the mosquito.

The parasite enters blood through a bite and travels to the liver, it then re-enters the blood stream and invades red blood cells.

Once in the red blood cells, the parasites grow and multiply. Eventually, the infected red blood cells burst and release even more parasites into the blood.

The infected cells usually burst every 48-72 hours. Each time this happens, an infected person will experience an attack of chills, fever and sweating.

The female mosquitoes usually bite between dusk and dawn and are known as night-biting mosquitoes.

Symptoms of disease caused

Symptoms of malaria usually appear 10-15 days after being bitten. However, it can take a year for symptoms to show dependant on the type of parasite the person is infected with.

Symptoms of malaria are similar to flu symptoms and include:

a high temperature (fever) of 38°C (100.4F) or above

sweats and chills

generally feeling unwell

muscle pains




With some types of malaria, fevers occur in 48-hour cycles. An infected person will feel cold at first with shivering for up to an hour. This is followed by a fever lasting between two and six hours with extreme sweating.


A blood test can identify malaria, this may be repeated due to varying levels of the malaria parasite found in blood. A person who has taken anti-malarial medication may have levels of the parasite which are too low to detect. Medication is available to treat malaria this can be specific to the part of the world the malaria was contracted in.


Malaria is a public health problem today in more than 90 countries, inhabited by a total of some 2,400 million people - 40% of the world's population. It is estimated that there are 300-500 million cases of the disease each year worldwide. More than 90% of all malaria cases are in sub-Saharan Africa. Mortality due to malaria is estimated to be 1.5 to 2.7 million deaths each year. The vast majority of deaths occur among young children in Africa, especially in remote rural areas with poor access to health services. Other high-risk groups are women during pregnancy, and non-immune travellers, refugees, displaced persons and labourers entering endemic areas. Malaria epidemics related to political upheavals, economic difficulties and environmental problems also contribute in the most dramatic way to death tolls and human suffering.

Economic importance

Malaria causes significant economic losses, and can decrease gross domestic product (GDP) by as much as 1.3% in countries with high levels of transmission. Over the long term, these aggregated annual losses have resulted in substantial differences in GDP between countries with and without malaria, particularly in Africa.

The health costs of malaria include both personal and public expenditures on prevention and treatment. In some heavy-burden countries, the disease accounts for:

up to 40% of public health expenditures;

30% to 50% of inpatient hospital admissions;

Up to 60% of outpatient health clinic visits.

Malaria disproportionately affects poor people who cannot afford treatment or have limited access to health care, trapping families and communities in a downward spiral of poverty.

Task 3A

Spread of pathogens

Pathogens can spread from person to person in a number of ways. Not all pathogens use all the available routes. For example, the influenza virus is transmitted from person to person through the air, typically via sneezing or coughing. But the virus is not transmitted via water. In contrast, Escherichia coli is readily transmitted via water, food, and blood, but is not readily transmitted via air or the bite of an insect.

While routes of transmission vary for different pathogens, a given pathogen will use a given route of transmission.

Another route of transmission is as a spore which is very small and light. A spore is able to float in air and can be breathed into the lungs. An example of this is anthrax in which the bacterium Bacillus anthracis forms a spore which on entry to the lungs resumes its growth and swiftly causes a serious and often fatal form of anthrax.

Contamination of water by pathogens is another insidious route of disease spread. Water remains crystal clear until there are millions of bacteria present in each millilitre. Viruses, which are much smaller, can be present in even higher numbers without affecting the appearance of the liquid. Water can contain large quantities of pathogens to cause illness examples of this are cryptosporidium and legionella.

Food borne pathogens cause millions of cases of disease and hundreds of deaths each year. Frequently the responsible microbes are bacteria, viruses, or protozoa that usually reside in the intestinal tract of humans or other creatures. Examples of micro-organisms include Escherichia coli, Campylobacter jejuni, and rotavirus.

Pathogens can be transmitted to humans through contact with animals, birds, and other living creatures that naturally harbour the micro-organism. The agent of anthrax-Bacillus anthracis-naturally dwells in sheep. Other examples include Brucella abortic (Brucellosis), Coxiella burnetti (Q fever), and viruses that cause hemorrhagic fevers such as Ebola and Marburg.

Personal hygiene.

Personal hygiene is the basic concept of cleaning, grooming and caring for our bodies. While it is an important part of our daily lives at home it is also important for worker health and safety in the workplace. Workers who pay attention to personal hygiene can prevent the spread of germs and disease, reduce their exposures to chemicals and contaminants, and avoid developing skin allergies, skin conditions, and chemical sensitivities.

The first principle of good hygiene is to avoid exposure by forming a barrier over the skin with personal protective equipment (PPE) such as gloves, aprons, and goggles. It is important to check the PPE often for excessive contamination and wear and tear. Workers should clean, decontaminate or replace protective equipment frequently to make sure it doesn't collect or absorb irritants. If protective equipment becomes too soiled during the job, the worker should stop and replace it with clean equipment.

Correct hand washing and skin care can prevent the spread of disease. The use of water and soap helps to remove germs, contaminants, and chemicals. It can also prevent exposure by ingestion and cross-contamination of the surfaces and objects touched.

Workers should periodically wash their hands during the day. In some jobs, regular hand washing is required by law. Hand washing is important before and after using the restroom and before or after certain activities. Workers should wash their hands before, during, and after preparing food and before they take breaks at work to eat, drink or smoke. To control the spread of germs that can cause the flu or common cold, workers should wash their hands whenever they cough, sneeze, or blow their noses, and whenever they are around someone that is sick.

Hand washing involves more than a quick rinse under a tap. To wash hands properly, workers should first wet them under the tap and then use liquid soap. Hands should be held out of the water until all skin surfaces are scrubbed and lathered for at least twenty seconds. Workers can then rinse with clean water and dry their hands with a disposable towel. To wash hands with a hand sanitizer, workers should apply the appropriate amount of sanitizer into the palm of the hand, and then rub hands together until they are dry, being careful to cover all surfaces of the hands. For some job activities, hand sanitizers are not an acceptable means of hand cleaning. Showering and face-washing after work is also a good idea.

Antiseptics role in the prevention of infection and the spread of infection

An antiseptic is a substance that inhibits the growth and development of micro-organisms. Antiseptics are either bacteriocidal (kills bacteria) or bacteriostatic (stops the growth of bacteria). Antiseptics can be topical agents applied to the skin, mucous membranes and inanimate objects. They can also be used internally such as urinary tract antiseptics. They can be used to cleanse skin and wound surfaces after injury, to prepare skin surfaces prior to injections or surgical procedures, and routine disinfection of the mouth. Antiseptics are also used for disinfection of inanimate objects including instruments and surfaces.

Task 3B

The spread of HIV is causing severe problems in some areas of the world, particularly Sub-Saharan Africa. Despite the advances in the medical treatment many problems still remain. Produce a case study which discusses

The medical problems, both short term and long term, caused by HIV infection

HIV stands for human immunodeficiency virus (HIV). The virus infects and gradually destroys immune system cells, reducing the body's protection against infection and cancers. In the short term this may make a person with HIV more susceptible to everyday illnesses such as colds. A person infected with HIV is infected for life - there's no cure.

Over time, as the immune system weakens, a person with HIV may develop rare infections or cancers. When these are particularly serious, the person is said to have acquired immune deficiency syndrome (AIDS).

The personal problems caused by HIV infection to sufferer & the social problems caused by HIV infection

From the moment scientists identified HIV, social responses of fear, denial, stigma and discrimination have accompanied the epidemic. Discrimination has spread rapidly, fuelling anxiety and prejudice against the groups perceived as most at risk of being affected, as well as those living with HIV. HIV causes both social and medical concerns.

The global HIV epidemic has triggered compassion and support amongst communities bringing out the best in people and their families.

However the disease is also associated with stigma, repression and discrimination. Individuals affected (or believed to be affected) by HIV can be rejected by their families, their loved ones and their communities. This rejection occurs in both rich and poorer countries.

Stigma is a powerful tool of social control within society. Social groups associated with HIV have been rejected by society, these include homosexuals, injecting drug users and sex workers. Society as a whole can relieve itself of the responsibility of caring for these groups by placing blame on the individual or group. People living with HIV can be seen as bringing shame upon themselves, their family and community and individuals infected can be punished. Incidents of violence and murder have been reported across the globe in relation to a persons HIV status. Being infected with HIV is seen as the result of personal irresponsibility in some societies. Negative responses to HIV can reinforce social ideals of proper behaviours in relation to sex and illness.

The stigmatisation of individuals affected by HIV is increased in some societies through the use of legislation. This can include compulsory screening and limitations placed on individuals with respect to international travel. The exclusive screening of groups considered to be high risk can cause a false sense of security amongst low risk groups.

The social problems experienced by individuals with HIV can impact on them personally through fear of victimisation if their HIV status becomes common knowledge. They could concerned as to how they will be seen as an employee or potential employee if seeking employment. A person with HIV may also fear rejection by their family and friends leaving them socially isolated. The stigma of HIV can leave a person anxious as to how they will be able to provide for their family.

A person with AIDS has a loss of income and increased spending on healthcare. The reduced household income leads to a reduction in spending. There can also be substitution of money away from education to cover healthcare and funeral expenses. A study in the Ivory Coast showed that households with a HIV/AIDS patient spent twice as much on medical expenses as other households.

The economic problems, both to the country and globally, caused by HIV infection

The incidence of HIV and Aids affects economic growth by reducing the availability of people fit to work. Large numbers of the population suffer and die from AIDS related illness due to the lack of adequate nutrition and health care compared to those living in developed countries. It is suspected that the economies of countries with a large population affected by HIV will collapse. As the illness progresses the individual will not be able to work and will require increased medical care. The HIV epidemic has left behind many orphans who are cared for by elderly grandparents or left to fend for themselves in some densely affected areas.

Globally the incidence of mortality from HIV and AIDS reduces the skilled population and workforce. A younger workforce with reduced knowledge and experience can lead to reduced productivity. Workers taking time off to care for sick family members or for sick leave themselves can also reduce productivity. AIDS can weaken the taxable population leading to a reduction in resources available for public expenditure. This can increase pressure on a countries finances and lead to slower economic growth.

Task 4 A

Natural immunity

Natural immunity occurs through contact with a disease. There are two types of natural immunity. Actively acquired and passively acquired.

Actively acquired occurs when the body has already been exposed to an infection by that pathogen

Passively acquired occurs when antibodies pass across placenta providing a newborn baby with immunity against disease. Antibodies are also present in breast milk.

Artificial immunity

Artificial immunity develops through deliberate action such as vaccine. There are two types: Actively acquired and passively acquired .

Actively acquired occurs when a vaccination is administered at a suitable time in the person's life, not when they are infected. e.g. TB vaccine.

Passively acquired occurs when a vaccine containing ready-made antibodies which provide immediate relief by destroying the antigens is administered. This is given when the person has been infected with the antigen and has no previous immunity e.g. tetanus.

Task 4 B

Explain how the antibodies formation occurs in the two following situation:

A young child exposed to chicken pox virus

Chicken pox is caused by varicella zoster virus (VZV). The virus enters the body by

breathing or touch, and moves through the body via the bloodstream. It can enter the dorsal ganglion cells of the sensory nerves and remain dormant there.

When a child is exposed to the virus it triggers an immune response in the body to destroy the virus. White blood cells (lymphocytes) known as B-cells and T-cells are rapidly produced in large quantities during the immune response. Killer T-cells destroy the virus by attaching to the virus and secreting chemicals. Antigens are present on the viral coat of the virus they stimulate the production of antibodies by B-cells. There are 2 types of B-cells known as memory cells and plasma cells. Plasma cells only live for a few days however they produce antibodies which can remain in the blood for a long time. The antibodies produced are specific to VZV antigens and can attach to the antigens and destroy them. Antibodies are proteins called immunoglobulin's which when produced remain in the person's body throughout their life time providing immunity. When a child has been exposed to VZV and has produced antibodies the body can respond to any further exposure by killing the virus before it develops into the disease. Antibodies present in the blood attack the virus while memory B-cells can become plasma cells to produce large quantities of antibodies. Memory cells are able to recognise the VZV antigens and destroy them in subsequent infections before the disease develops.

A teenager receiving B.C.G vaccination

A teenager is given the BCG vaccination in their upper arm. The BCG vaccine contains a live but weakened form of Mycobacterium bovis, the bacterium that causes tuberculosis (TB). (The vaccine is known as BCG because a strain of the bacterium known as Bacillus Calmette-Guerin is used). The vaccine is used to prevent tuberculosis, and works by triggering an immune response within the body to the bacteria, without causing the disease. The body having been exposed to the bacteria produces antibodies against it. The antibodies provide immunity by remaining in the body to provide protection against mycobacterium tuberculosis bacteria should it be encountered naturally. The immune response within the body is the same for each different bacteria or virus that the body experiences, the only difference being that the antibodies produced are specific to individual virus or bacteria.

Task 4 C

Explain how the antibodies produced in II will control the disease

Antibodies produced by having the BCG vaccination recognise the bacteria should it enter the body and attack it to remove the bacteria from the body. If TB bacteria enter the body there are three ways in which the antibodies can destroy the bacteria. The antibodies can attach themselves to the pathogen (bacteria) which neutralises the pathogen. The antibodies can also bind and cover the pathogen. This enables phagocytic cells, which are part of the body's immune system, to recognise and destroy the bacteria. The final way in which an antibody work is by binding to the pathogen and triggering a series of events to assist the phagocytic cells to identify the pathogen.

Task 5

2 recent mass immunization programmes evaluate the effects of the programmes, including effectiveness and uptake.

The Department of Health has released figures detailing the uptake of swine flu vaccine for England. 37% of people considered at risk from the disease (asthmatics, people with heart disease, pregnant women etc) were immunised. 20% of healthy children under 5 received the swine flu vaccine. 40% of front line healthcare workers have also been immunised.

It was also suggested by the Department of Health that anyone travelling to the Southern Hemisphere, should be vaccinated to prevent them from catching the virus and bringing it back.

In conclusion, looking at the figures released by the Department of Health regarding the swine flu vaccine uptake it suggests that much of the country was not that worried regarding the swine flu outbreak. So therefore the effectiveness of the swine flu mass immunization programme was not as successful as could have been hoped for. Only 37% those in the at risk group were immunised, so therefore 63% of the at risk group were either not offered or did not feel the need to take advantage of the swine flu immunization programme. 20% of healthy children under the age of 5 received the swine flu vaccine so an incredible 80% of healthy children under the age of 5 did not have the swine flu vaccine. 60% of front line healthcare workers did not take advantage of the swine flu vaccine. From these figures the mass swine flu immunization programme was not effective. The death toll from the swine flu virus now stands at 457 in the UK since the outbreak began almost a year ago. Probably several million Britons have had swine flu and most will have had either no symptoms or a mild illness.

In 1988, the World Health Assembly, adopted a resolution for the worldwide eradication of polio. This marked the launch of the Global Polio Eradication Initiative, which was spearheaded by the World Health Organization (WHO), Rotary International and UNICEF. Progress had been made during the 1980s towards elimination of the poliovirus in the Americas. Rotary International was committed to raise funds to protect all children from the disease.

Since the Global Polio Eradication Initiative was launched, the number of cases has fallen by over 99%. In 2008, only four countries in the world remained polio-endemic.

The WHO Region of the Americas (36 countries) was certified polio-free in 1994, this was followed in 2000 by the WHO Western Pacific Region (37 countries and areas including China) and the WHO European Region (51 countries) in June 2002.

In 2007 there were 164 supplementary immunisation activities. This lead to more than 400 million children being immunised in 27 countries. There are persistent pockets of polio transmission in northern India, northern Nigeria and the border between Afghanistan and Pakistan which remain key epidemiological challenges.

In conclusion this shows how effective mass immunization programmes can be in eradicating diseases.

Task 6

Have we entered the post antibiotic age as a result of previous overuse of antibiotics

Antibiotics have been used for approximately 50 years in the treatment of bacterial infections. They have been prescribed to cure diseases, eliminate infection and decrease healing time. In patients receiving antibiotics not all of the targeted bacteria died resulting in resistant strains of the bacteria. There are several causes of resistance to antibiotics these include the overuse or misuse of antibiotics. When antibiotics are repeatedly used in a person it has less effect on the bacteria it targets. Another cause is when the patient does not complete the course of antibiotics prescribed as their symptoms have been alleviated. Some bacteria can remain in the body and can become immune to a second dose of the antibiotic. Bacteria are also capable of developing resistance traits from free-floating DNA. When a resistant bacteria dies the DNA remains intact and can then enter a single bacterium where it may be incorporated into the next generation of that cell. Staphylococcus aureus is an example of bacteria resistant to antibiotics.

Resistant bacteria can be prevented from spreading through the improvement of infection control, isolation of hospital infections, developing new antibiotics and ensuring that prescribed medications are taken appropriately. In developing nations efforts are being made control infections through correct hand washing amongst healthcare workers and in identifying patients with drug resistant infections quickly and isolating them from others. For this to be effective it is necessary that doctors, patients and governments work together to provide education and research and that antibiotics are used correctly. If this is successful further development in the fight against resistance to antibiotics can occur.

In conclusion it appears that antibiotics remain successful in treating illnesses providing they are taken correctly by the patient to prevent them from developing resistance. A patient who does not take prescribed antibiotics correctly may find that in the future their symptoms cannot be alleviated.