Human Health and Disease
What is health?
‘The state of complete physical, mental and social well-being’
To sustain a healthy lifestyle person needs:
•A balanced and varied diet
 Take exercise
 Proper shelter
 Enough sleep
Good hygiene will reduce the likelihood of infection
What is disease?
Disease is a disorder or malfunction of the mind
or body, which leads to a departure from good health.
Can be a disorder of a specific tissue or organ due to a
single cause. E.g. malaria.
May have many causes.
Often referred to as multifactorial. E.g. heart disease.
Disease diagnosed by a doctor analysing
the symptoms (physical and mental signs).
Acute disease
Sudden and rapid onset
Symptoms disappear quickly
E.g. influenza
Chronic disease
Long term
Symptoms lasting months or years
E.g. Tuberculosis
Categories of diseases
Physical disease
Results from permanent or temporary damage
to the body
Infectious diseases
Organisms that cause disease inside the human body are
called pathogens
Bacteria and Viruses are the best know pathogens.
Fungi, protists and parasites can also cause disease
Diseases are said to be infectious or communicable if
pathogens can be passed from one person to another.
Examples:
Influenza ('flu)
Influenza is a virus which causes a severe form of respiratory tract infection with generalised bodily symptoms. It spreads around the
world in epidemics and is responsible for much ill health as well as many deaths.
Symptoms
If you start to develop cold symptoms but starting more rapidly and rather more violently, with higher fever and severe aches and
pains, often in the back and muscles, then you may well be developing influenza. This may be associated with severe headache,
cough, and, as a result of the fever, intermittent sweating and shivering. Sometimes there is a gastrointestinal element, with vomiting
and/or diarrhoea.
Many people think they have had "flu" when all that they have suffered is a bad cold. When you have influenza you will know the
difference. Most people will find it impossible to leave their bed and feel terrible.
The worst symptoms usually last for three to five days, and then should begin to improve. It is common to need two to three weeks
off work as there is considerable debility left after the feverish illness is over. Do not be surprised to be quite depressed, this is a
natural after-effect of the condition.
Influenza makes everyone feel terrible, but most people recover. It does however have a small, but significant mortality, especially in
the very young, the very old, and those with poor immunity.
Causes
Influenza is caused by a virus which attacks our body cells resulting in various manifestations depending on the strain of the virus.
New mutations of the virus arise all the time and unfortunately immunity against one strain (which is conferred by exposure or
immunisation) does not protect against other strains. In the era of rapid air transport the world wide spread of a new type of influenza
can be extremely fast.
Measles
Chickenpox
Salmonella
Water or food borne
Salmonellosis is an infection with a bacteria called Salmonella. Most persons infected with Salmonella
develop diarrhea, fever, and abdominal cramps 12 to 72 hours after infection. The illness usually lasts 4
to 7 days, and most persons recover without treatment. However, in some persons the diarrhea may be so
severe that the patient needs to be hospitalized. In these patients, the Salmonella infection may spread
from the intestines to the blood stream, and then to other body sites and can cause death unless the
person is treated promptly with antibiotics. The elderly, infants, and those with impaired immune
systems are more likely to have a severe illness
Cholera
Cholera is an acute, diarrheal illness caused by infection of the intestine with the bacterium
Vibrio cholerae. The infection is often mild or without symptoms, but sometimes it can be
severe. Approximately one in 20 infected persons has severe disease characterized by
profuse watery diarrhea, vomiting, and leg cramps. In these persons, rapid loss of body
fluids leads to dehydration and shock. Without treatment, death can occur within hours.
Typhoid
Typhoid fever is contracted when people eat food or drink water that has been infected with
Salmonella typhi. It is recognized by the sudden onset of sustained fever, severe headache,
nausea and severe loss of appetite. It is sometimes accompanied by hoarse cough and
constipation or diarrhoea. Case-fatality rates of 10% can be reduced to less than 1% with
appropriate antibiotic therapy. Paratyphoid fever shows similar symptoms, but tends to be
milder and the case-fatality rate is much lower.
Sexually transmitted
Gonorrhoea
This is caused by bacteria and can affect the vagina, cervix, urethra, rectum or even the throat.
How could I get it?
Gonorrhoea can be passed on through:
· vaginal sex - where the man puts his penis in the woman's vagina
· anal sex - where the penis is put into the rectum
· oral sex - where partners lick or suck each others sexual parts.
Can I get it from toilet seats or towels?
You cannot it get it from toilet seats or swimming pools or by sharing cups and towels.
How do I know if I have it?
You may not know - that is the problem with gonorrhoea. And sometimes other sexually
transmissible infections can hide the symptoms of gonorrhoea.
Most women notice nothing at all until the infection has spread from the cervix. Some may notice:
· an unusual discharge
· pain or discomfort when passing water
· sore throat.
Men may notice:
· white or yellow discharge oozing from the tip of the penis. This is enough to stain the under pants.
· pain or discomfort urinating
· itching or discharge from the anus
· sore throat
There may be no symptoms in both men and women.
In women, it can not be picked up from cervical smear.
Syphilis
This is caused by the bacteria called Treponema pallidum which is spread
mainly by sexual intercourse, but can be passed on to your baby if are
pregnant. If you are pregnant, in this country you would have had this test
during your antenatal visit to the hospital. It usually starts as a painless
sore and may be any where in the private part, areas of contact during sex
as (the mouth, anus) or in women on the neck of the womb. If left
untreated it usually heals in 3 - 8 weeks. This is called primary syphilis.
About 8 to 10 weeks after the sore has healed, you feel unwell with flu-like
illness and develop skin rashes. Sometimes what looks like warts occur
around the genitals and the peri-anal areas. This could occur over period
sometimes lasting up to 2 years.. This period is known as secondary
syphilis. Again it may clear without any treatment. It then lurks in the body
and is only found when blood test are done for it and in others this may go
on to cause problems with the joints, heart and brain. This period is what
we call tertiary syphilis.

Clinical Tetanus
•Spores deposited in tissue
- wound, burn, ulcer, compound fracture, operative wounds, drug injection
- tetanus neonatorum: infection of umbilical stump
- necrotic tissue (poor blood supply, anoxia) needed
- mixed infections, foreign bodies also contribute
- 10 year latency reported
•Progression of disease
Malaria
Malaria infects an estimated 300 million people, and is spread by mosquitoes,
transfusions, and shared hypodermic needles. Control of mosquito populations has led
to declines in malaria in many areas. Infected individuals can be treayted with a variety
of medicines. However, some of the sporozoans that cause malaria heve developed
immunity to some of the more commonly employed medicines.
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Global Statistics
40% of the world's population is
at risk
300-500 million new cases/year
1.5-2.7 million deaths/year
Malaria is endemic to over 100
countries and territories
More than 90% of all cases are
in sub-Saharan Africa
Non-infectious diseases
Diseases that are not caused by pathogens
Mental diseases
A disease that affects a person’s mind
Thoughts, emotions, memory and personal and social behaviour
May have physical symptoms.
Example of a mild condition is claustrophobia
Serious mental diseases include:
Creutzfelt-Jacob disease (CJD)
Destroyed brain tissue resulting in spongy appearance
Infection with prion protein
Results in loss of co-ordination and mental derangement
Fatal
GENETIC CJD
Genetic CJD is a very rare illness. In this form, CJD is caused by an inherited abnormal gene. The illness is therefore not "caught"
in any way and there is no causal relationship between this form and BSE. In most cases, the illness is known within the family
because of the family history. Occasionally, genetic cases are seen in which no previous family history is identified. The definitive
test in relation to genetic CJD is a blood test in order that the gene can be analysed to see whether there is any genetic
abnormality. The United Kingdom has a population of around 58 million and there are only a few deaths due to genetic CJD in a
year.
IATROGENIC CJD
Iatrogenic CJD is also very rare. This is CJD which has been accidentally transmitted during the course of medical or surgical
procedures. The most important example of this in the United Kingdom relates to CJD transmitted via Human Growth Hormone
treatment in childhood. There are only a few deaths per year due to iatrogenic CJD in the United Kingdom. The diagnosis is usually
clear from the history of a relevant medical or surgical treatment in the past.
SPORADIC CJD
Sporadic CJD is numerically the most common form of CJD. It is not confined to the United Kingdom and, indeed, has been found in
every country in the world where it has been looked for. In general, it affects about one person per million of the population. There
are therefore some fifty to sixty deaths per year due to sporadic CJD in the United Kingdom. Similar figures are seen in other
countries such as Australia, Canada and the USA. The cause of sporadic CJD remains uncertain. However, the most favoured
current theory suggests that the normal prion protein in the brain undergoes a spontaneous change to the abnormal form, thereby
resulting in disease. If this theory is correct (and it has not been proven at this point) then the disease arises simply as a chance
event inside the brain. On this basis, it would not be "caught" in any way.
VARIANT CJD
Variant CJD was first reported in 1996. At this point in time, the CJD Surveillance Unit has not seen any cases of variant CJD with
symptoms that began before 1994. Aside from 6 cases in France, one case in Ireland, one case in Italy and one case in the USA,
variant CJD has been confined to the United Kingdom. The current view on variant CJD is that it has resulted from transmission of
infection from BSE in cattle to humans via infectivity in food.
Alzheimer’s disease
Degeneration of certain groups of brain cells
that usually secrete acetylcholine (neurotransmitter)
Symptoms:
-progressive degeneration of memory
-General decline in all mental faculties - dementia
Common in older people
Can occur in younger age groups - genetic
How common is it?
Schizophrenia affects one in every hundred people. This is about the same for many
different places and peoples across the world. It seems to be more common in city
areas.
Who does it affect?
Schizophrenia affects men and women equally. It rarely starts before the age of 15, but
can develop at any time after this. Men with schizophrenia usually notice the first signs
in their late teens or early twenties. Women are often first affected a little later, in their
twenties or thirties
We don’t yet know for sure what causes schizophrenia. It is likely to be a combination of
several different factors, which may be different for different people.
Genes
Brain Damage
New ways of producing pictures of the brain show that some people with schizophrenia
have larger spaces in the brain than people who don't suffer from the illness.
Stress
Street Drugs and Alcohol
Sometimes, the use of street drugs like ecstasy (e), LSD (acid),
amphetamines (speed), and cannabis (hash, marijuana, pot, ganja, skunk,
dope, spliffs, joints) seems to bring on schizophrenia.
In manic depressive illness, sufferers experience mood swings that are far beyond what
most people ever experience in the course of their lives. These mood swings may be
low, as in depression, or high, as in periods when we might feel very elated. These high
periods are known as ‘manic’ phases. Many sufferers have both high and low phases,
but some will only experience either depression or mania. A more technical term used to
describe this illness is ‘bipolar affective disorder’. This leaflet will describe both
aspects of the disorder, the particular problems they present, ways of coping with them
and the range of treatments available. It is a serious condition but, with the right
treatment, it is possible to live one’s life without too much interference.
Schizophrenia and manic depression
Usually occurs in young people
May not be apparent for some year owing to subtleties
And periods of perceptible good health
Clinical changes:
- changes in blood flow in brain
- imbalances in secretion of
neurotransmitters in brain.
Treatment – drugs to mimic or inhibit
neurotransmitters
Deficiency disease
Associated with malnutrition
Scurvy
In 1747 as the HMS Salisbury sailed from England to the Plymouth Colony, the ship's physician,
James Lind, performed a simple experiment to determine what might be effective as a cure for
scurvy. Scurvy was described as early as 1500 BC in the Ebers papyrus and other descriptions
appeared in Greek and Roman writings. It struck the crew of Magellan's around the world journey in
1519-22 and a British report in 1600 indicated that in the previous 20 years some 10,000 mariners
had been destroyed by the disease.
On May 20, 1747, Lind divided his 12 ill men into six groups of two each. All 12 shared a common
diet for breakfast, lunch and dinner but each group received a different supplement as follows:
1.quart of apple juice daily
2.25 drops of elixir vitriol (sulfuric acid and aromatics)
3.two spoonfuls of vinegar three times a day
4.concoction of herbs and spices
5.half-pint of sea water daily
6.two oranges and one lemon daily
The two men who ate the oranges and lemon recovered immediately. One was fit for duty in six
days and the other was also well in six days and was appointed as nurse to all the others. The two
men who drank apple cider improved but were not well enough to work. None of the others showed
any improvement.
Mr. Lind concluded that something in the citrus fruit was counteracting the cause of the scurvy disease so he
gave citrus fruits to all the other men and observed that all were cured of the disease.
night blindness
inability to see normally in subdued light. It is usually
a result of vitamin A deficiency. The rod cells, one of
two light-sensitive areas of the retina of the eye, are
impaired in their capacity to produce a chemical
compound called rhodopsin, or visual purple, that is
necessary for the perception of objects in dim light.
Consequently, the visual threshold, or the minimum
intensity of light necessary for sight, is greatly
increased. Folk medicine has long recognized the
role of the ingestion of liver in alleviating the
condition, but it was not until the first quarter of the
20th cent. that vitamin A was identified as the crucial
element. Treatment of night blindness consists of the
oral or intravenous administration of vitamin A.
Rickets
legs in a child with rickets
closeup of right knee
Examples of deficiency diseases
Scurvy – vitamin C
Night blindness – vitamin A
Rickets – vitamin D
Iron deficiency anaemia
Degenerative diseases
Usually associated with ageing
A gradual loss of function in one or several organs
or tissues can occur (associated with a progressive
destruction of specialised cells) in youth or middle age
Reasons for this loss of function:
- Immune system attack its own cells
- Deficiency in childhood which leads to
degeneration later in life.
Muscular Dystrophy
What is muscular dystrophy?
Muscular dystrophy (MD) is a broad term that describes a genetic (inherited) disorder of
the muscles. Muscular dystrophy causes the muscles in the body to become very weak.
The muscles break down and are replaced with fatty deposits over time.
Other health problems commonly associated with muscular dystrophy include the
following:
•heart problems
•scoliosis (a condition that causes the back bones to curve)
•obesity
The most common form of muscular dystrophy is called Duchenne’s muscular dystrophy
(DMD). Duchenne’s muscular dystrophy usually affects only males. It occurs in one out
of 3,500 live male births. Muscular dystrophy rarely affects girls, but when it does, the
condition is normally not as severe.
Types of degenerative diseases
Skeletal muscle and nervous system
Examples: muscular dystrophy, multiple sclerosis,
motor neurone and Alzheimer’s
Cardiovascular
Examples: coronary heart disease and stroke
Cancers
Social diseases
Hydrologists estimate that when the amount of fresh water per
person in a country drops below 1,700 cubic meters a year the
country is facing water stress.
Social factors
Factors affecting disease:
Standard of housing – overcrowding/unhygienic
Environmental factors such as levels of pollution and
Purity of water supply
Lack of food – deficiency diseases
Excess of food – diseases associated with obesity
And cardiovascular disease
Occupation
Exposure and/or abuse of drugs
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