1. 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
2. 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 analyzing
the symptoms (physical and mental signs).
3. Acute disease
Sudden and rapid onset
Symptoms disappear quickly
Symptoms lasting months or years
5. Physical disease
Results from permanent or temporary damage
to the body
It could be acute or chronic
Bronchitis Cold Sores Common
6. Infectious diseases
Organisms that invade the body
and cause disease inside are
Bacteria and Viruses are the best
know pathogens. They grow &
reproduce within the body of
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.
7. • Some examples to
• For a list of more
with details see pages
250-251 in your book
8. Influenza ('flu)
Influenza is a virus which causes a severe form of respiratory tract infection with generalized bodily
symptoms. It spreads around the world in epidemics and is responsible for much ill health as well as
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
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
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.
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 immunization) 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.
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
10. 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.
Zimbabwe's cholera epidemic hits 10,000
Zimbabwe's cholera epidemic hits 10,000
11. 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 diarrhea. 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.
12. • Clinical Tetanus sometimes known as “lock jaw”
-Spores deposited in tissue
- wound, burn, ulcer, compound fracture, operative wounds, drug
- tetanus neonatorum: infection of umbilical stump
- necrotic tissue (poor blood supply, anoxia)
- mixed infections, foreign bodies also contribute
-Toxins affect the central nervous system by causing continual
impulses to be sent to the muscles. They contract and become
-If not treated the person often dies a painful death as more and
more of the muscles are affected.
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.
14. 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
17. Droplet Infection
• Transmitted by pathogens
suspended in water
droplets that humans
cough or sneeze into the
• Airborne infections
generally affect the
respiratory tract, though
some of them affect other
parts of the body as well.
• The spread of these
diseases is curtailed by
19. Contamination Infection
• Pathogens enter
the body by way
food or water
often afflict the
• The intestinal
wastes of a person
who has this
disease are highly
20. Wound Infections
• Some pathogens
enter the body
• Even small cuts can
be serious if they
are not properly
• Enters through the
spreads to other 20
parts of the body.
21. Vector-carried Infection
• Insects or other arthropods
that carry pathogens to
other host organisms are
• Either mechanically, as
with food contamination
by pathogens carried on
the bodies of flies or
• By the bites of such
organisms as mosquitoes,
flies, or ticks, which inject
the pathogen into the
bloodstream of the host. 21
22. Immune Carriers
• Diseases are also spread by people, and
occasionally animals, who spread pathogens to
others without suffering from the disease
• They might have had the disease before and have
developed an immunity to it.