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CHAPTER 1 PUBLIC HEALTH
INFECTIOUS DISEASE
1. An infectious disease is a clinically evident disease of
humans or animals
that damages or injures the host so as to impair host function,
and results
from the presence and activity of one or more pathogenic
microbial agents,
including viruses, bacteria, fungi, protozoa, multi-cellular
parasites, and
aberrant proteins
It is a disease caused by a microorganism that is potentially
transferable to
new individuals.
Example: HIV, Malaria
2. A communicable disease is an infectious disease that readily
spreads from
person to person, and is easily caught from an infected
person.
Example: a cold or chicken pox
3. A non communicable disease an infectious disease (i.e., with
a
microorganism etiology) that is not typically spread from person
to person.
The distinction, not spread from person to person, is important
since it
implies not only that:
i. individuals carrying the disease are not likely to spread
the
disease to others
ii. whatever led to the infection in such an individual likely
did not
include person to person contact
Example : Cancer, Asthma, Heart Disease
DISEASE CAUSED BY CONTAMINATION
1. Waterborne Disease
Waterborne diseases are caused by pathogenic microorganisms
which are directly transmitted when contaminated fresh water
is
consumed.
Waterborne disease can be caused by protozoa, viruses, or
bacteria,
many of which are intestinal parasites
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Water borne diseases spread by contamination of drinking
water
systems with the urine and feces of infected animal or
people.
This is likely to occur where public and private drinking water
systems
get their water from surface waters (rain, creeks, rivers,
lakes
etc.), which can be contaminated by infected animals or
people.
Runoff from landfills, septic fields, sewer pipes, residential
or industrial
developments can also sometimes contaminate surface water.
Example of Waterborne Disease
1. Diarrhea
is caused by a bacterial, viral, or parasitic infection.
Diarrhea may be accompanied by cramping, abdominal pain, nausea,
an
urgent need to use the bathroom, or loss of bowel control. Some
infections
that cause diarrhea can also cause a fever and chills or bloody
stools.
2. Cholera
Cholera occurs because of the bacteria present in water
contaminated
by incorrect sanitation, or in improperly cooked fish,
especially
shellfish
Cholera is transmitted through feces contaminated with the
bacterium.
The contamination normally appears when sewage water is
released
into the waterways, affecting the drinking water, fish and food
washed
in the water. In normal conditions it doesn't spread from person
to
person, but this is possible in poor sanitary conditions.
Common symptoms include severe diarrhea abdominal cramps,
fever
and vomiting.
If not treated immediately, the dehydration can cause death
through
circulatory volume shock in just a few hours.
Cholera can be prevented by respecting a number of sanitary
rules
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3. Typhoid Fever
is caused by the infection with a bacterium called Salmonella
typhi. It
is very common, as it is transmitted by water or food
contaminated
with feces from infected people.
symptoms including a high fever, slowly rising from 39 to 40
degrees
Celsius (103 to 104 degrees Fahrenheit), chills, bradycardia
(low pulse
rate) and weakness
Typhoid fever can be dangerous, and if untreated, it has a
mortality
rate between 10 and 30%.
A vaccine is available and it is highly recommended for
anyone
traveling to regions where typhoid fever is common.
4. Dysentery
Dysentery is characterized by a severe inflammation of the
intestines,
affecting the body in a significant measure. Dysentery used to
be a
common disease in the past centuries, but it is becoming less
common
today.
Pathogen agent : Shigellosis, caused by Shigella bacteria,
an
amoeba called Entamoeba histolytica that transmitted by
contaminated water
The usual sign of epidemic dysentery is blood appearing in the
feces,
associated with diarrhea, abdominal cramps, fever and rectal
pain.
Sepsis and kidney failure may occur in more severe cases.
Prevention
Clean water is a pre-requisite for reducing the spread of
water-borne
diseases
It is well recognized that the prevalence of water-borne
diseases can
be greatly reduced by provision of clean drinking water and
safe
disposal of feces
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Water is disinfected to kill any pathogens that may be present
in the
water supply and to prevent them from growing again in the
distribution systems
Disinfection is then used to prevent the growth of
pathogenic
organisms and to protect public health and the choice of the
disinfect
depends upon the individual water quality and water supply
system.
Without disinfection, the risk from waterborne disease is
increased.
The two most common methods to kill microorganisms in the
water
supply are: oxidation with chemicals such as chlorine, chlorine
dioxide
or ozone, and irradiation with Ultra-Violet (UV) radiation
2. Food borne Disease
is any illness resulting from the consumption of contaminated
food,
pathogenic bacteria, viruses, or parasites that contaminate
food,
rather than chemical or natural toxins.
Cause by improper handling, preparation, or food storage.
More than 250 different food borne diseases have been
described.
Most of these diseases are infections, caused by a variety of
bacteria,
viruses, and parasites that can be food borne
Common food borne disease
1. Campylobacter
is a bacterial pathogen that causes fever, diarrhea, and
abdominal
cramps.
It is the most commonly identified bacterial cause of diarrheal
illness
in the world.
These bacteria live in the intestines of healthy birds, and most
raw
poultry meat has Campylobacter on it.
Eating undercooked chicken or other food that has been
contaminated
with juices dripping from raw chicken is the most frequent
source of
this infection.
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2. Salmonella
is also a bacterium that is widespread in the intestines of
birds,
reptiles and mammals.
It can spread to humans via a variety of different foods of
animal
origin.
The illness it causes, salmonellosis, typically includes fever,
diarrhea
and abdominal cramps.
In persons with poor underlying health or weakened immune
systems,
it can invade the bloodstream and cause life-threatening
infections.
3. E. coli
is a bacterial pathogen that has a reservoir in cattle and other
similar
animals.
Human illness typically follows consumption of food or water
that has
been contaminated with microscopic amounts of cow feces.
The illness it causes is often a severe and bloody diarrhea and
painful
abdominal cramps, without much fever.
In 3% to 5% of cases, a complication called hemolytic uremic
syndrome (HUS) can occur several weeks after the initial
symptoms.
This severe complication includes temporary anemia, profuse
bleeding,
and kidney failure.
Prevention
1. Keep clean
Wash your hands before handling food and often during food
preparation
Wash your hands after going to the toilet
Wash and sanitize all surfaces and equipment used for food
preparation
Protect kitchen areas and food from insects, pests and other
animals
2. Separate raw and cooked
Separate raw meat, poultry and seafood from other foods
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Use separate equipment and utensils such as knives and cutting
boards for
handling raw foods
Store food in containers to avoid contact between raw and
prepared foods
3. Cook thoroughly
Cook food thoroughly, especially meat, poultry, eggs and
seafood
Bring foods like soups and stews to boiling to make sure that
they have
reached 70C. For meat and poultry, make sure thatjuices are
clear, not
pink. Ideally, use a thermometer
Reheat cooked food thoroughly
4. Keep food at safe temperatures
Do not leave cooked food at room temperature for more than 2
hours
Refrigerate promptly all cooked and perishable food (preferably
below 5C)
Keep cooked food piping hot (more than 60C) prior to serving
Do not store food too long even in the refrigerator
Do not thaw frozen food at room temperature
5. Use safe water and raw materials
Use safe water or treat it to make it safe
Select fresh and wholesome foods
Choose foods processed for safety, such as pasteurized milk
Wash fruits and vegetables, especially if eaten raw
Do not use food beyond its expiry date
3. Vector Disease
Occur in infectious microbes such as viruses, bacteria,
parasite, etc
that present in a vector.
Mosquito, birds, rat, insects and all others pests that transfer
diseases are
referred to as a vector.
The vector picks up the disease organism from an infected host,
an
animal or a human, and transmits it either to an intermediary
host or
directly to the human host.
The transfer happens directly by bites, or infestation of
tissues, or
indirectly through disease transmission.
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Example of Vector Disease
No Vector Disease
1. Aedes Mosquito Chikungunya
Dengue Virus
West Nile Virus
Yellow Fever
2. Anopheles Mosquito Malaria
3. Bird Avian influenza (Bird flu)
4. Rats Leptospirosis
Plague (via Fleas)
Leishmaniasis (via Sand Fly)
Symptom of disease
1.Dengue
Dengue is transmitted by the bite of an Aedes mosquito infected
with any
one of the four dengue viruses. It occurs in tropical and
sub-tropical areas of
the world. Symptoms appear 314 days after the infective
bite.
Dengue fever is a febrile illness that affects infants, young
children and
adults.
Symptoms range from a mild fever, to incapacitating high fever,
with severe
headache, pain behind the eyes, muscle and joint pain, and rash.
There are
no specific antiviral medicines for dengue. It is important to
maintain
hydration. Use of acetylsalicylic acid (e.g. aspirin) and non
steroidal anti-
inflammatory drugs (e.g. Ibuprofen) is not recommended.
Dengue haemorrhagic fever (fever, abdominal pain, vomiting,
bleeding) is a
potentially lethal complication, affecting mainly children.
Early clinical
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diagnosis and careful clinical management by experienced
physicians and
nurses increase survival of patients
In January 2009, reported there are 5000 cases of dengue.
2. Malaria
Malaria is a major disease in the tropics and subtropics. Each
year, it is
estimated that more than 225 million cases of malaria, killing
around 781
000 people according to WHO. Historical records suggest that the
disease has
infected human since the beginning of mankind.
When a person is infected, he or she will suffer symptoms
including fever,
chills, headache, muscle pain, sweating or vomiting. Severe
cases will
progress to coma and death. These symptoms normally appear
between 10
to 15 days after being bitten by the Anopheles mosquito. The
disease can
also be transmitted from a mother to her unborn baby and by
blood
transfusions.
3. Bird Flu
Bird flu or avian influenza is a highly contagious disease which
can cause
sickness and death especially in domesticated birds like
chickens, geese,
ducks and turkeys.
Bird flu is caused by avian influenza (AI) virus which normally
only infects
birds, less commonly pigs and rarely horses, seals, whales,
humans and
other animals. There are many subtypes of AI virus.
The subtype H5N1 currently circulating among birds worldwide was
first
detected in 1997. Since 2003 has spread among many countries in
Asia and
Europe causing heavy mortalities in poultry flocks and wild
birds. Over 200
million poultry and birds have died or were killed since 1997
due to this
virus. The H5N1 virus is also capable of causing disease in
humans under
certain circumstances.
Malaysia has been free from bird flu until August 2004 when
cases were
detected for the first time, in Kelantan. The disease was
promptly eradicated
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and Malaysias disease-free status was reinstated on 5 January
2005.
Isolated cases are again reported exactly one year later, in
Kuala Lumpur
which is being eradicated.
This disease can spread by migration birds and movement of
infected bird
Birds get infected when they come into contact with these, with
dead birds
and with contaminated feed and water, equipments, vehicles and
other
objects. Virus is shed in feces, saliva and nasal secretions of
infected birds.
Avian influenza viruses do not usually infect humans but people
can contract
the disease through close contact with infected poultry and the
feces. Only
140 human cases reported, mostly in South East Asia (Vietnam,
Thailand,
Indonesia, Cambodia and China) with over 70 deaths, despite
widespread
outbreaks in poultry and wild birds.
4. Leptospirosis
Leptospirosis is a most common zoonotic disease caused by
Leptospira
Interrogans bacterium, which affects both humans and animals. It
is
transmitted through contaminated fresh water, food or soil which
is
swallowed or comes in contact with broken skin, eyes and
mucous
membranes.
This Leptospira spreads through infected animals urine and
contagious while
it is moist.
Rats, mice and voles known to be primary hosts while dogs, deer,
rabbits,
cows, sheeps, and certain marine mammals are possible carrier
and known
to be secondary hosts.
This biphasic disease normally begins with flu-like symptoms
such as fever,
chills and intense headache. It will then cause meningitis,
renal failure and
liver damage that cause jaundice.
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Disease Transmission
NON COMMUNICABLE DISEASE
1. Lead
Lead accounts for most of the cases of pediatric heavy metal
poisoning
(Roberts 1999).
It is a very soft metal and was used in pipes, drains, and
soldering materials
for many years.
Millions of homes built before 1940 still contain lead (e.g., in
painted
surfaces), leading to chronic exposure from weathering, flaking,
chalking,
and dust.
Every year, industry produces about 2.5 million tons of lead
throughout the
world.
Most of this lead is used for batteries. The remainder is used
for cable
coverings, plumbing, ammunition, and fuel additives. Other uses
are as paint
pigments and in PVC plastics, x-ray shielding, crystal glass
production, and
pesticides.
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Since lead is chemically very similar to calcium, it is handled
by the body as
if it were calcium. Thus the first place to which it is
transported is to the
plasma and the membrane sites in soft tissues. It is then
distributed to the
other sites where calcium plays an important role, most notably
in the teeth
of developing children and in bone at all ages.
Target organs are the bones, brain, blood, kidneys, and thyroid
gland
2. Mercury
Mercury is generated naturally in the environment from the
degassing of the
earth's crust, from volcanic emissions.
It exists in three forms: elemental mercury and organic and
inorganic
mercury.
Mining operations, chloralkali plants, and paper industries are
significant
producers of mercury (Goyer 1996).
Atmospheric mercury is dispersed across the globe by winds and
returns to
the earth in rainfall, accumulating in aquatic food chains and
fish in lakes
(Clarkson 1990).
Mercury compounds were added to paint as a fungicide until 1990.
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These compounds are now banned; however, old paint supplies and
surfaces
painted with these old supplies still exist.
Mercury continues to be used in thermometers, thermostats, and
dental
amalgam. (Many researchers suspect dental amalgam as being a
possible
source of mercury toxicity [Omura et al. 1996; O'Brien
2001].)
Medicines, such as mercurochrome and merthiolate, are still
available.
Algaecides and childhood vaccines are also potential
sources.
Inhalation is the most frequent cause of exposure to mercury.
The organic
form is readily absorbed in the gastrointestinal tract
(90-100%); lesser but
still significant amounts of inorganic mercury are absorbed in
the
gastrointestinal tract (7-15%).
Target organs are the brain and kidneys.
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3. Insecticide
Pesticides are designed to kill "pests", but some pesticides can
also cause
health effects in people. The likelihood of developing health
effects depends
on the type of pesticide and other chemicals that are in the
product you are
using, as well as the amount you are exposed to and how long or
often you
are exposed.
Most often, pesticides affect the nervous system (system in your
body that
controls your nerves and muscles).
Some health effects from pesticide exposure may occur right
away, as you
are being exposed. Some symptoms may occur several hours after
exposure.
Other effects may not be noticed for years, for example
cancer.
Pesticides can enter your body during mixing, applying, or
clean-up
operations. There are generally three ways a chemical or
material can enter
the body:
o through the skin (dermal),
o through the lungs (inhalation), or
o by mouth (ingestion).
In general, the risk of illness increases as the concentration
(strength) of the
pesticide, and duration (length) of exposure increases. "How
much" and "how
long" is necessary to cause illness will depend on the exact
type of pesticide
4. Asbestos
Asbestos is the name given to a group of naturally occurring
minerals used in
certain products, such as building materials and vehicle brakes,
to resist heat
and corrosion. Asbestos includes chrysotile, amosite,
crocidolite, tremolite
asbestos, anthophyllite asbestos, actinolite asbestos, and any
of these
materials that have been chemically treated and/or altered.
The inhalation of asbestos fibers by workers can cause serious
diseases of
the lungs and other organs that may not appear until years after
the
exposure has occurred.
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For instance, asbestosis can cause a buildup of scar-like tissue
in the lungs
and result in loss of lung function that often progresses to
disability and
death.
Asbestos fibers associated with these health risks are too small
to be seen
with the naked eye, and smokers are at higher risk of developing
some
asbestos-related diseases
Employee exposure to asbestos must not exceed 0.1 fiber per
cubic
centimeter (f/cc) of air, averaged over an 8-hour work shift.
Short-term
exposure must also be limited to not more than 1 f/cc, averaged
over
30 minutes. Rotation of employees to achieve compliance with
either
permissible exposure limit (PEL) is prohibited.
5. Cadmium
Cadmium is a byproduct of the mining and smelting of lead and
zinc
It is used in nickel-cadmium batteries, PVC plastics, and paint
pigments.
It can be found in soils because insecticides, fungicides,
sludge, and
commercial fertilizers that use cadmium are used in
agriculture.
Cadmium may be found in reservoirs containing shellfish.
Cigarettes also contain cadmium. Lesser-known sources of
exposure are
dental alloys, electroplating, motor oil, and exhaust.
Inhalation accounts for 15-50% of absorption through the
respiratory
system; 2-7% of ingested cadmium is absorbed in the
gastrointestinal
system. Target organs are the liver, placenta, kidneys, lungs,
brain, and
bones.
6. Nitrate
Nitrates and nitrites are chemicals that can be found naturally
in our
environment. Two of earths most common elements, nitrogen and
oxygen,
combine to form these nitrogen-containing compounds. Nitrates
are essential
(needed) nutrients for plants to grow. Nitrates can be found in
the air, soils,
surface waters and ground water
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The main exposure route to nitrates is by eating vegetables and
preserved
meats (70%). The remainder of the nitrate in a typical diet
comes from
drinking nitrate-contaminated water (about 21%)
Exposure to nitrates and nitrites are not usually an immediate
(acute) health
threat. When you eat or drink nitrates, they are absorbed from
the small
intestine (gut) into the blood. Nitrates then enter the large
intestine from the
blood.
If certain, normal conditions exist in the intestine, such as a
low pH, the
nitrate is simply processed and removed as waste without any
harmful
effects.
However, under other conditions, such as a high pH in the
intestine, the
nitrate will be changed into nitrite. This nitrite is then
reabsorbed into the
blood where it will react with the bloods hemoglobin iron to
form
methemoglobin.
The hemoglobin in our blood carries (transports) oxygen
throughout our
body.
The condition where the nitrite reacts with the iron and
hemoglobin is known
as methemoglobinemia (often called blue baby syndrome).
Unlike hemoglobin that carries oxygen throughout our body,
methemoglobin
is unable to transport oxygen.
A person who has methemoglobinemia can lack the proper oxygen
levels
needed for the body to function correctly. One of the signs
of
methemoglobinemia is cyanosis (turning a blue color).
7. Particular Matter
Particular matter is the sum of all solid and liquid particles
suspended in air,
many of which are hazardous. This complex mixture contains for
instance
dust, pollen, soot, smoke, and liquid droplets
Particles are either directly emitted into the air by sources
such as
combustion processes and windblown dust, or formed in the
atmosphere by
transformation of emitted gases such as SO2.
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In long-term exposure to current ambient particulate matter
concentrations
may affect the lungs of both children and adults and may reduce
life
expectancy by a few months, mainly in subjects with pre-existing
heart and
lung diseases.
Fine particles are more dangerous than coarse particles. Apart
from the size
of the particles, other specific physical, chemical, and
biological
characteristics that can influence harmful health effects
include the presence
of metals, PAHs, other organic components, or certain
toxins.
When particulate matter is combined with other air pollutants,
the individual
effects of each pollutant are cumulated. In certain cases,
especially for
combinations of particulate matter with ozone or allergens,
effects were
shown to be even greater than the sum of the individual
effects.
Certain groups of people are more susceptible to suffer health
effects due to
ambient particulate matter. These include elderly people,
children, people
with a pre-existing heart and lung disease, asthmatics, and
socially
disadvantaged and poorly educated populations.
8. Dioxin
Dioxins are a group of chemically-related compounds that are
persistent
environmental pollutants.
Dioxins are found throughout the world in the environment and
they
accumulate in the food chain, mainly in the fatty tissue of
animals.
More than 90% of human exposure is through food, mainly meat and
dairy
products, fish and shellfish. Many national authorities have
programmes in
place to monitor the food supply.
Dioxins are highly toxic and can cause reproductive and
developmental
problems, damage the immune system, interfere with hormones and
also
cause cancer.
Short-term exposure of humans to high levels of dioxins may
result in skin
lesions, such as chloracne and patchy darkening of the skin, and
altered liver
function.
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Long-term exposure is linked to impairment of the immune system,
the
developing nervous system, the endocrine system and
reproductive
functions. Chronic exposure of animals to dioxins has resulted
in several
types of cancer.
No Type of Heavy Metal Source/Exposure Organ Target/
Disease
1. Lead Used in pipes, drains, and
soldering materials for
many years.
Exposure from
weathering, flaking,
chalking, and dust.
Used for batteries.
The remainder is used for
cable coverings,
plumbing, ammunition,
and fuel additives.
Other uses are as paint
pigments and in PVC
plastics, x-ray shielding,
crystal glass production,
and pesticides.
Transport to
soft tissues
Target organs
are the bones,
brain, blood,
kidneys, and
thyroid gland
2. Mercury generated naturally in the
environment from the
degassing of the earth's
crust, from volcanic
emissions
Mining operations,
chloralkali plants, and
Target organ:
brain and
kidney.
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paper industries are
significant producers of
mercury
Used in paint,
thermometer medicine
and medical equipment
Expose by inhalation
3. Insecticide From pesticide
enter body during mixing,
applying, or clean-up
agriculture operations
affect the
nervous system
4. Asbestos used in certain products,
such as building materials
and vehicle brake
cause serious
diseases of the
lungs and other
organs
5. Cadmium byproduct of the mining
and smelting of lead and
zinc
used in nickel-cadmium
batteries, PVC plastics,
and paint pigments.
can be found in soils
because insecticides,
fungicides, sludge, and
commercial fertilizers that
use cadmium are used in
agriculture.
Cadmium may be found in
reservoirs containing
shellfish
Cigarette
Effect liver,
placenta,
kidneys, lungs,
brain, and
bones.
Absorb in
respiratory
system and
gastrointestinal
system
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6. Nitrate is by eating vegetables
and preserved meats
from drinking nitrate-
contaminated water
baby blue
syndrome
lack of oxygen
7. Particular Matter From dust, pollen, soot,
smoke, and liquid droplets
emitted into the air by
sources such as
combustion processes
heart and lung
disease
High risk to
elderly people,
children, people
with a pre-
existing heart
and lung
disease,
asthmatics, and
socially
disadvantage
8. Dioxin a group of chemically-
related compounds that
are persistent
environmental pollutants.
exposure is through food,
mainly meat and dairy
products, fish and
shellfish.
cause
reproductive
and
developmental
problems,
damage the
immune system,
interfere with
hormones
also cause
cancer.