CPHM112
M IDT ERM S
1st Year
2nd Semester
COMMUNITY AND PUBLIC HEALTH
FOR MEDICAL LABORATORY SCIENCE
COMMUNICABLE DISEASE
 Communicable Disease: transmitted from one host to another
 Contagious Disease: easily transmitted
COMMUNICABLE DISEASE
 Communicable diseases are readily transferred from one
infected person to a susceptible and uninfected person and
maybe caused by microorganisms.
 Acute Disease
 disease that occurs abruptly / suddenly develops
 developing in a short period of time
 Chronic Disease
 disease that is present in a person for a long period of time,
example is elephantiasis
 maybe life threatening
 prone in causing permanent disability to a person
Example: COVID-19
• Elephantiasis
 parasitic infection where hands and feet of a person enlarged
 enlargement is due to the blockage of parasites in the
lymphatic system of the person will take years usually a
minimum of 3 years
 when the parasites die, they will calcify
 Latent Disease
 remains inactive on the body, but when the time comes that
the person’s immune system becomes slow or
immunocompromised, that inactive disease may develop
 example is a tuberculosis, chicken pox, HIV, AIDS
 reactivation of chicken pox is known as shingles
 Secondary Infections – infections that develops after having
a prior infection
Example: Amebiasis: a parasite that causes diarrhea
 The ulceration caused by the amoeba in your large intestine may
be a source of secondary bacterial infection.
 Bacteremia – presence of bacteria in the blood
 Septicemia – presence and multiplication of bacteria in the
blood ; poisoning of the blood caused by multiplied bacteria ;
may be called sepsis
• If the person has septicemia, the person usually will have
multiple organ failure because of extensive inflammation
inside the body
• Usual cause of death to the patients who have extensive
bacterial infection
• The normal response of our immune system is to develop
inflammation
• Events of Inflammation: increase in blood flow and
increase in the permeability among the pores of our blood
vessels
• Hypovolemia: decrease in blood volume
 Toxemia – bacteria that produces and releases toxins
Example: Tetanus
 Viremia – presence of viruses in the blood.
Epidemic
Pandemic
Incidence
Prevalence
Signs
Symptoms
Pathology
Etiology
Pathogenesis
Infection
Disease
Pathogen
Infection
Virulence
Pathogenicity
Invasiveness
Infectivity
Toxigenicity
Septicemia
outbreaks; sudden increase in the
number of cases in disease
worldwide outbreaks; disease of
worldwide distribution
number of infected people during a
particular time period (i.e. year);
developing disease
number of diseased people at any given
time; existing cases of disease
measurable changes; objective
patient complaint; subjective
study of disease
cause of disease
disease process
colonization by microbe
illness
organism with potential to cause disease
pathogen is growing in or on host
degree or intensity of pathogenicity
ability of the microorganism to cause
infection; pathogenicity of the given
microorganism will depend on the
structure
ability of pathogen to spread to other
tissues in body
ability of pathogen to establish infection
ability of pathogen to secrete toxins
infection in which pathogen grows
massively in the body, being found in
blood and throughout organs. Usually
leads to death.
KOCH’S POSTULATES
Developed in late 1800’s by Robert Koch, provide basic logical
proof that disease is caused by a microbe / communicable
1. Microbe must be present in every case of disease, but
absent from healthy individuals.
2. Suspected microbe must be isolated from diseased host and
grown in culture.
3. Same disease must result when isolated microbe is
introduced into healthy host.
4. Same microbe must be isolated again from second diseased
host
DISEASE ETIOLOGY: KOCH’S POSTULATES
TERMINOLOGIES
Sporadic
Endemic
occasional cases
constantly present; ex. malaria
FANTILANAN, R.F / SY 22-23
NORMAL MICROBIOTA/FLORA
CHAIN OF INFECTION
 Compete for living space and nutrients with pathogens
 Microorganism that are good bacteria, they prevent harmful
bacteria in establishing infection
 Example: Lactobacillus Acidophilus – provides acidic pH in
the vagina; prevents pathogenic organisms to establish infection
 Normal pH of vagina: 5
Table 13.1
Sites That Harbor a Normal Flora
 Skin and its contiguous mucous membranes
 Upper respiratory tract
 Gastrointestinal tract (various parts)
 Outer opening of urethra
 External genitalia
 Vagina
 External ear canal
 External eyelids (lids, conjunctiva)
Table 13.2
Sterile (Microbe-Free) Anatomical Sites and
Fluids
All Internal Tissues and Organs
 Heart and Circulatory System
 Liver
 Kidneys and Bladder
 Lungs
 Brain and Spinal Cord
 Muscles
 Bones
 Ovaries/testes
 Glands (pancreas, salivary, thyroid)
 Sinuses
 Middle and Inner ear
 Internal eye
Fluids within an Organ or Tissue
 Blood
 Urine in kidneys, ureters, bladder
 Cerebrospinal fluid
 Saliva prior to entering the oral cavity
 Semen prior to entering the urethra
 Amniotic fluid surrounding the embryo and fetus
1. Etiologic Agent
 The extent to which any microorganisms is capable of
producing an infectious process depends on the number of
microorganisms (pathogenicity), the ability of the
microorganisms to enter the body, the susceptibility of the
host, and the ability of microorganism to live in the host’s
body.
2. Reservoir
 There are many reservoirs, or sources of microorganisms.
Common sources are the other humans, the client’s own
microorganisms, plants, animals, or the general
environment. People are the most common source of
infection for others and for themselves.
Spread of Disease:
Reservoir: source of organisms
 Humans
 Animals (zoonoses)
 Environment
3. Portal of Exit from the Reservoir
 Before an infection can establish itself in a host, the
microorganism must leave the reservoir.
Portals of Exit
OPPORTUNISTIC PATHOGENS

Organisms that cause disease when they enter different
environment
– Staphylococcus aureus enters break in skin
– Escherichia coli enters peritoneal cavity from burst appendix
• Peritonitis – infection of peritoneal cavity
– Clostridium difficile colonizes intestines when normal flora
have been killed by antibiotics
Types of microorganism causing infections:
 Bacteria
–
the
most
common
infection-causing
microorganisms/communicable diseases
 Viruses – consist primarily of nucleic acid and therefore must
enter living cells in order to produce infection.
 Fungi – includes yeast and mold.
 Parasites – live on other living microorganism
FANTILANAN, R.F / SY 22-23
4. Mode of Transmission
 Direct Transmission: involves immediate and direct
transfer of microorganisms from person to person through
touching, biting, kissing, or sexual intercourse.
• Droplet spread is also a form of direct transmission but
can occur only if the source and the host are within 3
feet of each other. Sneezing, coughing, spitting, singing,
or talking can project droplet spray into the conjunctiva
or onto the mucous membranes of the eyes, nose, or
mouth of another person.
 Indirect transmission: indirect transmission may either
vehicle- borne or vector borne.
 Vehicle: any substance that serves as an intermediate
means to transport and introducing infectious agent into
susceptible host through a suitable portal of entry;
inanimate object
• Fomites: inanimate objects that may be harboring
bacteria or microbes
 Vector: is an animal or flying or crawling insects that serves
as an intermediate means of transporting the infectious
agents; animate object
Spread of Disease:
 Contact (direct ; indirect (fomite) )
 Droplet
 Vehicle
 Vector
SURVIVING HOST DEFENSES
5. Portal of Entry to the Susceptible Host
 Before a person can became infected, microorganisms
must enter the body. The skin is a barrier to infectious
agents; however, any break in the skin can readily serve as
portal of entry. Often, microorganisms enter the body of the
host by the same route they used to leave the source
Portals of Entry:
- Skin
- Gastrointestinal Tract
- Respiratory
- Urogenital
- Via Placenta
- Parenteral (injection, bite)
ADDITIONAL VIRULENCE FACTORS
6. Susceptible Host
 A susceptible host is any person who is at risk for
infection.
 A compromised host is a person “at increased risk”, an
individual who for one or more reasons is more likely than
others to acquire an infection. Impairment of the body’s
natural defenses and a number of other factors can affect
susceptibility to infection.
ATTACHMENT
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Fimbriae
Glycocalyx
Hooks
Suction Discs
Viral Spike
FANTILANAN, R.F / SY 22-23
Disease cycle maybe broken down by these factors:
 Increasing host resistance
 Destruction of the source and the reservoir
 Destruction of the agent in the environment
 Avoidance of exposure
Controlling Infectious Diseases
 Treatment – prophylaxis such as antibiotics, antiviral drugs.
 Prevention – hygiene, disinfectants, sterilization, antiseptics
and vaccination.
Antiseptics and Disinfectants
 Chemical substances that destroy microorganisms.
 Antiseptic can be applied safely to the body. E.g. on skin,
ethanol and isopropanol.
 Disinfectants cannot be used on the body directly but are
used to clear work surfaces, crockery, cutlery, instruments
etc. e.g. hypochlorites in commercial disinfectants, phenol,
aldehydes, chlorxylenol (dettol) and iodine in more dilute
form can be used as antiseptics.
Sterilisation
 Removal of any living organisms from a non-living object or
material. E.g. water, operating theatre gowns.
 Heat – pasteurizing milk, tinned food.
 Steam – autoclave where steam under pressure is fed into a
sealed chamber.
 Radiation – longer wave lengths have no effect shorter
wavelength such as UV light results in death.
3. MMR ( Measles, Mumps, Rubella ) Vaccine
• Measles – caused by Measles virus
• Mumps – caused by Mumps virus
• German measles – caused by Rubella virus
4. Hib (H. influenza type B) Polysaccharide Vaccine
• Meningitis – caused by Haemophilus influenza
5. Hepatitis B Vaccine, an early start of hepatitis B reduces the
chance of being protects and becoming cancer.
6. BCG (Bacillus of Calmette and Guerin)
• BCG given at the earliest possible protects against the
possibility of infection from other family members.
• Tuberculosis – caused by Mycobacterium tuberculosis
7. CDT (Cholera, Dysentery, Typhoid)
• Cholera – caused by Vibrio cholera
• Dysentery – caused by Shigella dysenteriae
• Typhoid – caused by Salmonella typhi
SPECIFIC PROTECTION AGAINST DEFENSE
I.
Immunization
 Is the process of introducing vaccine into the body to
produce antibodies that will protect our body against a
specific infectious agent.
 Giving antigens from a disease causing organism, either by
injection or orally.
 In order for the immune system to learn to make antibodies
against the organism.
 So that the body will be able to respond fast enough to
prevent the organism from causing an infection.
 Artificial active immunity
Immunization against communicable disease
 For infants
 Following exposure
 For all persons in endemic areas
 For person subject to unusual risk
 For known cases
II. Chemoprophylaxis
 Administration of drugs to prevent occurrence of infection.
 E.g. Penicillin for gonorrhea, chloroquine for malaria, INH
for tuberculosis
III. Mechanical Prophylaxis
 Placing mechanical barriers between the sources of agent
and host such as use of mosquito nets, masks or gloves
VACCINE AVAILABLE FOR ROUTINE IMMUNIZATION
1. DPT (Diphtheria, Pertusis and Tetanus) Vaccine.
• An early start with DPT reduces the chance of severe
pertussis.
• Diphtheria – caused by Corynebacterum diphteriae
• Pertussis - caused by Bordetella pertussis
• Tetanus – caused by Clostrodium tetani
2. OPV (Oral Polio Vaccine) the extent of protection against
polio is increased the earlier the OPV is given.
• Poliomyelitis – caused by Polio virus
FANTILANAN, R.F / SY 22-23