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Epidemiology
Epidemiology: it is the science that deals with studying the occurrence
and distribution of health and disease in human population
Epi= upon
Dem= people
Ology= science or knowledge
* Epidemiology is categorized into: demography (people population)
statistical epidemiology and preventive epidemiology.
* Preventive epidemiology deals with the studying factors which
determine disease occurrence. For a disease to occur three factors must be
present and interact with each other. These factors may be:
1. Intrinsic (internal) e.g. agent (A), host (H).
2. Extrinsic (external) e.g. environment.
Agent (A):
Agents the true case of the disease without it which a specific disease
cannot occur
* Examples of the agents are:
1. Microorganism as bacteria, viruses
2. Chemical substance (agent):*poisons as exposure to Co.
* Allergens as medical products.
3. Physical agents as radiation, excessive cold or heat.
4. Exposure for carcinogenic substances as the case when eating outdated
food or frying food frequently boiled oil.
5. Nutritional disturbances as when a child is eating too much
carbohydrate and lees protein will develop kwashiorkor. Or in eating
cholesterol rich diet ---------- cholesterolemia
Vitamin deficiency decrease ------ ricket
* Agents has certain properties that determine the mechanism of
disease transmission, its morbidity (ability to cause disease or
mortality (ability to cause death)
* Factors determine the effect of an agent: properties
1. Resistance: its ability to survive in a free state to resist
temperature, light, other influences.
2. Viability: it is ability to multiply outside human body e.g.
bacteria can multiply in non living media such as food and milk.
But viruses can multiply within living cells.
3. Invasiveness, virulence and pathogenicity: its ability to cause the
disease, some viruses is very virulent (strong) e.g. poliomyelitis,
other are not (weak) e.g. common cold viruses.
4. Effective dose, duration.
5. Host specificity
Host (H):
This is the person susceptible to illness. Host may be human or non
human
* factors which affect and Control the host
1. Age (some disease are age – related as poliomyelitis)
2. Sex (cancer cervix)
3. Race or ethnic factor (black more susceptible for
hypertension)
4. Genetic (sickle cell anemia, thalassemia)
5. Resistance (man is immune against avian tuberculosis)
6. Behavior, life style, diet, personal hygiene, contact with other
person food handling.
Environment (E)
Factors external to the agent or host.
*types of environmental factors
1. Physical: climate (heat, cold) air (pollution), water
(pollution), radiation.
2. Socioeconomic: social status (crowding area without
ventilation, diet) occupation e.g. exposure to chemical agents,
wars, famine, floods, urbanization. Health education
3. Biological: infectious agent's disease, reservoir of infection,
mode of transmission by flies, mosquitoes, air.
*distribution of the disease involves the study of:
1. Person (age, sex, nationality, marital status, social class,
occupation, education).
2. Place: rural, urban, national, international.
3. Time: epidemic, cyclic, seasonal.
Preventive epidemiology
* Epidemiology is dealing with mans status in health and
disease
* If we talk about health we mean mental, physical, social and
psychological well being, we don’t mean absence of disease
only
* Preventive epidemiology: is dealing with how to prevent
disease occurrence and promote good health.
*disease may be: 1. Acute, communicable e.g. cholera
2. Chronic, non- communicable e.g.
Hypertension
1. Acute, communicable, disease:
Is a disease caused by a specific infectious agent (living agent)
or its toxic products.
* Infectious agent is transmitted from a reservoir to a
susceptible host.
Type of transmission: a) direct from infected person or animal.
b) Indirect from intermediate host or
environment.
Incubation period: short (hr, days, weeks)
Etiology: monofactorial agent e.g. bacteria, viruses, fungus.
Cure: usually by medical treatments and certain possible
prevention and control for infectious disease
2. Chronic, non- communicable, disease:
It arises as a result of exposure to certain specific agent that
causes specific disease.
Type of agents: chemical, gases, radiation, allergens
Incubation period: long (months, years)
Etiology: multifactorial.
Cure: usually persist for long time and the majority of them
terminate with death of patient.
Transmission of diseases:
Mechanism of disease transmission:
There are 3 actions (step) for disease transmission:
1. Escape of the agent from the source or reservoir
2. Conveyance of the agent to a susceptible host.
* There are 2 ways of conveyance of agent to susceptible
host
A.)Direct, immediate, where no vectors is involved from
person to person through actual physical contact i.e.
transmission through direct contact between susceptible
host and reservoir (infected person, e.g. gonorrhea,
syphilis.
B.) indirect: involve the use of vector as:
1.) Animate (living e.g. blood sucking arthropod),
transmission occur after incubation period during which
agent multiplies in the arthropod vector.
2.) Inanimate (non- living) which facilitate indirect
transmission e.g. personal articles as keys, pens.
3. Entry through appropriate entry point
Portal of entry:
The path by which infectious agent enter the susceptible
host e.g. respiratory, gastrointestinal.
Portal of exit:
This is the pathway through which infectious agent
leaves the reservoir.
e.g. respiratory : (coughing, sneezing, talking)
- genitourinary: (Foley catheter, sexual transmitted
disease)
- skin, mucus membrane :( wounds, skin breaks, needle
sticks, blood transfusion).
- vertical e.g. :( transplacental transmission).
Type of
disease
Cold
Site of
entry
respiratory
tract
measles
common
serum
hepatits
malaria
Mode of transmission
inhalation of by
infectios
exit
respiratoty
secration
Droplets of
infectious
agent
skin
Intravenous (I.V) or
subcutaneous inoculation
skin broken mosquito sucking infected
insect by
bite
gonorrhea
genital
Person sexual intercourse
syphilis
mucous
person ot
membrane
Typhoid
G.I.T
By ingestion of infected
fever
water, food
Diphtheria
Person To person by
tuberculosis Upper
inhalation of infected
(T.B)
respiratory droplets
tract
* Person to person or serial transfer transmission:
Def: the spread of a disease agent through contact
between infection and susceptible persons.
Examples of disease: measles, syphilis, gonorrhea.
blood
blood
infected
exudates
(stool)
faeces
respiratory
secration
*mode of transmission
The mechanism of transfer of an infective agent from the
reservoir to a susceptible host.
1. Air –born. (Droplet infection) respiratory system.
Organism contained within droplet nuclei or dust
particles. (Droplet nuclei of tuberculosis).
For example if the agents viral in origin affecting the respiratory tract,
e.g. measles, rubella, whooping cough, mumps
If the agent is bacteria in origin e.g. tuberculosis, diphtheria, sore throat
(streptococcus)
2. fecal-oral (gastrointestinal) transmission:
The source is usually contaminated food (milk,
water).flies and fingers are potent routes for
transmission.
Agent is mostly bacterial in origin e.g. typhoid fever,
cholera, bacillary dysentery.
It may also be protozoa or amoebic e.g. amoebic
dysentery.
3. Sexually transmitted (venereal) disease (STDS):
It occurs by closely body contact because agent is
usually killed outside the body e.g. gonorrhea,
syphilis, AIDS.
4. Contact transmission (other than STDs):
This occurs through direct contact through skin or
mucus membrane.
Examples: 1) some dermatological disorders (tenea
vercicolor, herpes simplex by kissing)
2) Eye infection e.g. trachoma by flies or
contaminated finger or towels
5. Animal transmitted diseases (zoonoses):
Where an animal is the mode of transmission.
Example: intestinal T.B. by ingestion of row milk
contaminated by bovine T.B.
6. Insect –borne disease (vector- born):
Examples:
1.) Malaria is protozoa diseases where the
parasite multiplies inside the body of the mosquito to
be mosquito bite.
2.) Yellow fever viruses .external vectorborn transmission by mechanical transfer on external
appendages (feet of flies), so the insect play an
essential role in disease transmission.
7. Vertical transmission:
It occur by transmission of infectious disease from
mother (one generation) to an infant (next generation).
During:
A) Pregnancy (through transplacental way e.g. rubella in the first three
months of pregnancy)
B.)Delivery (through infection e.g. toxoplasmosis, cytomegalovirus)
C.) Breast feeding
*transmission of HIV from mother passes to the baby:
1. during pregnancy through placenta.
2. during delivery through process contact.
3. after delivery through breast feeding
*person to person
_disease agent is transmitted through contact between infected and
susceptible person.
_can spread by means of respiratory, anal, oral, genital routes.
viral Transmitted infection
HIV
Hepatits B
Genital herps
Genital warts
Rubella
Cytomegalovirus
bacteria Transmitted disease
chlamidia
gonrrhea
bacterial vaginitus
trichomoniasis
syphilis
investigation of epidemices
Infectious disease e.g. cholera, typhoid are common in developing
tropical countries. Epidemics are caused also by diseases other than
infectious diseases e.g. chemical food contamination air pollution, lung
cancer.
Steps of investigation of epidemics:
1) confirmation of the diagnosis by clinical and laboratory method.
Aims: A.)To determine the correct cause of epidemic disease for
examples. To differential diagnosis between hepatitis and yellow fever.
The both diseases have the jaundice (yellowish colorations of the eye)
*differential diagnosis between cholera and food poisoning.
*differential diagnosis between meningitis and encephalitis.
B.)To confirm the diagnosis of the cause of the death of the cases.
2) Confirmation the existence of epidemics by presence of large number
of person which have the same complaints of the same case.
3) Description of epidemics:
It means the identification of affected persons and their characteristic
A) With respect to time: it is done by plotting the cases by the time of the
onset of symptom using the epidemics curve.
*Epidemics curve
Incubation period (I.P): It is the time (minutes, hours, days, months, or
even years) between the exposure to agent and the onset of symptomes
and sings of the disease.
Symptoms: are the complaints of patient by his or her words.
Signs: are the objective findings which are seen by doctors, nursing or
paramedicans.
Use of I.P.:
1. Determine the source of infection: for example; small pox the patient
could be asked about the movements and contacts with persons. 7-21
days before he got sick
2. Determine the period of exposure to contacts: it means the period time
equal to the usually incubation period of the infection agent.
3. Immunization: certain disease can be prevented by immunization in
incubation period.
For example: with immunoglobulin (Ig)can be prevented or modify an
attack of measles in child which contact with infection.
4. Prognosis: in some infection, the prognosis is related to incubation
period .the shorter I.P, the worse prognosis e.g. tetanus
Factor that determine the epidemics:
1. Onset of the disease.
2. The specific disease which is characterized by its I.P.
3. The time of exposure to the etiological agent.
B. With respect to place:
It is done plotting the cases by the location of the part of city which they
come from using spot map.
In use of spotmap, case location can by place of residence, place of work
or school attended.
A
C
C. With respect to person:
B
D
It is done by tabulating the distribution of cases by age ,sex, nationality
,occupation, religion, and other characters.
Aims: to determine the pin-pointing the exact population at risk.
4. Determine of individual epidemics histories:
Aim: to allow the classification of exposed persons as to the following.
a. source of the infection
b. whether ill or not ill
c. if ill what is the clinical data, laboratory investigations
(results)which help to diagnosis of case.
A.) case history:
So, take details of each confirmed or suspected cases to obtain
complete picture of the epidemic. It includes the following .age,
sex, and name, and occupation, place of residence, recent
movement, and onset of disease, symptoms and sings of
disease.
B.) Search of additional cases.
5. Study of the environmental condition in the identified
place
e.g. investigation source, method of food preparation and
preservation in the area of restaurants.
6. Study of source of infection and spread of epidemic
This can be done by comparing the percentage of persons
exposed to the suspected source or mode of infection among
those ill and those not ill.
The investigator doctor should be known why the epidemic
occurred and how the stage comes to be set for its occurrence.
-In dry months, human movement may be increase the spread of
the disease such as meningococcal meningitis and influenza
may be facilitated.
-At other times, seasonal changes in the temperature and
humidity at night facilitate transmission of respiratory
organisms among persons sleeping at the room.
-Food supplies or water supplies or housing and sanitation
should be investigation and local health inspector who has some
knowledge of the area is useful person to have on the
investigation team.
- As regard to infectious process should be know on the
following:
1) The agent of disease and its characteristics.
2) The reservoir (man as a case, or carrier, animals, insects,
birds, plants, water or soil).
3. The mode of transmission to the next host.
4. The mode of exit from this reservoir or source.
5. The mode of entry.
6. The susceptibility of the host.
7) Management of the epidemics: it includes the following:
a. treatment of cases.
The doctor who investigation as an epidemic must also
responsibility for treatment of the cases he diagnosis.
e.g. in an epidemic of meningitis , plague or cholera need
emergency care with rapidly well training additional staff.
b. prevention of spread and control measures to plane a
complete control program.
☺many epidemic diseases can be prevented by:
Method of prevention of epidemic
a. immunization
b. isolation of affected individuals and imposition of
quarantine to prevent movement in or out of an area.
c. improvement of health hygiene through health education
d. providing a better water supplies.
e. control of vector breeding or killing of vectors
f. long term plans for continued vaccination after an initial
mass programmed.
c. writing a report:
It is usual to write reports after investigation of an epidemic
Type writing reports:
1. Popular account for laymen.
Aims: a) to understand the nature of epidemic
b) To know the method to prevent spread or
recurrence.
2. An account for planners in the ministry of health.
Aims: to know the necessary steps are taken to limit the
outbreak or prevent recurrent.
3. Scientific report
Aim: to teaching medical staff about medical control.
- During the acute phase of epidemic, it is necessary to
keep the individual at special risk (e.g. contact) under
the surveillance.
- After the epidemic is under control, it is necessary to
keep the immunity under surveillance to detect further
rises in incidence or to insure effective control measure
-keep all links of chain (infectious agent, reservoir,
mode of transmission and level of immunity) under the
close observation.
-sources of information for surveillance:
1. Notification of illness by medical staff, school
teachers or heads of families
2. Certification of death by medical authorities.
3. Data from other source e.g. public health laboratories.
☺morbidity and mortality measures
They reflect the frequency of sickness producing and
death causing diseases in the community.
-Disease rate: it is the number of persons with a
disease per unit of the population of the place interest at
a given time.
Disease rate = N/N+F*100
N: number of person having disease
F: Number of persons without disease
N &N+F come from same population
Morbidity: the frequency of illness in a society
Mortality: the frequency of death in a society
*morbidity rate
Definition: it is the ratio of sick to well person in a society.
*aim for keeping morbidity rate:
1. Help to control infectious or communicable disease by health agencies.
2. To make public program for planning and evolution proposes such as
center for retarded children.
3. To determine the effect of morbidity of workers in various industries.
4. for investigation causes of disease.
*source of morbidity records
1. Disease control activates e.g. tumor registers.
2. Goverment financial public assistance.
3. From data accumulated e.g. by routine hospital and health center
4. from morbidity survey
5. Recordes o industrial and school absenteeism
*errors affecting morbidity and mortality data:
1. Diagnostic inaccuracy.
2. Incomplete identification of cases.
3. Variability of the recording system.
4. Population migration
5. Change in population structure (age, sex, race………….)
6. Change in administrative boundaries related to health serves.
*Incidence rate :number of new cases of disease that occur during a
specific period in a define population
Incidence rate = no. of new cases of disease in population during a
specific time ÷ no of persons exposed to the risk of developing of disease
during the same period *100%
* Prevalence rate: no. of case in a defined population at a particular point
in time or during a specified period
Prevalence rate = no. of total cases (old &new) of disease present in
population at a specific time ÷ no. of persons in population at the same
specific time *100%
Attack rate =no. of total cases (old &new) on one day ÷ no. of actively
exposed persons *100%
Infant mortality rate = no. of death infants under 1 year during a period ÷
no. of live birth during same period*100%
Neonatal mortality rate= no. of death infants under 28days during 1
month period ÷ no. of live birth during same period*100%
Fertility rate= no of live birth in an area during a year ÷ midyear
population aged (15-44) in the same area, in the same age.*100%
Type of human reservoir casing spread of infection in the
community:
1. Carrier
Is well person without appearance sings of disease and move freely
among the peoples? So, the carrier helps the spread of infection.
2. Subclinical sick individual:
A person has a mild sickness which unable to move about freely
3. Frank sick individual (patient):
A person has clinical feature of disease without ability to
movement. So, it is isolated or hospitalized without chance to
contact with well person.
*control and prevention of infectious disease:
1. Control the source of infection.
2. Control channels of transmission.
3. Protecting susceptible individual.
1. Control the source of infection:
First, type's sources (reservoir) of infection may be:
*general measures of control source of infection:
1. Early diagnosis: ensure early detection before epidemic
transmission.
2. Notification: help public health staff to immediate action to
efficient control.
3. Isolation: limiting the spread of disease examples of disease
need isolation cholera, small pox.
4. treatment a.) reduce the infectious disease
b.) prevent the spread of disease
c.) prevent development secondary cases.
5. Quarantine: is the detention of well person or contacts to come
in contact with infectious disease
the period of quarantine equal the longest incubation period of the
*disease
* it is important in the case of international travelers.
*common incubation period – cholera: 5 days
_ Plaque: 6 days
_ Yellow fever: 6 days
6. Surveillance:
*during acute phase of an epidemic
Keep the community
under surveillance to detect further increase (rise) in incidence and
to ensure the effectiveness of selected control measures.
* Best method for surveillance keeps all links of chains.
a.)Agents
b.)reservoir
c.)Mode of transmission
d.)Level of immunity
7. disinfection: should be performed on a.)Concurrent level
b.)Terminal level
a.)Concurrent disinfection: def. means immediate destruction of
infectious material e.g. faecal material, urine, sputum
2. Interruption or blocking channel of transmission:
methodes of transmission of infectious disease:
1. Air borne infection:
*ways (method) of infection
_ by droplet infection
_ By droplet nuclei infection
_ By infected contaminated
dust particles
Examples of air borne infectious diseases:
Common cold,
influenza
sore throat
pneumonias
Pulmonary T.B
measles
mumps
diphtheria
Chicken pox
whooping cough
scarlet fever
*methods of control: what to do
1. Bed spacing
2. Dust control
3. Good ventilation
4. Good health habit
5. Air disinfection
6. Use of masks
7. Decrease over crowding
2. Food and drink borne infection:
*methods of infection:
A.) INGESTION OF CONTAMINATED FOOD, WATER
AND MILK
B.) contaminated infected hands from excreta of patient or
carrier
C.) ingestion of infected meat
D.) house flies
E.)Shell fish if taken from sewage
*example of diseases;
- Dysentery amoebic
- shigellosis
cholera
- ascariasis
- typhoid fever
poisoning
- enteroviruses
- gastroenteritis
- enterobious vermicularis
- amoebiasis
-
- staphelococcal food
-hepatitis A
*methods of control: what to do?
1. Provision of safe and clean water which contain residual
amount of chlorine.
2. Food sanitation
3. Good washing vegetable with clean running water
4. Control flies by using insecticides
5. Sanitary sewage disposal
6. Control restaurant and food handlers
7. Personal hygiene (hand washing and health education)
8. Provision of public health laboratory testing (milk, water,
food and meat
9. Boiling or pasteurized of milk (143̊C
30 min) (163̊C
15 sec)
3. Arthropod borne infection:
*methods of transmission of infection:
A.) by inoculation of insect bite.
B.)By contamination of skin wound or mucus membrane.
C.)By infective feaces of the vector.
D.) By infective body fluids of vector when crushed.
* Types of vectors and examples of disease:
1. flies: enteric fever
gastroenteritis
typhoid fever
bacillary dysentery
2. Louse: epidemic typhus
relapsing fever
3. Fleas: plaque
endemic typhus
4. Mosquitoes: malaria
filariasis
yellow fever
dengue fever
*methods of control:
1. Use of fly swatter, insecticide, electric insect killer
2. Screened window
3. Clean lines
4. Avoid over crowding
5. Avoid collection of dust in room
6. Elimination of mosquito breeding places.
7. Use of mosquito nets and fan for sleeping.
4. Contact transmission infection:
*methods of transmission:
A.) By direct or indirect contact with infected lesion.
B.) by sexually transmitted
*examples of infectious disease:
1. Bacteria: T.B. of skin
gonorrhea
2. Viruses: herpes simplex viruses
papilloma viruses
AIDS
human
3. spirochates: syphilis
4. Fungus: tinea capitis
scabies
Trachoma
Madura foot
tinea pedis
eye infectious disease
moniliasis
actinomycosis
*methods of control for sexually transmitted diseases:
1. Suitable medical treatment
2. Avoid illegal sexual intercourse
3. Strict personal cleanliness
4. Prevent the use of infected material used by patient.
5. Health education.
3. Protecting susceptible individual
*methods of protection:
1. by immunization
2. Good vitamin-A for health skin and cornea
3. Good nutrition increase resistance to infection
4. Good health hygiene to avoid measles or other infectious disease.
5. Avoid the exposure to allergen to prevent the start of allergic disease
Control of chronic diseases
In development, industrialization countries, infectious diseases give way
to chronic diseases (epidemiological transmission from infectious to noninfectious) this called disease of civilization.
- Cancer
-angina pectoris and myocardiasis
disorder infraction
- occupational hazards
- mental
-industrial and road traffic accidents.
It is time now to being to put down and translate into action appropriate
strategies for prevention.
Levels of prevention and control of chronic diseases
1. Primary prevention
A. health promotion
B. Specific protection
A. Health promotion
Aim: improving the general health of individual and community
Methods:
1. Increasing nutrition
2. Increasing environmental sanitation
3. Increasing personal hygiene
4. Health education
5. Socioeconomic development
6. Genetic counseling
B. Specific protection
Aim: Limit risk factor
Methods:
1. Protection against
Risk factors in chronic disease:
Aim of primary prevention: Decrease risk factors in chronic diseases
Type of risk factors: 1. Endogenous
2. Exogenous
1. Endogenous risk factors
 Life style: * eating habit
*Smoking
*customs
*spending leisure time
*exercise or not
*genetic inheritance
*age, sex, race, nationality.
 Environmental: _ geographic variation
_ Seasonal variation
_ Air pollution
_ Unsuitable exposure
Examples of endogenous factors causing diseases
Risk factors:
Smoking
Diseases
Chronic bronchitis
Cancer of lung
Obesity
Diabetes mellitus
Hypertension
Coronary heart diseases
Air pollution
Bronchial asthma
Emphysema
bronchitis
Un suitable exposure
Cancer of bladder
2. Secondary prevention
Definition: Any action with early detection and treatment the
disease before the appearance of permanent damage
Diseases of civilization:
Definition: large reservoirs undiagnosed chronic diseases in the
community.
* It takes long incubation period without the appearance of
symptoms
Methods of control
1. Screening method of early detection of diseases.
e.g early detection cancer unit for detection of precancerous
lesion.
2. Periodic sampling from workers with high risk groups some
diseases
e.g Silicosis, asbestosis
3. Follow up the positive cases with further diagnostic evaluation
and treatment
3. Tertiary prevention
Aim: A. adequate treatment of diagnostic diseases
B. limit of disability
C. Prevent of further complications or death
D. rehabilitation by the following:
1. Physical therapy: e.g. restoration of skeletal muscle function
EX. Muscular exercise for atrophy of muscle after long bandage or in
poliomyelitis
2. Occupational therapy: by restoration the capability to earn a living.
3. Social and psychological rehabilitation: by restoration of personal
confidence, and social and family relationship.
Risk factors and preventive control to some chronic diseases
1. Ischemic heart disease
Risk factors:
1. Area with soft water supply
2. Diet rich in saturated fatty acid.
3. Hypertension
4. Smoking
5. Obesity
6. Competitive personality
7. Physical inactivity.
Control and prevention method
1. Periodic screening to discover people with one or more risk factor.
2. Then treatment for removal or decrease risk factor.
2. Coronary heart diseases
Risk factors:
1. Diet rich in saturated fatty acid and cholesterol.
2. Hypertension
3. Smoking
4. Diabetes mellitus.
5. Physical inactivity
6. Male sex
7. Oral contraceptive pills
8. Behaviour, pattern of personality.
9. Physical and social environment (cold and stress).
3. breast cancer
It is most common cause of female cancer in Saudi Arabia
Risk factors:
1.
2.
3.
4.
5.
6.
7.
Age.
Low parity.
Late menopausal age.
Higher social class.
Fat consumption.
Age at menstruation (early menstruation is risk).
Family history of breast cancer.
Prevention and control:
1. secondary prevention can reduce mortality rate
2. Screening procedure can detected premalignant and early cases for
cancer.

A.
B.
C.
Methods of screening
self breast examination
Routine breast examination by doctor.
Mammography for female up to50
4. Cancer cervix
Cancer cervix has less incidence of cancer death in Saudi Arabia than
cancer breast.
Risk factors:
1. low social class
2. early age at marriage
3. multiple sexual partners
Control and prevention
1. periodic screening of cervix cytology
2. decrease risk factors
3. Early detection and treatment of precancerous lesion especially
carcinoma in situ.
5. Hypertension
Hypertension is a risk factor for the following diseases:
1. Stroke
2. Coronary heart disease
3. Congestive heart failure
Risk factors
1.
2.
3.
4.
5.
Genetic inheritance.
endocrine disorder
excessive salt intake
obesity
smoking
Prevention and control:
1. screening method for early detection cases
2. decrease risk factors
3. medical treatment
Epidemiologic principles in intensive care unit (ICU)
Causes of seriously ill ICU patient
1. Patient with marked decrease defensive mechanism.
2. ICU patient are usually consider as emergency condition with more
susceptible for infection.
3. Patients or other workers in units are more susceptible for cross
infection or contact infection.
4. ICU often become reservoirs of antibiotic resistance
microorganisms that may be are difficult to eliminate.
Sources of infection in ICU:
1. Exogenous infection * hospital staff in ICU.
* Instrument in ICU.
2. endogenous infection from patient it self with altered flora e.g flora
in pharynx
3. patient it self act as source for other patients in ICU or for staff
members
Some of epidemiological bacterial infection in ICU:
1. staphylococcal infection:
Are usually with contaminated instruments or environmental sources.
2. streptococcal infection:
Are usually with wound infection and usually come from human
sources colonized in throat or perineum
3. G-ve bacilli:
Are usually transmitted by 2 way * faecal oral route of infection
* Hands carry the infection (carrier state
of infection)
4. contamination with favourable site of growth and proliferation
in ICU
Examples: - respiratory nebulizers or tubing e.g pseudomonas
- IV fluid e.g 1. klebsiella
2. enterobacters
Defining the problem by calculation the rate of infection
 Rate of infection = no of infection of specific type /no of patient
risk at same time * 100
 Rate of infection differed from one unit or hospital to another in
well defined group of patient depend on the following.
No of patients
October (30)
November (40)
Urinary tract infection
3 (10%)
10 (25%)
Pneumonia
6 (20%)
7 (17.5%)
Rate of pneumonia in October= 6 *100/30=20%
Factors determine variations rate of infection:
1. Age of patients.
2. Major complications.
3. Prognosis of specific type of disease.
For example: * incidence of urinary tract infection follow
catheterization.
*incidence of wound infection for specific type of
surgical operation
4. Predisposing conditions for infection.
5. Risk of specific disease such as renal disease or
cardiopulmonary diseases.
Control and management of infection in ICU
General recommendation:
1. Hand washing
A. hand washing of all patients contact.
B. use antiseptic for easily hand washing.
C. wears gloves for high risk patient contacts.
2. Spacing patients:
A. sufficient space around each patient to decrease infection transmission
by direct contact.
B. no overcrowding of patients or instruments.
C. good ventilation.
3. Isolation in ICU
Prepare infection space for infected patients
4. Aseptic techniques for the following procedure:
A. IV fluid
B. urinary catheterization cannel
respiratory in tubing D. cut downs or others
C.
5. Limitation of visiting to ICU
Aim: decrease number of visitors to decrease transmission of infection to
patients.
6. Cleaning
A. good cleaning of surface daily with clean cloths.
B. removal immediately all spills blood or blood products or other fluid
by antiseptic solution.
C. daily cleans the floor.
Examples of complete sterile procedure in ICU:
1. Catheterization – urinary catheter
- IV catheter
2. Inhalation therapy
3. Tracheotomy
4. Wound care (sterile surgical dressing)
Supervision and services training in ICU:
Aims:
1. To ensure proper hand washing, cleaning the device.
2. Training of ICU personals for new instruments.
3. Fresh seminars to sure the techniques are done under complete sterile
condition.
4. to ensure smooth work flow with ICU patients and staff members.
Spectrum of the disease
This is the sequence of events that occur in the host (human organism
from the time of exposure to an etiological agent till recovery or death)
On exposure to agent, it may take sometime for the manifestation of the
disease to develop. Manifestation of the disease may be severed or mild,
the disease maybe end up recovery or death. This depends on the:
1. The nature of the disease, some disease may have good prognosis
(pharynitis) or bad prognosis and death (malignancy).
2. The availability and efficacy of preventive or therapeutic measures,
if introduced at a particular point of the spectrum, will completely
prevent or retard the development of the disease.
*gradient of infection is the spectrum of the infectious; it reflects the
response of the host to the infectious agent.
*manifestation of the disease may be:
1. Subjective: feeling of a complaint (headache), this is called symptom.
2. Objective finding of the disease (skin rash) are called sign.
Theories that describe the occurrence of the disease:
There are various theories to describe this relation.
1. miasmic theory:
Day miasma (pollution) is linked with many chronic disorders, e.g.
respiratory, malignant
2. Humeral theory:
An excess or deficiency of any physiologic (disease of puberty as acne),
metabolic (diabetes mellitus) or nutritional (obesity) agent can result in
disease occurrence.
3. psychological theory:
Emotional instability may worsen the people health; they impose body
weakness so become susceptible to disease.
4. germ theory:
This is the most important theory describe most of the disease occurrence,
bacteria, viruses….cause many disease.
5. epidemiologic theory:
This theory claims more one factor to be responsible, it attributes many
factors; it denotes a multifactor nature of the disease.
Screening
Screening is important in preventing chronic disease. Its main role is in
secondary prevention where it acts by disclosing the disease at an early
stage.
There are several screening test to be tried to control the progress of the
disease.
Screening test
condition
Chest x ray
Lung cancer
Heart disease
Serological test
Syphilis
HIV
Blood sugar
Diabetes
Serum cholesrerol,triglycerides(lipd
profile)
Hypercholesterolemia
Atherosclerosis
Electrocardiogram (ECG)
Heart disease (ischemic, arrhythmia)
Blood pressure
hypertension
Vaginal swab
Cancer cervix
Sputum (bronchial washing)
Lung cancer
mammography
Breast cancer
Some examples of infectious diseases
1. influenza
Acute infectious disease caused by type A , B and C influenza viruses
with generally uncharacteristic catarrhal systemic symptoms and a
tendency to bacterial complications.
Incubation period: 1-2 days
Transmission: predominantly droplet infection.
Symptoms / course: *onset marked by general malaise, chills,
temperature rise.
* Occasionally, vomiting and diarrhoeal.
Disease course and severity highly variable, depending on type of
influenza virus and interaction with other pathogenic organisms.
Diagnosis:
The virus can be isolated from throat washings until the forth day of
the disease by culture on embryonated egg or tissue culture.
Therapy:
 Brief bed rest in febrile stage.
 Inhalation and ingestion of hot tea also help.
 Antibiotics only in patients with risk factors (old age, reduced
resistance, renal insufficiency, (cirrhosis of the liver)
 Penicillin, amoxicillin, tetracycline, erythromycin, oral
cephalosporin are suitable for prevention of secondary bacterial
infections.
2. Cholera: Enterocolitis- Entrritis
 Acute water transport disturbance of intestinal wall with
diarrhoeal and vomiting and large water and electrolyte losses
caused by the toxin of vibrio comma (cholera).
 Incubation period: 1-3 days, occasionally a few hours only.
 Transmission: contact with patients or vibrio carriers or by
contaminated drinking water, milk, or foods.
Symptoms/ course: sudden onset of diarrhea with vomiting, the
stool becomes pultaceous and then rapidly thins, a rice water_
like consistency. Sever dehydration.
 Diagnosis: demonstration of causative organism in fecal smear.
 Therapy: the first requirement is for adequate infusion therapy
with glucose contains electrolyte solutions.
For patients already in shock, treatment is problematical.
Oral replacement may be beneficial under primitive conditions.
3. Scarlet fever
Tonsillar infection caused by beta –haemolytic streptococci
(streptococcal sore throat) with characteristic toxin induced rash.
Incubation period: 2-7 (22) days, in wound scarlet fever, hours.
Transmission: usually droplet or smear infection but also foods (milk,
ice cream).
Portal of entry: tonsils, nasopharynx, wounds.
Scarlet fever patients are the sources of infection (until
convalescence):
Nasopharyngeal –optic secretion.
Symptoms/course: initial phase 3-7 days, sudden onset with high
fever, chills, sort throat, vomiting .all transitional stages from
streptococcal sore throat to scarlet fever, possible (acute pharyngitis).
Regional lymph node swelling, initially white- coated tongue, and
starting on the 3rd day typical (strawberry tongue).
Scarlet fever rash: during 1-2 days closely spaced pink to flaming
small spots, circumoral pallor.
In second week, desquamation, branlike in face and on trunk, coarsely
lamellar on hands and feet.
Observation for 3 weeks necessary.