part 1 f undamental c oncepts in p ublic h ealth and t ropical m edicine
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PART 1FUNDAMENTAL CONCEPTS IN PUBLIC HEALTH AND TROPICAL MEDICINE
LEARNING OBJECTIVES
1. Explain environmental health engineering aspect in public health and tropical medicine
2. Identify and describe dissemination of infectious disease related to water
WHAT IS PUBLIC HEALTH?
QUESTION: WHAT’S AN EPIDEMIOLOGIST?
a) A disease detectiveb) A skin doctorc) A scientist who studies the epicenter of disaster
sitesd) A scientist who studies epiphyte plants, such as
orchids or ferns
PUBLIC HEALTH ‘POLICE POWERS”
Inspections & closures Licensing & discipline of health professionals
& facilities Quarantine & isolation Vaccination, testing and treatment
requirement Seizure, embargo and impounding of unsafe
substances
PUBLIC HEALTH CONCEPT
Important major areas of public health: Health Services Epidemiology Social/Behavioral Science Environmental Health Biostatistics
PUBLIC HEALTH CONCEPT
Important major areas of public health: Health Services
Deals with diagnose & treatment of diseases Epidemiology
Study the causes of illness and distribution of disease in populations.
The science behind public health – study disease control & prevention.
Social/Behavioral Science Deals with human psychology, economics, history,
and anthropology. Focus to describe, understand, predict, and change the public's health
PUBLIC HEALTH CONCEPT Important major areas of public health:
Health Services Epidemiology Social/Behavioral Science Environmental Health
Deals with all environmental aspects (physical, chemical & biological) that impact human health. Involve assessment & control of these environmental factors to prevent disease & improve health
Biostatistics Application of statistic in area of biology via data
collection, analysis and interpretation. applied in public health including epidemiology,
health services research, nutrition, and environmental health
MAJOR TYPES OF PUBLIC HEALTH ACTIVITIES
Surveillance Outbreak investigation Reference diagnosis and consultation Research (bench-to-field-to-prevention) Technical assistance & training (lab & epi) Initiate & support implementation projects Health policy and Health communication [Philosophically founded on Epidemiology]
PUBLIC HEALTH SURVEILLANCE
Definition: The ongoing systematic collection, analysis, interpretation, and dissemination of health data = Information for Action!
Detect changes in disease occurrence and distribution
Detect changes in agent or host factors Detect changes in health care practices Follow trends and patterns of disease
TYPES OF SURVEILLANCE
• Passive Surveillance: Reports are sent to the health department
based on known rules and regulations • Enhanced Passive Surveillance:
The health department distributes information on a particular disease and asks for reports
• Active Surveillance: The health department calls or visits a
location to collect reports • Sentinel Surveillance:
A pre-selected sample of potential data sources submit information
SURVEILLANCE SYSTEM Hospital syndromic
surveillance Syndromes Diagnostic tests Bed and ventilator
availability Prescription
pharmaceutical stocks/usage
School surveillance Absenteeism Syndromes
Reportable disease surveillance
Environmental surveillance
24/7 phone duty Death surveillance
Pneumonia and influenza
Unusual deaths Death certificates
OTC pharmaceutical surveillance
EMS surveillance ELCIDS food-borne
disease surveillance
PUBLIC HEALTH VS. MEDICAL CARE
The concept of Public Health differs from the concept of individual medical care, and the
skills are very often different
Public Health deals with populations, prevention and policy, and includes research on all of these.
Public Health often involves the treatment of individual patients, but that is NOT its focus, but rather populations at risk
OUTBREAKS/EPIDEMICS
Definition: The occurrence of more cases of disease than is expected in a given area over a particular period of time.
The term epidemic often implies a larger number of cases over a wide geographic area
STEPS OF AN OUTBREAK INVESTIGATION1. Prepare for field work2. Establish the existence of an outbreak3. Verify the diagnosis4. Define and identify cases
1. Establish a case definition2. Identify and count cases
5. Perform descriptive epidemiology6. Develop hypotheses7. Evaluate hypotheses8. Reconsider/refine hypotheses and conduct
additional studies9. Implement control and prevention measures10. Communicate findings
GOALS OF AN OUTBREAK INVESTIGATION Describe the outbreak:
person, place, & time Determine disease
characteristics Specific agent Pathogenicity Incubation period Communicability
Identify modes of transmission Person-to-person Airborne Common source (food
or water) Zoonotic Vectorborne
Identify additional cases and contacts
Identify the source of infection
Interrupt disease transmission—present and future
TYPES OF OUTBREAKS
• Common source: everyone’s exposed to the same thing Point source: the exposure occurs all at once Intermittent or continuous: the exposure continues
over a period in time
Propagated: disease spreads gradually from person to person
Mixed: common source + person-to-person spread
• Other: zoonotic or vector-borne diseases
PUBLIC HEALTH MEASURE TO CONTROL EPIDEMIC
Control directed against the reservoir-animal, insect reservoir can be effectively control by eliminate them
PUBLIC HEALTH MEASURE TO CONTROL EPIDEMIC
Control directed against transmission of the pathogen:-
if via water/food, then public health procedure can be instituted to prevent contamination or destroy the pathogen in the vehicles.
Water purification help to reduce incidence of typhoid fever, pasteurized milk reduced bovine TB.
Devise food protection law to prevent enteric pathogen to human.
Respiratory transmission is difficult to prevent, wear mask, but this is not effective method as it’s voluntary measure.
PUBLIC HEALTH MEASURE TO CONTROL EPIDEMIC
Vaccination-tetanus, small pox, diphtheria, whooping cough, polio myelitis have been eliminated.
Adult inadequately immunised against childhood disease- low titre of Antibodies as immunity gradually disappear with age., so tetanus vaccine to be given every 10yr
PUBLIC HEALTH MEASURE TO CONTROL EPIDEMIC
Quarantine- involve limitation of freedom of movement of individual with active infection to prevent spread of disease
PUBLIC HEALTH MEASURE TO CONTROL EPIDEMIC
International agreement, 6 diseases are quarantinable: smallpox cholera typhoid fever plague yellow fever relapsing fever
Do you know these public
health workers?
PART2 : TROPICAL MEDICINE
Branch of medicine deal with unique problems (difficult to control & widespread)
in tropic & subtropic region. Many infections & infestation are classified
as “tropical disease” Used to be endemic in temperate/ cold weather
countries Many can be controlled & eliminated due to
improvement in housing, diet, sanitization & personal hygiene.
WHAT IS DISEASE?
•Disease (due to an infectious agent) is what may happen while your immune response tries to control an infection;
•Disease may be the final outcome if your immune system either fails, or over reacts.
•Infection does not necessarily equal disease
•Infectious disease: disease caused by replicating agent transmissible to human from other person, animal or environment
DISEASE
TERMINOLOGY
Prevalence Proportion (%) of diseased individual in a
population at any one time
Incidence Number of disease individual in a population at
risk
Epidemic Disease when occur in an unusually high number
in a community at the same time
Pandemic Widely distributed epidemic
Endemic Disease that is constantly present in a population,
usually at low incidence Pathogen may no be highly virulent Majority of people is immune Though, few individual may suffer and remain
reservoir for the infection
Outbreak Disease occur when a number of cases observed
ina relatively short time
Mortality Incidence of death
Morbidity Incidence of disease in populations and
include both fatal and nonfatal diseases. Statistically more precise to tell the health of
a population compare to mortality- as major cause of illness is quite different than a major cause of death.
EPIDEMIOLOGIC TERMS WE NEED TO KNOW
Incidence of infection Rate of infection (# new cases/year)
Prevalence of infection Proportion of population infected (%)
Intensity of infection Level of infection (# worms/patient) Severity of infection (morbidity/mortality)
Infectious disease Surveillance Systematic collection, analysis and use of data
on a given infectious disease
STAGES OF DISEASEIn term of clinical symptom, typical course of disease can be
divided into 6 stages:
1. Infection – organism lodged in the host2. Incubation period- time of infection and appearance of
symptoms. Length can be short/long depends on inoculum size, virulence of pathogen, resistance of host and distance from entrance site to the focus infection site
3. Prodromal period-a short period where 1st symptoms such as headache and feeling of illness appear
4. Acute period- disease at its height, with overt symptoms such as fever and chills
5. Decline period- symptom is subsiding, temperature falls, followed by intense sweating and feeling of well-being
6. Convalescent period- patient regains strength and return to normal.
During later stage of infection cycle, immune mechanism of the host becomes increasingly important. Recovery is normally due to these immune mechanism.
CAUSE OF DEATH WORLDWIDE
LEADING INFECTIOUS KILLERS WORLDWIDE
LEADING CAUSE OF DEATH
Health burden to nation
DEATH DUE TO DISEASE (USA DATA)
DEATH DUE TO WHOOPING COUGH (UK DATA)
EMERGING INFECTIOUS DISEASE
1.SARS
2. West Nile disease
3. Variant CJD disease
4. Monkey pox
5. Ebola and Marburg viruses
6. Dengue
7. Influenza H5/N1 (?)
8. Hanta virus
9. E. Coli O157:H7
10. Antibiotic-resistant Pneumococci S.aureus (MRSA) Gonococci Salmonella
11. Cryptosporidium
12. Anthrax
13.Spanish flu
14. Dengue & DHF
EMERGING INFECTIOUS DISEASE (AIDS-RELATED)
1. Pneumocystis carinii pneumonia
2. Tuberculosis
3. Mycobacterium-avium complex
4. Kaposi’s sarcoma (HHV-8)
5. HSV-2
6. Cryptosporidium
7. Microsporidium
8. Cryptococcus neoformans
9. Penicillium marneffei
10. Disseminated salmonella
11. Bacillary angiomatosis (Bartonella henselae)
12. HPV
FACTORS LEADING TO EMERGING OF INFECTIOUS DISEASE AIDS Population growth Speed and ease of
travel Dam building Global climate
change Increased antibiotic
use for humans and animals
Encroachment of human populations on forest habitats
Industrial commercial agriculture
War and social disruption
Relocation of animals
Growth of daycare Aging of the
population Human-animal
contact
DISEASE RESERVOIRS
Reservoir-sites at which viable infectious agent remain alive and from which infection of individuals may occur.
LIST OF HUMAN DISEASE AND ITS RESERVOIR:
• Anthrax – cattle, swine, goat, horse, sheep• Salmonellosis-poultry, egg, water polluted with
sewage• Botulism- soil, contaminated food• Giardiasis-beaver, marmot, water polluted with
animal feces• Malaria-Anopheles mosquito• Plague-wild rodent• Psittacosis-parrot, pigeon, birds• Rabies-wild & domestic carnivor• Respiratory disease- human carrier• Syphilis, goinorrhea, AIDS, STD- human• Tetanus- soil, intestine• Tuberculosis-human, dairy cattle• Typhoid fever -human
Some pathogens are saprophytic- ie live on dead matter. eg. Clostridium tetani in soil
For epidemiologist- interest in pathogen live on living matter
List of human disease and its reservoir
Example of how epidemiological research is performed- Epidemiology of AIDS
TRANSMISSION
Involves 3 stages: escape from host travel entry into a new host
CARRIERS infected individual not showing obvious sign of clinical
disease. Potential cause of infection to others Acute carrier- individual in the incubation period of
disease, then follow by development of the infection Chronic carrier-individual who had a clinical disease
and recovered, or may have subclinical infection that remained in apparent throughout.
Identify carrier by X-ray, immune test, cultural 2 diseases with significant carrier- typhoid fever and
TB (usually food handler) eg. Typhoid Mary in early 1990s
MODES OF INFECTIOUS DISEASE TRANSMISSIONEpidemiologist follows the incidence of disease by
correlate geographical, seasonal and age-group distribution of a disease with possible modes of transmission.
If disease is limited to a restricted geographical location- it may suggest vector, eg. Tropical region, malaria via mosquito vector
If disease is limited by seasonal- often indicate mode of tramsmission eg. Measles, chickenpox for school children and close contact
Age distribution- important for statistic to eliminate particular routes of transmission
Different pathogen, have different mode of transmission- usually related to the habitat of the organism in the body
Eg. Respiratory pathogen is usually airborne, intestinal pathogen usually, waterborne/ food borne
DIRECT HOST-TO –HOST TRANSMISSION
infected host transmit disease to a susceptible host route can be respiratory (cold, flu), direct contact
(syphilis, gonorrhea), skin direct contact (staphyloccus causes boil, pimples) or fungi (ringworm)
INDIRECT HOST-TO-HOST TRANSMISSION
occur by living/ inanimate means living agent transmit disease is called vector- usually
anthropods (insect, mites or fleas) or vertebrates (dog, cats)
Anthropods only carrier of agent from 1 host to another , not a host for the disease- via biting
Some pathogen replicate inside anthropods (this consider an alternate host) and build up inoculum
Inanimate agent- bedding, toys, books, surgical equipment- which come in contact with people can also transmit disease. This inanimate object is refer to fomites
Food and water are referred to as disease vehicles.
CAUSATIVE AGENTS OF DISEASE
biological- bacteria , virus, protozoa, helmith and fungi, prion
chemical- pesticide, petroleum product, cleansing agent physical- sun UV, X-ray equipment, too little of something- lack of Vit. D cause rickets, lack of
niacin cause kwashiorkor too much of something- excessive food or water can be
fatal, excess CO2 in respiratory can cause fatal hereditary- haemophilia, baldness, poor eyesight stress-emotional disorder, stroke, heart attack disease of unknown cause- many die due to environmental
pollutant working synergistically with other factors. Eg. cancer
CAUSATIVE AGENTS OF DISEASE
Biological, Chemical and Physical cause of disease are spread through air, water, food, insect, fomites (fork, doorknob etc) and animal.
In Environmental health, many programmes address the need to control the causative agent while it is in the environment before it get into the public and cause disease.
PORTAL OF ENTRY
Skin- epidermis provide defence vs. pathogen entry, if cut occur, pathogen may allow in
reproductive organ- penis, uterus and ovaries –require body contact, STD- prevention by prophylactics or abstention from sex
respiratory tract (nose, bronchi, aveoli)- TB, pneumonia, strep, human nose has hair to filter pathogen, cilia, mucus to prevent it
Digestive tract- mouth, aesophagus, stomach, small intestine and large intestine- HCL secreted in stomach kill some germ, bile has an antiseptic power because eof its high pH
HUMAN DEFENCE AGAINST DISEASE
1st line of defence (ENVIRONMENTAL MANAGEMENT)- prevention. Apply technology and art of science to control causative agent of disease in environment before it gets to human. This use the environmental health element
2nd line of defence (PUBLIC HEALTH & PREVENTIVE MEDICINE)-based on human body adaptation to prevent agent of disease. This include skin, mucous membrane, cilia, tears- so, proper nutrition, good personal health practise, routine check up
3rd line of defence (PUBLIC HEALTH &PREVENTION MEDICINE)-if the 2nd defence are not sufficient to prevent the entrance of pathogens, then use immunity (active and passive) and phagocytosis (natural- leukocytes destroy pathogen in blood).
4th line of defence (CURATIVE MEDICINE)- when sick, need surgery-medication.
THE 1ST LINE OF DEFENCE VS. DISEASE Water quality
management Human waste
disposal Solid and hazardous
waste management Rodent control Insect control Milk sanitation Food quality
management Occupational health
practice – assure healthy and safety of worker
International travel sanitation
Air pollution control
Water pollution control Environment safety &
accident prevention Noise control Housing hygiene Radiological health
control Recreational sanitation Institutional
environmental management- prevent nosocomial infection
Land use management Product safety &
consumer protection Environmental
planning
2nd LINE of DEFENCE vs. DISEASE:
Host defenses: physical, chemical, anatomical barriers:
HPR173rd LINE OF DEFENCE:
nonspecific defenses (passive defenses; innate immunity) – respond to any invader • natural barriers, antimicrobial compounds• phagocytes (neutrophils or polymorphonuclear leukocytes, PMNs)• complement • natural killer cells (NK cells)
specific defenses (adaptive immunity) – respond to a specific invader• cell-mediated – cytotoxic T cells, activated macrophages• humoral - antibodies
cytokines, chemokines – small proteins; coordinate, modulate
Host immunity: the ability of higher organisms to resist infection
blood and lymph systems
extravascation:
HPR23
bacteria
phagocytosisphagocytosis::
PMNPMN
nucleus
lysosomebacteria are engulfed in phagosome of PMN
phagosomefusion of phagosome and lysosome
degradation of bacteria within phagolysosomerelease of bacterial
fragments to external environment
HPR24
• several pattern recognition molecules (PRMs) on PMN membrane (aka Toll-like receptors (TLRs))
• recognize a pathogen-associated molecular pattern (PAMP)
• e.g., TLR-4 recognizes bacterial LPS
Innate host defenses:
• natural host resistance – some organisms more sensitive to infection by given pathogen than others
• age – very young, very old individuals are most susceptible
• stress – fatigue, exercise, dehydration, large climate changes, stress-related hormone release, suppression of inflammation; predispose to infection
• diet – alteration may influence normal microbiota, decrease resistance, alter susceptibility
• physical, chemical, anatomical barriers – may prevent successful infection when integrity is intact
• tissue specificity – pathogen must contact environment suited to its needs, for successful infection
compromised host: one or more resistance mechanisms inactive; susceptibility increased• suppressed – e.g., drug therapy-induced versus compromised – e.g., AIDS
3rd LINE OF DEFENCE (continue)
ZOONOSES disease that occur primarily in animal, but
occasionally transmitted to human. Since public health for animal is less, infection rate for
these disease in animal is very high. Transmission is animal to animal. Occasionally animal to human. Thus, to control
zoonosis in human is not good approach to eradicate it from animal reservoir.
Success case for zoonosis control are bovine TB and brucelosis via pasterisation of milk.
Some have more complex life cycle. Eg. Protozoa (malaria) and metazoans(tapeworms). So, contol in human or in the alternative animal host.
INFECTIOUS DISEASE RELATED TO ANIMAL CONTACT
NOSOCOMIAL INFECTION
Hospital acquired infections Cross infection from patient or hospital personnel and vice versa
present a constant hazard Hospital are hazardous because
1. many patients are weakened resistance to disease 2. reservoir for highly virulent pathogen3. Crowding of wards4. much movement of hospital personnel from patient to patient5. hospital procedure such as catheterisation, hypodermic
injection, spinal puncture, removal of tissue/fluid/biopsy carry risk of introducing pathogen to patient
6. In maternity ward, infant immune system usually susceptible to infection
7. surgical procedure is major hazard, body exposed to source of contamination
8. drug for immunosuppressant (organ transplant patient) increase susceptibility to infection
9. use antibiotic to control infection carry risk of resistant strain (MRSA)
HOSPITAL PATHOGEN E.coli as most causes for Urinary tract infection, others are
yeast Candida albican, Psedomonas aeruginosa, enterococcus
Staphylococcus aureus - associated with skin, surgical, and lower respiratory tract- problem for newborn baby
S.aureus habitat is in nasal passage – as normal flora. So, in healthy personnel show no disease, but once infected the susceptible patients may cause serious infection
Pseudomonas aeruginosa- causing infection of lower respiratory and urinary tract. Also cause infection in burn patients (where patient loss barrier to skin infection) It is drug resistant, so difficult to treat.
WHAT ARE THESCARIEST INFECTIOUSTHREATS?
Bioterrorism (anthrax; sm’pox; etc.
Pandemics (influenza; plague;..)
Can you say: BIRD FLU ???
Nosocomial Infections
Ebola; SARS; Lyme; Hanta; Cryptosp; Cyclospora; E. coli 0157/H7
POSSIBLE AGENTS OF BIOTERRORISM
POTENTIAL BIOTERRORISM AGENTS
Category A: (anthrax, botulism, plague, smallpox, tularemia, VHFs) can be easily disseminated or transmitted from
person to person; result in high mortality rates and have the
potential for major public health impact; might cause public panic and social disruption;
and require special action for public health
preparedness
POTENTIAL BIOTERRORISM AGENTS
Category B: (ricin, food/water threats, brucellosis, Q fever, etc.) are moderately easy to disseminate; result in moderate morbidity rates and low
mortality rates; and require specific enhancements of CDC's
diagnostic capacity and enhanced disease surveillance.
POTENTIAL BIOTERRORISM AGENTS
Category C: (emerging infections like Nipah virus and hantavirus) availability; ease of production and dissemination; and potential for high morbidity and mortality rates
and major health impact.
CHARACTERISTICS OF BIOTERRORISM Presentation of a rare and serious disease Presentation of rare and serious symptoms Large number of people seeking care for
nonspecific symptoms Unexpected rapidly increasing disease
incidence Disease clusters w/a common source of
infection Endemic disease rapidly emerging at an
uncharacteristic time or in an unusual pattern
Low attack rates for people who stay indoors Sudden increase in mortality
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